COVER: Lateral view of a male snow scorpionfly, Boreus insulanus Blades (Mecoptera:

Boriedae). Adults of this species, like others in the family, are about 4 mm in length,

flightless, and are active during the winter months. At present, Boreus insulanus is known

only from 3 locations on southern Vancouver Island, suggesting that it may be an endemic

species.

Boreus species are found primarily in mountainous terrain, between 200 m and 2000 m

elevation, throughout the Holarctic. In North America, the greatest diversity of species is in

the region from Oregon to Alaska and east to the Rocky Mountains.

Original line drawing by David Blades, published in the species description in Volume 99

of the JESBC (2002).

The Journal of the Entomological Society of British Columbia is published annually in

December by the Society

Designed and typeset by Ward Strong and David Holden.

Printed by Reprographics, Simon Fraser University, Burnaby, BC, Canada.

Printed on Recycled Paper.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Journal

of the

Entomological Society

of British Columbia

Volume 100 Issued December 2003 ISSN #0071-0733

Directors of the Entomological Society of British Columbia, 2003-2004.............ccceeeeeeee 2

Corbet, P.S. A positive correlation between photoperiod and development rate in summer

species of Odonata could help to make emergence date appropriate to latitude: a

testable My POLMCSIS cctematce eceeeca ter cron eeere seat eee tee tte ony eet eee ee ees 3

Heeley, T., R.I. Alfaro, L. Humble and W.B. Strong. Distribution and life cycle of

Rhyacionia buoliana (Lepidoptera: Tortricidae) in the interior of British Columbia..19

Maclauchlan, L.E., L. Harder, J.H. Borden and J.E. Brooks. Impact of the western balsam

bark beetle, Dryocoetes confusus Swaine (Coleoptera: Scolytidae), at the Sicamous

Creek research site, and the potential for semiochemical based management in

altemmative Silviculture: SVStCnmnS 27. x ssers cet oeces seen eee ee 2),

Gillespie, D.R., R.G. Foottit, J. L. Shipp, M.D. Schwartz, D.M.J. Quiring, and Kaihong

Wang. Diversity, distribution and phenology of Lygus species (Hemiptera: Miridae)

in relation to vegetable greenhouses in the lower Fraser Valley, British Columbia, and

SOU ESTE HINe OPI AT © sarees pea ce Maciek nce isc Ie tas coe Re nine me ee eee 43

Carcamo, H.A., J. Otani, J. Gavloski, M. Dolinski and J. Soroka. Abundance of Lygus

spp. (Heteroptera:Miridae) in canola adjacent to forage and seed alfalfa .......000000.... 55

Knight, A.L. and E. Miliczky. Influence of Trap Colour on the Capture of Codling Moth

(Lepidoptera: Tortricidae), Honeybees, and Non-target Flies .........00..0eceeeeeeeeeeees 65

Knight, A.L. Testing an attracticide hollow fibre formulation for control of Codling

Noth, Gydia pomoneila (Lepidoptera: Vorticidac)i. ihe eee eee 71

Horton, D.R. and T.M. Lewis. Numbers and types of arthropods overwintering on

common mullein, Verbascum thapsus L. (Scrophulariaceae), in a central Washington

jUGUNIETSD (en uial s[oeH Caneg (0) 0 epemnny same arenenee ne erey emacs ter see eae weet oer eee ee 79

SCIENTIFIC NOTES

Kenner, R.D., D.J. Larson and R.E. Roughley. New Aquatic Beetle Records for Canada

(Coleoptera: Haliplidae, Dytiscidae) ............cccccccccccccccccccecceessessssceeeeeeeeeseeesssssaeeeseeeeeees 89

Crozier, S., A. Tanaka and R.S. Vernon. Flight activity of Agriotes lineatus L. and A.

OusGuTuS oe (C olcoptera: Blatendae) am te dield..,...). eerste. ges ese 91

NOTICE TO CONTRIBUTORS ..0000.0.0ooccccccccceecccccceescecesesseeeeentesees Inside Back Cover

2 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

DIRECTORS OF THE ENTOMOLOGICAL SOCIETY OF BRITISH

COLUMBIA FOR 2003-4

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BC Ministry of Forests

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Royal BC Museum

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J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 3

A positive correlation between photoperiod and development rate in

summer species of Odonata could help to make emergence date

appropriate to latitude: a testable hypothesis’

PHILIP S. CORBET’

I.C.A.P.B., UNIVERSITY OF EDINBURGH,

WEST MAINS ROAD, EDINBURGH EH9 3JT, UK

ABSTRACT

In the western Nearctic and the Palaearctic Regions several species of Odonata occur,

without evident gaps in distribution, from latitude 50° N northwards to the Arctic Circle

(66°30’N) and beyond. The decline in incident solar radiation along this latitude

gradient does not appear to be reflected, as might be expected, in progressively later

emergence, despite the progress of metamorphosis being dependent on ambient

temperature. On the contrary, reports indicate that, in some species, northernmost

populations may emerge at least as early as, and sometimes even earlier than, more

southerly populations, suggesting that some mechanism exists that enables larval

developmental rate to compensate for latitude. Reported responses by late-stadium

larvae to photoperiod, placed in the context of seasonal changes of photoperiod at

different latitudes, make it plausible to postulate the existence of a single, fixed response

to photoperiod that would continuously adjust developmental rate to latitude, at least

between 50° and 70° N. In Odonata such a response, to be effective, would be confined

to species possessing a Type-2 or Type-3 life cycle, in which more than one stadium

precedes metamorphosis in spring or early summer. The hypothesis proposed here does

not invoke genetic heterogeneity of response in populations at different latitudes, such

as has been detected in certain other insects. The response predicted by the hypothesis

may complement, rather than substitute for, other mechanisms of seasonal regulation.

Steps are described by which the hypothesis could be tested in Odonata.

INTRODUCTION

Western Canada is of interest to odonatologists because it includes the highest latitudes

at which Odonata maintain populations in the Nearctic Region and because it is where

many species, commoner and better known in the United States, reach the northernmost

limits of their distribution. Some species in western Canada maintain a virtually

continuous distribution from about 50° to 70° N, 1.e. from southern British Columbia (BC)

to the Yukon and Alaska. Reports by Cannings ef a/. (1991), Cannings and Cannings

(1997) and Cannings (2002) have done much to characterize this distribution and have

provided a major impetus for this paper.

The tree line generally forms the latitudinal limit to the occurrence of resident

populations of Odonata: no species of Odonata breeds on the Arctic slope of Alaska

(Cannings ef al. 1991). In Canada the tree line occurs at progressively lower latitudes

towards the east, reaching its southernmost limit close to Churchill, Manitoba, at about

58°46’ N. This means that the 88 species of Odonata that occur in both British Columbia

' Text based on an invited, oral contribution to the Workshop “North American

Dragonflies”, included in the Joint Meeting of the Entomological Society of Canada and

the Entomological Society of Manitoba, Winnipeg, Manitoba, 9 October 2002.

* Present address: Crean Mill, St Buryan, Cornwall, TR19 6HA, United Kingdom

4 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

(BC) and the Yukon (Cannings 2002) exist as breeding populations over a wider range of

northerly latitudes than anywhere else in the Nearctic Region. Therefore I focus here on

the Odonata of western Canada, mainly northern BC and the Yukon.

Another impetus for this paper has been the clarifying research by Norling on the

seasonal regulation of those Odonata that have a wide latitudinal range in Sweden (Norling

1976, 1984a, b, c). As Norling (1984b) has remarked, species occurring over such a wide

range of latitude will be exposed to a south-north gradient characterized by progressively

shorter (and usually cooler) summers, by longer (and usually more severe) winters, and by

less predictable weather. in summer. They will also experience progressively longer

photoperiods between the spring equinox and the summer solstice (i.e. the time of most

active pre-emergence development). Such exposure implies an extreme commitment in

the northernmost species of these Odonata to early emergence, because inclement weather

during the brief northern summer can seriously erode the time available for imaginal

maturation and reproduction.

Noting the seasonal placement of the flying season of odonates along this climatic

gradient has led me to postulate a hypothetical mechanism whereby the retarding effects of

the climatic gradient might be compensated for by a unitary response to photoperiod. In

the rest of this report I explain the reasoning leading to the hypothesis and its implications:

first, I review what is known about seasonal regulation of Odonata, thus providing the

information base with which the hypothesis must be consistent; second, I formulate the

hypothesis and explore its implications for several variables; and third, I present a

protocol for testing it.

The full scientific names of all species mentioned in this account, if not in the running

text, are given in Table 1.

SEASONAL REGULATION OF ODONATA:

THE BACKGROUND

Norling (1984b) and Pritchard (1982) have placed the topic of seasonal regulation in

Odonata in broad ecological perspective. The question of seasonal adjustment according

to latitude is a subset of the more fundamental one of how a group of tropical origin such

as the Odonata has successfully colonized temperate latitudes. Pritchard (1982) concluded

that the Odonata, unlike other aquatic insect orders such as the Ephemeroptera and

Plecoptera, remain warm-adapted and have retained cold-intolerant early larval and adult

stages; so they have evolved a larval diapause that restricts the cold-intolerant stages to

the warmer times of year. This interpretation has been supported by results obtained for

several species (Norling 1984b) so that diapause in the egg and/or larva can be regarded as

a hallmark of the Odonata (among aquatic insects) that have colonised high latitudes.

Three main Types of odonate life cycle (described below) are encountered in temperate

latitudes (Corbet 1960). The first two Types, originally classified as ‘spring’ and

‘summer’ species’,respectively, have been defined by Corbet and Corbet (1958) and by

Corbet (1999). Paulson and Jenner (1971) observed that this dichotomy applies to life

cycles in high, but not necessarily low, temperate latitudes. The third Type, a subset of

summer species, comprises species that are obligatorily univoltine (completing one

generation per year). These Types refer to life cycles, not species. For example, within

one population of Anax imperator Leach a single population can exhibit two Types of life

cycle (Corbet 1957a); and populations of Coenagrion hastulatum (Charpentier) at

different latitudes can do likewise. For example, in southern Sweden at 58°42’ N, this

species 1s mainly univoltine with a Type-2 life cycle, overwintering mainly in the

penultimate larval stadium, (Norling 1984c) whereas in northern Sweden at 63°50’

(Johansson and Norling 1994) and 67°50’ N (Norling 1984c) it is mainly semivoltine

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 5

Table 1

Relative positions of flying seasons of Odonata that occur from southern BC north to the

tree line (source: Cannings 2002).

Species A B Cc D

Zygoptera

Coenagrion interrogatum (Hagen in Selys) (2) X x

C. resolutum (Hagen in Selys) (2) X x

Lestes dryas Kirby (3)

L. disjunctus Selys (3)

Enallagma boreale (Selys) (2)

E. cyathigerum Charpentier (2)

x em mK

Anisoptera

Aeshna canadensis Walker (2)

A. eremita Scudder (2) *

A. interrupta Walker (2)

A. juncea (Linnaeus) (2)

A. septentrionalis Burmeister (2) X

A. sitchensis Hagen (2) X x

A. subarctica Walker (2)

Cordulia shurtleffi Scudder (1)

Leucorrhinia borealis Hagen (1)

L. hudsonica (Selys)(1)

L. patricia Walker (1) X

~ Ke KM

~~ KM

L. proxima Calvert (1) X

Libellula quadrimaculata Linn. (1) X

Somatochlora albicincta (Burmeister) (1) X X

S. franklini (Selys) (1) Ke Ko

S. hudsonica (Hagen)(1) K X

S. kennedyi Walker (1) X

S. minor Calvert (1) Xx

S. semicircularis (Selys) (1) x

S. septentrionalis (Hagen) (1) x

Sympetrum danae (Sulzer) (3) X

S. internum Montgomery (3) X

S. madidum (Hagen) (3) X

Total species 19 9 6 1

Key to columns:

A Flying season begins earlier in south and ends later in north.

B Flying season begins at same time in south and north.

C Flying season begins at same time in north and south but ends later in south.

D Flying season begins later in south and ends at same time in north and south.

Note: The number in parentheses after each species denotes its probable, typical life-cycle

Type (see text). Where pertinent data for North America are lacking (e.g. in

Somatochlora spp.) the lifé-cycle Type for the genus has been inferred from

Palaearctic congeners.

*The only evidence available (Walker 1958) indicates that A.eremita can enter diapause in

F-0, a characteristic of the T1 life cycle.

**Unlike Cannings (2002), Walker and Corbet (1978) state that the flying season of S.

franklini is later in the north.

6 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

(completing a generation in two years), or even partivoltine (completing a generation in

more than two years), with a Type-1 life cycle. A further example of such latitude-

dependent variation is Aeshna juncea (Linnaeus), which exhibits a Type-2 life cycle in

southern Sweden but a Type-1 life cycle in northern Sweden (Norling 1984b). Aeshna

viridis Eversmann, in contrast, apparently always retains a Type-2 life cycle because its

long-day larval diapause prevents larvae from entering the final stadium (F-0) in late

summer (Norling 1971). The expression “T1 species’ will be used here as a shorthand for

‘species exhibiting a predominantly Type-1 life cycle’ and the corresponding abbreviations

will be used for the Type-2 and Type-3 life cycles.

The T1 life cycle, typified by spring species

By spending the last winter before emergence in F-0, such species can respond

promptly and synchronously to rising temperature in spring; thus they tend to emerge

early. Their eggs typically develop directly, hatching about one month or less after being

laid, although those of some Palaearctic Somatochlora are facultative in this respect,

developing directly if laid early in the summer but entering diapause if laid later (Sternberg

1995). Eggs of S. franklini, sometimes at least, enter diapause (Walker 1925). Probable

T1 examples in Canada are species of Leucorrhinia and Somatochlora, which, by analogy

with their Palaearctic congeners, are semi- or parti-voltine, having life cycles lasting more

than one year. Leucorrhinia intacta (Hagen) is known to have this Type of life cycle in

southern Ontario (Deacon 1975).

The T2 life cycle, typified by summer species

Because they spend the last winter in one or more late stadia preceding F-0, such

species typically emerge later than T1 species and with less synchronization (Corbet and

Corbet 1958). Likely examples in Canada are species of Coenagrion, Enallagma and

Aeshna which, by analogy with their Palaearctic congeners, are probably uni-, semi-, or

parti-voltine. The eggs of Aeshna species typically overwinter in diapause (for North

American species see Lincoln [1940] and Halverson [1984]). Those of Coenagrion and

Enallagma typically develop directly (for Canadian species of Coenagrion see Sawchyn

[1971] and Baker and Clifford [1981]; and for species of Enallagma see Pilon and

Masseau [1984]). Despite commencing growth in their last spring in more than one

stadium, T2 species can improve their synchronization of emergence by using a system of

rising lower temperature thresholds that enable retarded larvae to catch up with more

advanced ones (Corbet 1957b; Lutz 1968).

The T3 life cycle, typified by obligatorily univoltine species

These species represent a subset of T2. They typically, but not necessarily (see Corbet

1956a, 1999), overwinter as eggs in diapause. Larval development is completed in two or

three months in spring and early summer, and adults die in late summer. Examples from

Canada are species of Lestes (Sawchyn and Church 1973; Sawchyn and Gillott 1974;

Laplante 1975; Baker and Clifford 1981) and from North America species of Sympetrum

(Krull 1929; Tai 1967; Boehms 1971; Peterson 1975). These observations conform with

results for Palaearctic species of these genera (Corbet 1999). In several species of

Palaearctic Sympetrum and in at least one species from North America, egg diapause is

facultative (Tai 1967; Corbet 1999). Like T2 species, T3 species also, theoretically, have

available the use of rising temperature thresholds to reduce temporal variation in spring

before emergence. From experiments conducted by Krishnaraj and Pritchard (1995) on

Coenagrion resolutum and Lestes disjunctus, it is reasonable to assume that larvae of T2

and T3 species differ in their temperature coefficients for growth, the latter having the

higher coefficient as well as having a higher attack coefficient and a more flexible foraging

mode.

Some TI and T2 species, and most T3 species, have evolved cold-resistant (i.e.

diapause) eggs. In all such species, however, a relatively high temperature threshold for

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 ei

hatching after completion of diapause development ensures that the earliest larval stadia

are not exposed to low temperature in spring (for T3 species see Sawchyn and Gillott

1974; Boehms 1971; Tai 1967).

The amount of development to be completed in spring before emergence constitutes a

major difference between T1 species and the rest. T1 larvae, resuming development in

spring, especially at the highest latitudes, are ready to respond almost immediately to

rising temperature by initiating metamorphosis, in contrast to those of T2 and T3 which

still have one or more larval ecdyses to undergo before metamorphosis can begin. This

disparity alone could enable T1 species to emerge earlier at higher latitudes.

Two Episodes in the seasonal regulation of Odonata can be distinguished (Norling

1976, 1984a, b, c). These represent the manifestion of two discrete strategies that can both

act, though at different seasons, to ensure that emergence is positioned at an appropriate

time of year.

Episode 1. Retardation of larval development in late summer and early autumn so that

the larval population overwinters in an appropriate, cold-resistant stage. This process is

usually accomplished by the onset of a diapause induced by photoperiod. Initially long

(e.g. mid-summer), and perhaps sometimes decreasing, photoperiods (Norling 1984b)

postpone entry to one or more late stadia, whereupon short photoperiods prevent

development from proceeding further before the onset of winter. This Episode concerns

pre-diapause development and is well developed in the T1 life cycle in which diapause is

induced in F-0; it determines the stadium and/or intrastadial stage in which the last winter

will be passed.

Episode 2. The placement of emergence, in spring and early summer, early in the

season favourable for adult activity and survival. This Episode concerns post-diapause

development. It is achieved by responses quite different from those occurring during pre-

diapause development. In this Episode, instead of being retarded (as in Episode 1), larval

development is accelerated under long photoperiods (Norling 1984b). The larval response

to photoperiod characteristic of Episode 1 has evidently been reversed among larvae that

have experienced a period of low (winter) temperature and/or decreasing (or short)

photoperiods.

Norling (1976, 1984a, 1984b) investigated the responses of odonate larvae to

photoperiod in populations at different latitudes between 58°42’ and 68°20’ N in Sweden.

Photoperiod influences seasonal regulation in Leucorrhinia dubia (Vander Linden) (a T1

species studied by Norling) in late summer (Episode 1), when long photoperiods delay

entry to F-0 and then short photoperiods prevent any F-O larva from initiating

metamorphosis. Norling (1976) distinguished five phases of morphological development

within F-0, a stadium that had hitherto been regarded as a homogeneous developmental

stage. The photoperiodic response of each intrastadial phase differs, ensuring that larvae

entering spring in F-0 are in phase 4 which, unlike the phases preceding it, is characterized

by larvae being able to respond promptly to increasing photoperiods, by accelerating

development. The last intrastadial phase (phase 5) is brief, responsive to temperature, and

unaffected by photoperiod. This set of responses results in emergence of Leucorrhinia

dubia occurring some 7-10 days earlier than if all larvae were to remain static within F-0

and thus fail to reach phase 4 before the onset of spring.

The seasonal progression of photoperiod across the latitudinal range covered by

Norling’s work changes greatly according to latitude (Fig. 1). Norling (1984a) found that

the critical photoperiods inducing diapause in summer (Episode 1) or accelerated

development in spring (Episode 2) differed in larval populations at the extremities of this

latitudinal range. Such a phenomenon, in which discrete populations at different latitudes

differ genetically in their response to a given photoperiod, was already known from the

work by Danilevskii and his associates on Lepidoptera between 40° and 60° N in

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

(98100 “y Iq Aq (Z00Z) O[tuesep puke poor

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Jj. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 9

former Soviet Union (Danilevskii 1965, Danks 1987, Saunders 2003) and has since been

detected in a calliphorid fly with a wide latitudinal range (Saunders 2001).

This type of response, in which latitude compensation is achieved by genetic

heterogeneity of discrete populations, has been detected frequently in species exhibiting

latitude-dependent phenology. It therefore occasioned no surprise that Norling (1984a)

found such a response in Leucorrhinia dubia. However, this type of response is not what I

postulate here as a regulating factor in the seasonal ecology of boreal Odonata.

SEASONAL ECOLOGY OF BOREAL ODONATA IN CANADA

Several species (e.g. Aeshna septentrionalis (formerly Aeshna coerulea septentrionalis

Walker), Coenagrion resolutum, Lestes disjunctus, Leucorrhinia hudsonica and

Somatochlora hudsonica) occur from southern BC north to tree line (Cannings 2002).

Walker (1953) supposed that the northern limit of C. resolutum probably equated to the

northern limit of Zygoptera in general. These five species are transcontinental and mainly

boreal in distribution (Cannings 2002). In BC the southern limits of several species, as one

would expect of predominantly northern taxa, tend to be at high altitude. All these species

are widely distributed in the Yukon (Cannings et al. 1991). The demands of seasonal

regulation upon species with this pattern of distribution must severely test their powers of

adaptation and flexibility.

Progressively northern life cycles of Odonata are characterised in some species by an

increase in the time taken to complete a generation (presumably reflecting the thermal

budget and prey availability) and a narrowing of the range of stadia in which the last

winter is spent (Norling 1984b). However, because metamorphosis and emergence are

especially sensitive to low temperature, such sensitivity would seem to present a

progressive constraint along a south-north gradient characterised by declining day-degree

totals (Rae 1951; Boughner 1964). Some clues suggest that compensating mechanisms

may be operating to mitigate the effects of such a constraint For example, Walker (1943)

noted that adults of C. interrogatum appeared as early in the northern part of the species’

range as in the south and that consequently a study of the flight period throughout its range

might be rewarding. Likewise Walker (1953) noted that the flight period of Aeshna

palmata may be earlier in Alaska than in Banff. Phenological records for 29 species (six

Zygoptera and 23 Anisoptera) from nine genera (Table 1) occurring in Yukon and BC

were found (in usable form) in Walker (1953, 1958), Walker and Corbet (1978) and

Cannings (2002). Among these species, the recorded flying seasons begin earlier in the

south than the north in 19 species (Table 1, column A) and end later in the south than the

north in 26 species, a pattern conforming with expectation based solely on the thermal

gradient. Two other comparisons, however, are contrary to this expectation: in nine

species the flying season begins at about the same time in both the south and north

(column B); in six species it begins in both places at the same time but ends later in the

south (column C); and in one species (Aeshna septentrionalis) the recorded flying season

begins /ater in the south (column D). Indeed, Cannings (2002) regards A. septentrionalis

as the most boreal of Canada’s darners.

THE HYPOTHESIS

We have noted examples of insects (e.g. Lepidoptera) in which phenology is made

appropriate to latitude by discrete, regional populations exhibiting different, genetically

determined response-thresholds to photoperiod that induce or avert diapause (Danilevskii

1965). In such instances it appears that the latitude-compensation may or may not be

discontinuous. If discontinuous it can be manifest (along a latitudinal cline) by the

existence of races, each adapted to a specific region. There is, however, another, simpler

10 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

way in which a photoperiodic response might achieve the compensation for latitude which

may be occurring in western Canada.

For two reasons I accord preference here to this alternative hypothesis: first, it does not

require the assumption that the responses of populations at different latitudes differ; and

second, it postulates a single, unitary response to photoperiod that will result in seamless

compensation at all latitudes.

Many years ago (Corbet 1962), perhaps stimulated by Walker’s comment about C.

interrogatum, I theorized that a compensating mechanism might exist whereby, mediated

by a response to photoperiod, some Odonata might be able to adjust the rate of seasonal

development to latitude. Until now I have been unable to visualise the nature of such a

mechanism. My failure to do so in 1962 may have been because I was seeking an all-or-

nothing threshold response to photoperiod rather than a response manifest in a gradual

change in developmental rate.

The hypothesis I now postulate is that:

Some, perhaps many, species of Odonata possess a fixed response whereby the rate of

larval development is positively correlated with photoperiod and that, in consequence,

emergence at high latitudes occurs earlier than it would have done in the absence of such

a response.

THE EVIDENCE

In some species of insects development is accelerated under long photoperiods (the

light-growth [LG] effect), although in others long photoperiods have the opposite effect

(Saunders 2003). The LG effect is well known but apparently no one has yet suggested

that it could play a seminal role in adjusting phenology to latitude. Many species of

Odonata exhibit the LG effect (see Danks 1987; Corbet 1999). For example in late-stadium

larvae of five species of Zygoptera and the anisopteran Epitheca (formerly Tetragoneuria)

cynosura (Say) the rate of development in several late stadia is directly proportional to

photoperiod (Jenner 1958); and Dennis Procter (1973) concluded that in BC (at 49°19’°N)

an increase in (absolute) photoperiod at low temperatures can increase developmental rate

as effectively as can a temperature rise in late stadia of Enallagma boreale, Leucorrhinia

glacialis Hagen and Libellula quadrimaculata. If we allow the possibility that odonates

respond to changing, as distinct from absolute, photoperiods (see below), then we note

from Fig. 3 that the former variable, also, shows a latitude-dependent regression. This

variable, manifest as rate of change, would also provide a mechanism for enhancing rates

of development in spring in northerly populations.

The considerations above apply with particular force to T2 species and to the responses

to photoperiod of the last three or four stadia. A somewhat different case is presented by

T3 species— the obligatorily univoltine species — in which ail larval stadia are exposed to

the photoperiodic regime of spring.

A recent finding by Johansson and Rowe (1999), obtained in a different context,

provides the evidence I need to formulate a hypothesis with confidence. Johansson and

Rowe (1999), working in Guelph, Ontario (43°33’N) investigated the LG effect in Lestes

congener (Hagen), a T3 species. Their hypothesis was structured around the assumption

that, because the diapause eggs might hatch in early spring at different times, some larvae

from eggs hatching late might find themselves with insufficient time to complete

development before the season was too advanced for adults to reproduce. The authors

noted that such ‘late’ larvae, subject to a seasonal time constraint, would be completing a

given stadium later in the year and therefore under longer photoperiods than their more

advanced conspecifics. As the authors’ hypothesis predicted, larvae so placed

compensated for their backwardness by accelerating development under long

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 11

photoperiods. Later, Johansson et al. (2001) demonstrated similar responses in the

Palaearctic Lestes sponsa (Hansemann), another T3 species. Both L. congener and L.

sponsa responded to long photoperiods by completing the larval stage sooner, albeit by

producing smaller F-0 larvae. In the light of my hypothesis, these are significant findings,

even though the authors were not addressing the matter of variations in latitude. Their

results have obvious implications for a species like Lestes disjunctus which (in Canada)

occurs from southern BC north to tree line. Eggs of this species are laid in stems of

emergent plants, often above the water surface (Sawchyn and Gillott 1974) and are

therefore likely to be exposed to highly variable temperatures when they hatch in spring;

consequently larvae in different habitats are likely to start development at widely different

times, some larvae being far in advance of others. Facing the compelling need to emerge

as early as possible in the brief summer ahead, such larvae would benefit greatly from a

means of compensating for late hatching. Accordingly we may expect the LG response to

be present and well developed in populations of Lestes disjunctus also.

We have already noted that several species of Odonata respond to long photoperiods in

spring by accelerating development. Two species of Zygoptera, Coenagrion angulatum

Walker and C. resolutum, in Saskatchewan, show this response especially clearly

(Sawchyn 1971). The seasonal progression of photoperiod is such that, for the same date

in spring (after the spring equinox and before the summer solstice), the photoperiod is

longer at the more northerly latitude (Fig. 1). This means that, provided that ambient

temperature and prey availability are permissive, larvae possessing such a response to

photoperiod will develop progressively more quickly in northerly populations, to an extent

that is directly proportional to latitude. Such a (unitary) response alone would achieve the

compensatory effect needed to adjust the onset of emergence to latitude, but without the

need to invoke genetic heterogeneity between populations. When envisaging the effect of

such a compensatory response, we should note that emergence at the highest latitudes may

not necessarily be earlier than emergence at lower latitudes: the effect may only be that

emergence is earlier than it would otherwise have been without the operation of a

compensatory mechanism.

Implications of voltinism

Voltinism bears on the hypothesis, especially in regard to T2 species, in two respects.

It may correlate with the date of first emergence; and also, as a consequence of Johansson

and Rowe’s (1999) findings, with size at emergence.

Regarding the date of first emergence, we may expect the duration of larval

development of T2 species to increase with increasing latitude. Norling (1984c) found that

C. hastulatum was mainly univoltine at 58°42’ N, but that cohort-splitting occurred at a

higher latitude (67°50’N) so that the study population became semivoltine. This process

entailed the life history changing from T2 to T1 and so must have affected the date of first

emergence. Jn western Canada the taxa most likely to be subject to such a change are

species of Coenagrion and Enallagma. In Saskatchewan, at 52°15’ N, both C.

interrogatum and C. resolutum are univoltine, overwintering mainly in F-1 (Sawchyn and

Gillott 1975). C. resolutum has been found to be both uni- and semi-voltine at 51°51’ N

(Baker and Clifford 1981) and 51°5’ N (Krishmaraj and Pritchard 1995). By analogy with

C. hastulatum in Sweden, one might expect these two Canadian species of Coenagrion to

become semivoltine at the highest latitudes, but the only available evidence (Cannings and

Cannings 1997) indicates that, in the two species of Coenagrion being referred to here,

univoltinism can persist in the Yukon at least as far north as Koidern (61°58’ N) (Cannings

and Cannings 1997). If the Cannings’ (1997) observation is representative, a response to

photoperiod may be affecting development rate in early stadia also, enabling larvae to

grow more rapidly during their first summer and enabling them to overwinter in stadia late

12 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

enough to permit emergence in the next spring. If such a latitude-compensation effect

influences development rate in early stadia, it could offset the tendency for voltinism to

increase with latitude in Tl and T2 species. Then the change in voltinism with latitude

would be less pronounced in the presence of a latitude-compensating response.

Regarding size at emergence, if there were to be no change in voltinism with latitude,

one could expect F-0 larvae to be smaller at higher latitudes. However, if voltinism were

to change with latitude, this effect might be masked or even reversed. Populations of the

T2 species Enallagma cyathigerum in western Europe reveal a U-shaped relationship

between size of F-0 larvae and latitude (Johansson 2003), an effect attributed,

speculatively, by the author to the step increase in voltinism observed at about 55°N. No

such transition has yet been detected among coenagrionids in western Canada. If one

exists, this might influence predictions about a relationship between the size of F-O larvae

and latitude.

In the light of these observations, it would be interesting to determine whether

individuals from northern populations of species occupying a wide latitudinal range are

smaller than their southern counterparts. So far, I have found no indication in the literature

that this is so, except for the observations by Walker (1912) that, in Aeshna spp, an

increase in mean summer temperature correlates with an increase in the length of

abdominal segment 3 and in the length of the female anal appendages, and that in

Somatochlora franklini adults are largest at the species’ southern limit in the interior of the

continent and smallest on the Labrador coast and in the Rocky Mountains (Walker 1925).

The situation may be quite different in the Tl life cycle. Coenagrion hastulatum in

Sweden in northern populations, at 67°50’ N, when exhibiting a T1 life cycle, featured F-0

larvae that were /arger than elsewhere (Norling 1984c).

TESTING THE HYPOTHESIS

Variables to be considered

Absolute Photoperiod. To simulate photoperiod experimentally one needs to know the

lower threshold of light intensity at which a larva registers light as photoperiod. The

distributions in Figs 1 and 2 portray regimes of photoperiod at three latitudes derived from

regarding photoperiod either (in Fig.l) as the interval between sunrise and sunset,

moments when the zenith light intensity under a clear sky is about 395 lux, (Danks 1987)

or (in Fig. 2) as the interval between the beginning (before sunrise) and the end (after

sunset) of Civil Twilight, namely Crep 1 (Nielsen 1963), when the corresponding light

intensity is about 3.55 lux (Danks 1987). However, having regard to the shaded

microhabitats that odonate larvae typically occupy, the lower threshold light intensity at

which they register photoperiod is almost certainly very much less than that prevailing

under a clear sky (Nielsen 1963; Lutz and Jenner 1964; Saunders 2003; Corbet 1999).

So the light intensity above which odonate larvae register photoperiod will probably be

more closely approximated by Crep 1 than by either sunrise or sunset. Lutz and Jenner

(1964) found that the response threshold of Epitheca cynosura, whose larvae live amongst

detritus, probably lies below 0.002 lux. Accordingly, to simulate natural photoperiods,

those used in an unshaded, experimental situation should be at least as long as those

portrayed in Fig. 2.

Changing Photoperiod. To investigate responses to changing photoperiod requires so

many independent variables to be allowed for simultaneously (see Tauber et al. 1986;

Danks 1987) that such responses have very seldom been investigated rigorously. Indeed,

some lists of supposed examples (e.g. Zaslavski 1988) do not distinguish between

responses to gradual (i.e. natural) and discontinuous (unnatural or stepped) changes of

photoperiod. Attempts to demonstrate such a response in odonate larvae have been

indicative but less than conclusive (Corbet 1956b) although, from the gradual nature of

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 13

responses to photoperiod shown by Aeshna viridis Eversmann, Norling (1984b) inferred

the existence of a response to changing photoperiod. (A response to changing photoperiod

per se has, however, been rigorously demonstrated in the lacewing Chrysopa carnea

[Tauber and Tauber 1970].) The latitude-dependent change of this variable (Fig. 3)

suggests that, if odonates having an extended south-north distribution were to possess a

response to changing photoperiod, this also would provide a means of enhancing rates of

development in spring in northerly populations. Such a response might or might not act in

concert with a response to absolute photoperiod.

Sun Elevation. Because it declines with latitude, sun elevation progressively extends

the duration of twilight, as is evident by comparing values in Figs. 1 and 2. The effect of

this variable north of about 60° becomes evident in all Figures, especially Fig. 3, as the

summer solstice approaches. Fig. 3 shows that the daily increment of photoperiod changes

markedly with latitude, being about 3 and 5 min per day at latitudes 50° and 60°

respectively, and exhibiting an abrupt and disproportionate increase from an already higher

level at 70°, as the period of continuous daylight approaches. On this account, larvae

responding to increments of photoperiod will be receiving a very strong stimulus at the

highest latitudes at which Odonata exist.

Microclimate. Although air temperature is inversely proportional to latitude, the

temperature close to the ground is to some extent insulated from this trend because of the

progressive amelioration of terrestrial microclimate caused by the declining frequency of

temperature inversions, especially north of 70° N (Corbet 1969). The water temperature at

the bottom of shallow ponds benefits disproportionately from this phenomenon. In a

shallow, dark-bottomed pond at 81° N, after retreat of the permafrost, the water

temperature (both surface and bottom) remained close to 7°C, a temperature above that of

the ambient air throughout June and July (Oliver and Corbet 1966). The bottom sediment

of such ponds will benefit further by being insulated from wind-chill. These effects have

also been observed by Danks (1971), in a shallow pond at 75° N: they accentuate the

microclimatic advantage already possessed by small bodies of water which change far less

than terrestrial ones from temperate to arctic regions, the greater specific heat of water

imposing a lag that moderates seasonal and diel fluctuations (Corbet 1972). Thus animals

able to develop in shallow bodies of water are to some extent buffered against the lower air

temperature characteristic of high latitudes.

Testing Procedure

For field studies of seasonal regulation, access to habitats that are productive and

readily sampled is a prerequisite for success, a fact convincingly demonstrated in a study

of Anax junius (Drury) in southern Ontario (Trottier 1971). The survey of BC and the

Yukon (Cannings et al. 1991; Cannings and Cannings 1997) has established the location of

breeding populations of several species over a wide latitudinal range. The logistical

implications of monitoring any of these populations in a systematic way are not

insignificant but, if such a challenge can be met, exciting opportunities exist for

odonatologists wishing to test the hypothesis and thus to explore further Walker’s

enigmatic statement (1943) that northerly populations of Coenagrion interrogatum seemed

to be emerging earlier than southern ones. Appropriate, initial steps in such an

investigation might be as follows:

1) Determine the phenology of some candidate species at different latitudes. Columns B,

C and D in Table 2 provide a list of potentially suitable species. Emergence could

best be monitored by collecting exuviae or by recording the presence of teneral adults

— methods that could be used by a nonspecialist having access to a study site. The

best species to choose would be supposed T2 species having a wide latitudinal range,

14 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

e.g. Aeshna septentrionalis, Coenagrion interrogatum or C. resolutum. Preference

should be given to species in columns B, C and D of Table 1.

2) Determine the stadium composition of larvae of such T2 species embarking on

development in early spring. This information likewise could be derived from larval

samples taken by a nonspecialist able to visit a study site on chosen dates.

3) Infer the voltinism of selected species by determining the stadium composition of

larvae (if any) remaining in a water body just after emergence has finished.

4) Determine by laboratory experiment the duration of each (late) stadium, identified in

step (2), at permissive temperatures and with prey provided ad libitum, , under a range

of photoperiods, chosen because they occur naturally between the spring equinox and

the summer solstice over the latitudinal range inhabited by the species concerned. For

each species use experimental material from several populations derived from a wide

latitudinal range. When designing experiments, bear in mind that the hypothesis

predicts that in all larvae so derived the rate of development in a given stadium will

exhibit the same correlation with a given latitude. Having regard to the threshold light

intensity used by larvae to register photoperiod, recognise that photoperiods defined

by the interval between the onset of Civil Twilight at sunrise and its termination at

sunset (Fig. 2) are more likely to be appropriate for simulation in experiments than

those defined by the interval between sunrise and sunset. Attention in experiments

should be focused initially on T2 species in which several late stadia embark on

development in early spring, although, as opportunity allows, it could also be

informative to determine the LG responses of earlier stadia.

Completion of these steps would either falsify the hypothesis (in regard to absolute

photoperiod) or allow it to be sustained.

CONCLUSIONS

The foregoing review of phenological records, life-cycle Types and photoperiodic

responses of larval stadia poised for development in spring has enabled me to postulate the

hypothesis that:

Some, perhaps many, species of Odonata possess a fixed response whereby the rate of

larval development is directly correlated with photoperiod and that, in consequence,

emergence at high latitudes occurs earlier than it would have done in the absence of such

a response.

This hypothesis, which is consistent with experimental data obtained in different

contexts, helps to explain, parsimoniously, how more northerly populations of a given

species could compensate for declining incident solar radiation by using photoperiodic

responses to accelerate post-diapause development in spring. In this way such species

could emerge earlier than would have been possible had they been responding to ambient

temperature alone. To test this hypothesis could throw useful light on seasonal regulation

of northern insects.

Such an investigation might appeal to the investigator whose interests include natural

history. To tackle it would present challenges in both the field and the laboratory; and its

completion (if the hypothesis were to be sustained) would provide a secure conceptual

basis for understanding how Odonata (and other insects) in northern Canada, having

different life cycles, adjust their temperature-sensitive reproductive periods to the brief,

late-summer characteristic of the region.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 1S

Research by Norling (1976, 1984a, b, c) has revealed a complex interplay between

responses to photoperiod and temperature in the regulation of larval development of

Odonata and has shown that such responses can be modified by a larva’s past experience.

It is not suggested that the latitude-compensation hypothesis advanced here is to any extent

a substitute for the matrix of responses discovered by Norling but only that it may

complement it, enhancing its effectiveness in making the date of emergence yet more

appropriate to latitude. The array of other responses by which odonate larvae adjust their

developmental rate to season (Danks 1991) is complex and may make it less than

straightforward to isolate rigorously the compensatory response postulated in this paper.

ACKNOWLEDGEMENTS

I thank Rob Cannings, Sally Corbet, Ulf Norling and Gordon Pritchard for helpful

comments on a late draft of the manuscript; and Dr Ken George, Institute of Marine

Studies, University of Plymouth, UK for computing the data used in Fig. 3. Suggestions

from the editor and two anonymous reviewers greatly improved the presentation of the

manuscript.

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Distribution and life cycle of Rhyacionia buoliana

(Lepidoptera: Tortricidae) in the interior of

British Columbia

TIA HEELEY, RENE I.ALFARO’, LELAND HUMBLE

PACIFIC FORESTRY CENTRE, CANADIAN FOREST SERVICE,

506 WEST BURNSIDE ROAD, VICTORIA, BRITISH COLUMBIA, CANADA V8Z 1M5

WARD STRONG

BRITISH COLUMBIA MINISTRY OF FORESTS, KALAMALKA FORESTRY CENTRE,

3401 RESERVOIR ROAD, VERNON, BRITISH COLUMBIA, CANADA VIB 2C7

ABSTRACT

The European pine shoot moth, Rhyacionia buoliana (Denis and Schiffermueller), is an

exotic shoot-boring insect of hard pines in British Columbia. In 1999 infestations of

this pest in native lodgepole pine were reported at a seed orchard in the interior of this

province where large numbers of the shoot moth reduced seed production by damaging

pollen and cone bearing shoots. Rhyacionia buoliana were recorded on about 80% of

the trees in a lodgepole pine seed orchard in June 2000. Pheromone trap catches and

weather observations over three years indicated that first, and peak R. buoliana flight

occurred when approximately 1000, and 1680 degree-days, respectively had

accumulated from January to August (using a threshold of —2.2 °C). We found no

evidence of a serious threat to natural lodgepole pine stands from R. buoliana damage.

Head capsule measurements confirmed the presence of six larval instars in R. buoliana

in BC.

INTRODUCTION

The European pine shoot moth, Rhyacionia buoliana (Denis and Schiffermueller), is an

important shoot-boring insect of hard pines in Canada (Syme ef a/. 1995). In the west,

lodgepole pine Pinus contorta (Douglas) is the most affected native species, while it is

most often found on ornamentals such as mugho pine, Pinus mugo (Terra). It was first

discovered in North America in 1914 on Long Island, New York, on imported ornamental

pines from Europe (Busck 1914; Green 1962; Martineau 1984). This moth was first

recorded in British Columbia (BC), in Victoria, on imported nursery stock in 1925 (Ferris

1996). The first recorded outbreak on the mainland of BC occurred in 1938 when native

lodgepole pine planted as ornamentals in Vancouver were attacked (Mathers 1938). By

1961 the moth had spread to the interior of BC (Harris and Wood 1967; Evans 1973).

Presently the host range in the Pacific Northwest of North America extends from north of

Kamloops, BC (50° 41' 40 N, 120° 27' W) south near Salem, Oregon (45° 31' N, 122° 41'

W).

Rhyacionia buoliana has one generation per year in BC. Adult moths have light reddish

orange and silver forewings, gray hind wings, and a wing span of approximately 19 mm.

Adults emerge in late spring and early summer. Within 24 h of emergence they mate and

begin to lay eggs (Ferris 1996). Eggs are laid on shoots during June and July, on or near

the buds of the lower branches of host trees. Hatching occurs approximately two wk later;

' Corresponding author. ralfaro@pfc.forestry.ca

20 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

first- and second-instar larvae construct tunnel-like webs, coated with resin and debris,

between needle bases and elongating shoots of the current year’s growth (Syme et al.

1995). Initial feeding occurs on needles within these webs (Ferris 1996). Third-instar

larvae exit these webs, migrate to new buds, and construct larger, resin-lined webs between

buds. Larvae then bore into, feed upon and kill these buds before overwintering there

(Martineau 1984). The following spring, larvae migrate to the upper branches and bore

into and deform or kill elongating shoots. Here they complete the final three larval instars

before pupating for about two wk (Martineau 1984).

Rhyacionia buoliana damage results in deformities such as forked or crooked stems,

bushy growth, multiple tops (Harris and Wood 1967; Alvarez de Araya and Ramirez 1989;

Ferris 1996), and, in commercially harvested species, lowered timber quality (Miller et al.

1961). Thus far, R. buoliana has not been considered an important forest pest in Canada,

except for attacks on forest nursery seedlings; incidence on lodgepole pine in forestry

settings is minimal.

However, in recent years significant damage has occurred in a lodgepole pine seed

orchard in the Okanagan Valley of south central BC. In 1999, larvae of R. buoliana were

detected in at least one shoot per tree in 25% of lodgepole pines at the Vernon Seed

Orchard Company near Vernon, BC (50° 23' N, 119°33' W) (Tim Lee pers. comm. Vernon

Seed Orchard, Vernon BC). This site includes 10,739 grafted lodgepole pine trees in three

orchards, representing pines from three different areas in British Columbia: Bulkley

Valley, Willow-Bowron and the Central Plateau. Due to grafting, trees vary in age from 70

to 90 y and height of 1 to6m. In 2000, the infestation increased to approximately 80% of

the lodgepole pine trees. In response, orchard managers instituted a program of chemical

and mechanical control in 2000 and 2001, and chemical control alone in 2002 (Tim Lee

pers. comm. Vernon Seed Orchard, Vernon BC). Chemical control with a systemic spray

was used in mid-July to target feeding larvae. Mechanical control consisted of clipping

and removing infested shoots by hand, before R. buoliana adults had emerged.

Our objectives were to study R. buoliana in the south central interior of BC and

determine: a) its current distribution using pheromone-baited traps, b) male flight activity

in relation to degree-day accumulation, and c) larval development period.

MATERIALS AND METHODS

Rhyacionia buoliana distribution and flight period. Pherocon I] Diamond Traps©

(Pherocon Ltd, Adair , Oklahoma) containing a Pherotech© (Pherotech Ltd, Richmond,

BC Canada) flex pheromone lure with 20 ug of 97:3 E-9-dodecenyl : E-9-dodecenol

(Gray et al. 1984) were placed in areas of high lodgepole pine density in the south central

interior of BC (Fig. 1) in the summers of 2001 and 2002. In 2001, 86 of the 134 traps were

hung in lodgepole pine at the Vernon Seed Orchard Company, thought to be the center of

the infestation. The average orchard size is 119 by 237 m. Traps were placed in 60 x 54 m

spacing at a height of 1 to 2 m, close to the stem, on the northeast side for protection

against the direct sun. The remaining 48 traps were placed on ornamental and native pines,

primarily mugho, lodgepole and ponderosa pines, in urban and rural settings around

Kelowna and Vernon. In urban areas traps were placed on mugho pine, in outlying rural

areas On ponderosa pine and at higher elevations and the Vernon seed orchard, lodgepole

pine. Traps were placed in trees in early May before moth flight had begun, and removed

after moth counts remained zero for more than two wk. Traps were checked and cleaned

twice a week; pheromone flex lures did not require changing during the study period. In

2002, the trapping program was expanded south to Osoyoos and north to Kamloops and

Salmon Arm (Fig. 1). Traps were placed on accessible pine trees.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 ZA

Silver Star

Mountain

Kalamalka

Lake

Lf oe Edward

Okanagan S :

lake + a Main

British

Columbia

Figure 1. Location of pheromone traps used to monitor the distribution of Rhyacionia

buoliana in the south central interior of British Columbia in 2002. Numbers with arrows

attached to circles indicate number of moths caught in a group of traps. The dark gray

circles indicate trap captures of more than five moths.

The 2001 and 2002 catches and flight duration at the Vernon Seed Orchard Company

were compared to catch data in 2000 (data provided by CropHealth Advising and

Research, Kelowna BC). Multiple years were compared to determine the repeatability of

adult male captures in pheromone traps in relation to degree-days.

Degree-day accumulation. Daily minimum and maximum temperature data from

Environment Canada were used to calculate degree-day accumulation from 1 January to 31

August, 2000 to 2002 using data from the Vernon/Coldstream weather station, located

approximately 6 km east of the seed orchard. Regan et a/. (1991) concluded that the most

reliable degree-day calculations for development of R. buoliana larvae in Oregon, USA,

were obtained using a minimum threshold temperature of —2.2 °C. Therefore we used this

temperature and the sine method outlined by Raworth (1994) for degree-day calculations.

Based on trap catches we calculated the degree-day accumulation to initial and peak flight

and to various percent levels of trapped males. For 2000, pheromone trap data collected by

CropHealth Advising and Research were used. ;

Larval development. The number and moult timing of R. buoliana instars were

determined through larval head capsule measurements. From 27 April through 12 June

2002 fifty infested pine shoots were collected at two-wk intervals from the Vernon area

22 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

and dissected to extract and measure R. buoliana larvae. On 12 August 2002, samples of

shoots were collected in order to obtain third-instar larvae. Larvae were preserved in glass

jars with 70% ethanol. Subsequently, larval head capsule widths were measured using

SigmaPro Scan© software to an accuracy of +0.01 mm. Voucher specimens of larvae and

adult moths were deposited in the Insectary at the Pacific Forestry Centre, Victoria BC

(PFC).

RESULTS

Rhyacionia buoliana distribution. Rhyacionia buoliana was detected in the western

portion of the Vernon Forest District, and concentrated in the urban centers of Penticton,

Kelowna, and Vernon areas (Fig. 1). Low populations were found in the Kamloops,

Salmon Arm and Oliver urban areas. Higher elevation, natural lodgepole pine stands, such

as the Rob Roy Forest Service road and King Edward main locations, yielded no evidence

of R. buoliana. Moth populations were found to be higher in urban than in suburban

areas, perhaps due to higher concentrations of ornamental pines which offer a more readily

available source of food for larvae. The absence of trapped adults in high-elevation pine

forests may be due to the fact that the natural stands sampled are older than the urban trees

or orchard trees, and therefore, have shoots of different foliage quality. In addition, it is

possible that the absence of populations in natural lodgepole stands may be due to the fact

that these stands occur at high elevations, where winter temperatures often fall below the

R. buoliana survival threshold of —22 °C (Green 1962). In 2001, two adult males were

caught in two traps in outlying rural areas of Kelowna and Vernon where no exotic

ornamental pines appear to occur within less than five km. This suggests the presence of

R. buoliana in wild lodgepole pine stands. However, a comprehensive trapping in wild

lodgepole pine is necessary to confirm this point.

Degree-day accumulation and flight period. Flight period of adult male R. buoliana

in the Okanagan Valley and neighbouring areas began in mid-June and ended in the third

week of July. In all study years moths began to appear in traps between Julian dates 157

and 165, or after the accumulation of approximately 1000 degree-days. Table 1 indicates

degree-day accumulations required to obtain various percent levels of male captures in the

south central interior of BC. Fifty percent of the total catch occurred after accumulation of

1958, 1545, and 1507 degree-days in 2000, 2001, and 2002 respectively (mean value =

1670) (Table 1). These results are comparable to values obtained by Regan et al. (1991) in

Oregon. A quadratic curve fitted to the moth catch data for 2000, 2001, 2002 (Fig. 2)

estimated that, the beginning of moth captures and peak flight occur when approximately

1000 and 1680 degree-days above —2.2 °C, respectively, have accumulated from 1 January.

Table 1.

Number of degree-days accumulated above a threshold of —2.2 °C from 1 January for

different percentages of Rhyacionia buoliana adult males caught at the Vernon Seed

Orchard Company, Vernon BC

10% 20% 50% 90%

Julian Julian Julian Julian

Year Date Degree Day Date Degree Day Date Degree Day Date Degree Day

2000 174 1515.99 181 1680.99 195 1957.79 195 1957.79

2001 157 1166.34 172 1418.84 We) 1544.54 198 1877.66

2002 168 1330.85 170 1366.20 176 1507.27 183 1649.67

Mean 166 1337.73 174 1488.68 183 1669.87 190 1828.37

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 23

i<e)

j=)

fos)

TRAP CATCHES (No. male moths)

Oo YEAR=2000

O YEAR=2001

; eee eee

800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 ° YEAR=2002

DEGREE DAYS ABOVE -2.2 °C SINCE 1 JANUARY

Figure 2. Degree-day accumulation (—2.2 °C threshold, 1 Jan start date) at the Vernon

Seed Orchard Company for adult Rhyacionia buoliana catches in pheromone traps for

three years (2000 — 2002). Solid curve represents fitted quadratic regression; dotted lines

are the 95% confidence limits for the curve. Arrow indicates degree-days to peak

emergence (y = -7.94 * 10°x* + 0.268x - 190, F = 8.91, df = 2, 31, R° = 0.365 and P <

0.0008)

No of observations

No. of observation

0 kK ee

03 04 05 06 07 08 rr 10 1 1 13°14 15

Head Capsule Width (mm)

mean = 0.71 mm

No. of observations

0 :

03°04 05 06 07 08 “i Ml ide — 13°14 15

Head Capsule Width (mm)

No of observations

No. of observations

03 04 OS O06 O7 08 O09 10 11 #12 #13 14 «15

Head Capsule Width (mm) Head Gas Width (mm)

Figure 3. Rhyacionia buoliana head capsule widths and instar stages (Vernon BC area,

2002). Graphs arranged according to head capsule width sizes, rather than in chronological

order, to depict clearly the different instar head capsule sizes. A bar represents the sum of

all points in the interval. Mean head capsule widths (mm) for each instar according to

Pointing (1963) are I= 0.28, IT = 0.37, II = 0.55, IV = 0.64, V = 0.90, VI = 1.23.

24 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Larval development. Comparing our head capsule measurement data to established

head capsule size classes (Pointing 1963), we confirmed the presence of four of the six

larval instars (III to VI) in the south central interior of BC (Fig. 3) as identified for R.

buoliana in Ontario (Pointing 1963). The sampling period utilized in our study did not

allow us to identify instars I and II. Head capsule measurements of larval samples collected

on 12 August indicated a mean width of 0.50 mm, which according to Pointing (1963)

corresponds to instar III (Fig. 3). Between May and June there were three instars, IV, V,

and VI. The head capsule widths for instar III show a clearly defined single peak (Fig. 3).

However, the frequency distribution for samples collected at all other dates exhibited a

greater range of variability than instar III. This increased range in head capsule size may

be attributable to larval females being larger than males; larval females may outnumber

males three to one (Pointing 1963), which may result in wider head capsule distributions.

Earlier instars would not have such a distribution because male and female larvae are

similar in morphology.

In summary, our observations indicate that in south central BC, moth flight occurs

between mid-June (Julian date 166, Table 1) and mid-July (Julian date 190, Table 1).

Instars I to III occur between late July to mid-August (Fig 3). Following overwintering,

instar IV can be observed in late April and instars V and VI occur between early May and

mid-June. Also observations conducted in 2000 to 2002 indicate that pupation begins at the

end of May and continues until early July.

DISCUSSION

Economic losses attributable to R. buoliana in seed orchards have not been documented

in the literature, but we believe that prolonged infestations can result in economic loss due

to reduced seed production and increased costs of chemical and mechanical control in

order to manage this pest. Moth distribution within the western portion of the Vernon

Forest District indicates the potential for an increase in shoot moth population in the

Okanagan Valley. However, the winter temperatures at high elevations may limit the

range at which the shoot moth can survive (Green 1962). This may account for the

absence of trap catches in natural lodgepole stands, that largely occur at high elevations,

such as up the Rob Roy Forest Service road, west of Falkland (Fig. 1). Since R. buoliana

is likely to continue to damage lodegpole pine trees at the Vernon Seed Orchard Company

and may affect other sites, we recommend that surveys be conducted on other lodgepole

pine seed orchards in the area, as well as in neighbouring natural and planted pine

plantations, including Christmas tree plantations.

The information on lifecycle, periods of larval activity, and degree-day accumulation

presented here can be incorporated into a management plan for effective monitoring and

control of R. buoliana populations. Pheromone traps should be in place prior to the

accumulation of 1000 degree-days above —2.2 °C (i.e. before first flight). Chemical control

using systemic insecticides, if needed, should target sixth-instar larvae in late May to early

June (accumulation of 973 degree-days). First-instar larvae migrating to new buds about

two weeks after peak adult flight period (1680 degree-days) may also be vulnerable to

systemic chemical control.

The R. buoliana infestation at the Vernon Seed Orchard Company might be attributed

to superior tree stock, grown under optimal conditions, providing well-developed needles

and buds, which make the trees more susceptible to attack. This abundant supply of

susceptible food may have been a factor in the shoot moth host shift from ornamentals to

this lodgepole pine seed orchard.

When R. buoliana was first discovered on nursery stock in BC, the likelihood of its

spread to native pine plantations was considered by both the Canadian and US Forest

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 29

Service’s (Harris and Wood 1967, Howard 1963). After noting that attacks concentrated

mostly on ornamentals and did not pose a threat to native pine plantations, interest in this

insect decreased. However, with increased planting of genetically improved, fast-growing

lodgepole pine, the increased reliance on site amelioration, and the potential for climate

change to create a favorable environment, the ability of this exotic insect to increase its

range and cause serious economic damage in forestry settings must be considered.

ACKNOWLEDGEMENTS

This work was financed by the Ministry of Forests Operational Tree Improvement Plan

grant no. SPU1006 to René I. Alfaro. We thank Mario Lanthier of CropHealth Advising

and Research for generously providing the 2000 trap catch numbers and for field

assistance, Tom Gray for offering his invaluable advice and expertise, Lara Van Akker for

field assistance, Bob Duncan and Jane Seed for insect identifications, and Tim Lee and

Dan Gaudet from the Vernon Seed Orchard for their cooperation in the project.

REFERENCES

Alvarez de Araya, G and O. Ramirez. 1989. Assessment of damage caused by European pine shoot moth in

radiata pine plantations in Chile, pp. 145-154. Jn R.I. Alfaro, and S.G. Glover (Eds), Insects affecting

reforestation: biology and damage. Forestry Canada, Pacific Forestry Center, Victoria, Canada.

Busck, A. 1914. A destructive pine moth introduced from Europe. Journal of Economic Entomology 7:

340-341.

Evans, D. 1973. Establishment and survival of European pine shoot moth on container-grown 1-0

lodgepole pine. Canadian Forestry Service Pacific Forestry Research Center Information Report BC-

X-79, Victoria, Canada.

Ferris, R.L. 1996. European pine shoot moth. Canadian Forestry Service Pacific Forestry Center. Forest

Pest Leaflet 18, Victoria, BC.

Gray, T.G., K.N. Slessor, R.F. Shepherd, G.G. Grant, and J.F. Manville 1984. European pine shoot moth,

Rhyacionia buoliana (Lepidoptera: Tortricidae): Identification of additional pheromone components

resulting in an improved lure. The Canadian Entomologist 116: 1525-1532.

Green, G.W. 1962. Low winter temperatures and the European pine shoot moth, Rhyacionia buoliana

(Schiff.), in Ontario. The Canadian Entomologist 94: 314-337.

Harris, J.W.E., and R. O. Wood. 1967. The European pine shoot moth, Rhyacionia buoliana (Lepidoptera:

Olethreutidae), another introduced forest pest. Journal of the Entomological Society of BC 64:14-16.

Howard, B. 1963. The European pine shoot moth program in the Northwest 1959 — 1963. U.S forest

Service, Pacific Northwest Region. Portland, Oregon.

Martineau, R. 1984. Insects harmful to forest trees. Forest Technology Report 32, Canadian Forestry

Service, Ottawa, Canada.

Mathers, W.G. 1938. Annual Report of the Vancouver Forest Insect Lab. Canadian Department of

Agriculture, Ottawa, Canada.

Miller, W.E., A.R. Hastings, and J.F. Wootten. 1961. European pine shoot moth. Forest Insect and Disease

Leaflet 59. USDA Forest Service. Government printing office, Columbus, Ohio.

Pointing, P.J. 1963. The biology and behavior of the European pine shoot moth, RAyacionia buoliana

(Shiff.), in southern Ontario II. Egg, larva, and pupa. The Canadian Entomologist 95: 844-62.

Raworth, D.A. 1994. Estimation of degree-days using temperature data recorded at regular intervals.

Environmental Entomology 23: 893-98.

Regan, R.P., J.D. De Angelis, and G. Gredler. 1991. Predicting Seasonal Flight of European Pine Shoot

Moth (Lepidoptera: Tortricidae) in Western Oregon. Environmental Entomology 20: 1403-1406.

Syme, P.D., G.G. Grant, and T.G. Gray. 1995. European pine shoot moth, Rhyacionia buoliana, and other

Olethreutid shoot borers and tip moths, pp. 271-277. Jn J.A. Armstrong and W.G.H. Ives (Eds), Forest

Insect Pests in Canada. Natural Resources Canada, Canadian Forest Service, Ottawa, Canada.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 20

Impact of the western balsam bark beetle, Dryocoetes

confusus Swaine (Coleoptera: Scolytidae), at the Sicamous

Creek research site, and the potential for semiochemical

based management in alternative silviculture systems

LORRAINE E. MACLAUCHLAN!

B.C. MINISTRY OF FORESTS, SOUTHERN INTERIOR REGION,

515 COLUMBIA STREET, KAMLOOPS, B.C. V2C 2T7

LEROY HARDER

23392-16'# AVENUE, LANGLEY, B.C. V2Z 1K7

JOHN H. BORDEN

PHERO TECH INC., 7572 PROGRESS WAY, R.R. #5, DELTA, B.C. V4G 1E9

JULIE E. BROOKS

FOREST HEALTH MANAGEMENT, BOX 19, GRANTHAMS LANDING, B.C. VON 1X0

ABSTRACT

Two pre-harvest baiting regimes were tested for their effect on Dryocoetes confusus in

select stands at the Sicamous Creek Silviculture Systems Project. Single tree and two-

tree bait treatments, in addition to a control area, were established in a grid format

throughout the research area. There were significantly more new D. confusus attacks in

the baited areas than in the control area. Eighty percent of mass attacks occurred within

9 m of single tree bait centres, while 75% of mass attacks occurred within 10 m of two-

tree bait centres. Baiting appears to concentrate attacks into a discrete area and

therefore could be used in single tree selection or patch cut systems (cuts generally less

than 5 ha in size), two of the silviculture systems applied at the Sicamous Creek

research area. Of 136 dead subalpine fir trees felled and examined, 105 (77%) showed

clear evidence of D. confusus attack, making it the major cause of sub-alpine fir

mortality at the Sicamous Creek research site. Naturally attacked trees had more

advanced brood development and beetles utilized a greater percent of the total tree bole

but had lower attack density (number of D. confusus galleries per unit area) than was

observed on baited trees. In baited trees, the higher attack density resulted in indistinct

gallery systems due to space competition of the brood. This suggested that there was a

limited acceptable area for attack in these trees, which would not normally be

susceptible. This study concludes it is possible to reduce resident populations of D.

confusus by varying the number and placement of bait trees as a pre-harvest treatment.

Key words: Dryocoetes confusus, western balsam bark beetle, pheromone baiting,

Abies lasiocarpa, subalpine fir

' Author to whom all correspondence should be sent.

28 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

INTRODUCTION

The western balsam bark beetle, Dryocoetes confusus Swaine (Coleoptera: Scolytidae),

is the most destructive insect pest of subalpine fir, Abies lasiocarpa (Hook.) Nutt., in

British Columbia (Garbutt 1992; McMillin et a/. 2001). Subalpine fir is also susceptible to

a variety of other disturbance agents, including other insects, root and butt rots, stem rots

and windthrow (Kneeshaw and Burton 1997). Cumulative mortality due to D. confusus

may reach significant levels in chronically infested stands (Garbutt and Stewart 1991),

however D. confusus outbreak dynamics appear to be very different from other tree-killing

bark beetles. Over time, aerial overview surveys have established an average annual loss

of 4.2 m’ per hectare in older affected stands. D. confusus can kill many trees in a single

year but usually less than 5% of any given stand is attacked in one year (Garbutt 1992).

Beetle populations can persist for many years in a stand slowly killing the entire mature

and semi-mature component of sub-alpine fir (Garbutt 1992).

Subalpine fir comprises 12% of total timber volume (trees cut) in B.C. (B.C. Ministry

of Forests 1993) and has typically been harvested in conjunction with higher valued

spruce. As low elevation stands consisting of other tree species are depleted, the number

of subalpine fir sites harvested has increased. In 1990, (B.C. Ministry of Forests 1992)

subalpine fir comprised 8% of total volume harvested in the interior of B.C. compared to

10.9% volume in 2000-01 (B.C. Ministry of Forests 2001). As harvesting increases in

subalpine fir sites, additional research is needed to develop more effective and ecologically

sensitive management strategies.

In 1990, the B.C. Ministry of Forests established a silviculture systems project at

Sicamous Creek near Salmon Arm, B.C., to address ecosystem responses to a wide range

of disturbance levels created by harvesting. The Sicamous Creek site is located within the

Engelmann Spruce- Subalpine Fir wet, cold subzone (ESSFwc2) (Lloyd et al., 1990),

which is the largest of the seven ESSF subzones in the Kamloops Forest Region. This

study was established at the Sicamous Creek research site to test how two baiting

techniques could be used to manage D. confusus under different harvesting regimes.

Baiting trees with semiochemicals as a pre-harvest containment and concentration

tactic is a well established pest management methodology for other bark beetles such as

the mountain pine beetle, Dendroctonus ponderosae Hopkins, (Borden 1990; Maclauchlan

and Brooks 1999) but has not been developed for D. confusus. Therefore, a trial was

developed to test baiting systems that could be used in a single tree selection and patch

cutting harvest scenarios.

Our objectives were to: assess past infestations of D. confusus at the Sicamous Creek

Silviculture Systems Project; test the efficacy of pre-harvest baiting systems for D.

confusus in different silviculture systems; and determine if pre-harvest baiting could

concentrate more beetles for removal at harvest than no baiting.

METHODS

Pre- and post-harvest levels of D. confusus

The Sicamous Creek research site 1s dominated by subalpine fir and Engelmann spruce

(Picea engelmanni Parry ex Engelm.). The harvest regimes, each on 30 ha, were: 1)

control/no removal; 2) single tree selection in which 33% of the volume was removed over

a 30 ha area by cutting every fifth tree using faller’s choice; 3) 0.1 ha patch cuts; 4) 1 ha

patch cuts; and, 5) 10 ha clearcut. Each of the harvest regimes removed 33% of the

volume. The area was harvested without taking into account the presence or impact of D.

confusus, even though there was significant mortality throughout the area.

Aerial photographs (1:5,000) of the Sicamous Creek silviculture systems project for the

years 1993-1995 were used to map the location of red trees over a 200 ha area. Using

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 22

1993 photographs, groups of red trees were identified and mapped on an acetate overlay.

For 1994, groups of red trees adjacent to the original clusters were identified and mapped.

Each cluster was coded in relation to the eventual harvest regime conducted in the winter

of 1994-1995. The red trees mapped from the 1995 photographs were used to compare the

relative efficacy of the five cutting regimes in removing D. confusus. The uncut strips of

trees between the 0.1 ha and 1.0 ha patch cuts were located on the photographs and

assessed for red trees.

Infestation characteristics

Prior to adult emergence in the spring of 1995, 15 red, 31 grey and 90 older snags,

were felled and examined for evidence of D. confusus activity. The following

characteristics were measured or noted in the red and grey trees: diameter at breast height

(d.b.h.) of the bole and distance from the ground for upper and lower limits of attack;

resinosis typical of D. confusus attack; exit holes; and the presence of live adults, pupae

and larvae. Because snags were usually quite degraded, only the presence or absence of D.

confusus galleries, exit holes and associated resinosis were recorded and measured in those

trees.

Pheromone baiting trial

In June 1995, a baiting trial was established at Sicamous Creek. Two treatments and a

control area were laid out. The aggregation pheromone (+)-exo-brevicomin (released at 0.3

mg/24 hrs release rate) was used (Phero Tech Inc.). Baits were stapled at 1.5 m on the

north side of large subalpine fir. In the single tree bait treatment, established in the single

tree selection area, bait lines were 50 m apart, with baited trees at 25 m intervals in a grid

pattern. In the two-tree bait treatment, established in the 0.1 ha patch cut area, bait lines

were placed 33 m apart, with baits affixed every 66 m along the bait line, on two adjacent,

large subalpine firs at each point. Baits on adjacent lines were offset by 33 m. In total, 86

single and 82 paired trees were baited. No baits were used in the control area. A chi

Square analysis was used to compare the number of green (live) trees to red (attacked) trees

in the three treatment regimes.

In September 1995, a 100% ground assessment of all subalpine fir in the three study

areas was conducted. Using Stock’s (1991) criteria for “attack classes” in Table 1 a stem

map was produced of the baited, attacked, mass attacked, red and grey trees. The d.b.h. of

these trees was measured, and the number of snags in each area was counted. In each

treatment, 10 randomly placed 15 m radius circular plots were established, to discern

infestation characteristics. In each circular plot the d.b.h., species and tree class were

recorded for each tree with minimum 9 cm d.b.h. Chi square analysis was used to compare

the d.b.h. frequency distribution of red, grey and snags to unattacked trees.

Comparison of insect development on baited and naturally attacked subalpine fir

In late August 1996, 10 baited mass attacked trees in the single tree bait treatment area

and 13 new mass attacked trees outside the study area were felled. Beginning at the stump

(cut end of tree), gallery systems were dissected in 1030 cm bark sections every 1.5 m

along the bole. For each sample, the number of gallery systems and the occurrence of

associated species were recorded. Within each gallery system, the presence or absence of

D. confusus life stages and resin was recorded, and the length of each egg gallery was

measured. Female D. confusus constructs the egg gallery away from the nuptial chamber

where she mates and deposits eggs along the sides of these galleries. The upper bole of the

tree was examined for secondary scolytids and other associated insects. These scolytids

are often referred to as secondary bark beetles as they do not typically kill trees but occupy

trees infested by other tree killing species of the Scolytidae. Height limits for conspicuous

resin flow was also noted. Foliage colour change was rated using a six point rating system

(Table 2).

30 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Table 1

Tree classifications assigned to subalpine firs attacked by D. confusus. These “Attack

Classes” were developed by Stock (1991) and modified by L. Harder.

Attack Class Description

attacked streams of resin on bole (presumed unsuccessfully attacked)

mass attacked _frass and possibly resin on bole (presumed successful intense

colonization of tree)

red red foliage present (represents old attack from which new mature

beetles emerge)

grey needles mostly gone, but fine twigs present and bark generally intact

(no beetles remaining in bark)

snag a long dead tree; minimum height 2 m and d.b.h. 12 cm, with bark

loose or absent and fine twigs gone

Table 2

Foliage colour classes used to classify colour changes in subalpine fir trees one year after

mass attack by D. confusus.

Colour Class Description

0 No colour change noticeable

1 Red needles on some tree limbs, usually on lower bole

Foliage on less than '4 of the tree limbs starting to turn red, usually on

lower bole

Half the foliage turned red

Most of the foliage turned red, some faded green left

Foliage completely red

Mm BW NN

Baited and naturally mass attacked trees were compared using a chi square test based

on the number of trees containing different life stages of young brood. Samples without

gallery systems, and gallery systems without brood, were classed as failed gallery systems

and compared to other characteristics of attack by using a chi square test. Analysis of

variance comparing naturally attacked trees and baited trees were done on gallery length,

resin flow, number of egg galleries, and the total brood gallery length.

RESULTS AND DISCUSSION

Pre- and post-harvest levels of D. confusus

The mapped number of red trees decreased from 1993 to 1995 in both undisturbed and

harvested areas (Table 3) indicating an overall decline in the Dryocoetes population.

Because clearcut treatments (1 ha and 10 ha) remove all trees in an area, all D. confusus

attacks were also removed in the harvested areas. Fewer red trees were observed in the 0.1

ha and single tree selection cut areas than in the 1.0 ha patch cut area (Table 3). The buffer

strips between the 1.0 ha patch cuts were undisturbed by harvesting therefore, there was a

similar level of attack there as in the undisturbed control areas. In the other two

treatments, the 0.1 ha patch cut plus buffer strip and the single tree selection, there was so

little area between the cuts that more attacked trees were removed at the time of harvest.

Any dead trees within the narrow buffer strips, many of which were infested with

Dryocoetes, were removed at the time of harvest. Thus, despite the lack of a conscious

effort to manage for Dryocoetes, much of the resident beetle population was removed from

these areas when harvested.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 3]

Table 3

Numbers of red subalpine fir per hectare in undisturbed and treated areas before and after

treatment as seen in three consecutive years of aerial photographs.

No. red trees per ha

Sample pre-treatment post-treatment

Location of red trees Size(ha) 1993 1994° 1995

Undisturbed control area 108 74 G2 4.5

Within 10 ha clearcut 10 50 7.9 0

Within 1.0 ha patch cuts 9 10.1 oo 0

In buffer strip between 1.0 ha 30 8.6 7.8 4.5

patch cut

In 0.1 ha patch cut and buffer 18 5) 8.9 13

strip

In single tree selection area 21 4.0 3.6 0.7

* Road right-of-way cut through research area in 1994.

Table 4

Evidence of past attack by D. confusus in felled red, grey and snag subalpine fir. The

characteristics assessed included D. confusus brood (eggs, larvae, pupae), adult beetles,

galleries, exit holes made by emerging beetles and resin flow on the bole of the tree caused

by attacking beetles. The number of trees having all of the above-mentioned

characteristics was also summarized.

% subalpine fir with characteristic

Characteristic assessed Red (n=15) Grey (n=31) Snag (n=90)*

D. confusus brood 27 3 0

D. confusus adults L3 3 0

Galleries 100 90 70

Exit holes 80 87 63

Resin flow : 93 94 56

Characteristics combined 100 97 76

* Fewer snags were assessed for exit holes (n=87) and resin flow (n=72) than for other

characteristics due to deterioration and loss of bark.

Infestation characteristics

All 15 felled red trees and 30 of 31 grey trees showed evidence of past attack by D.

confusus (Table 4). Twelve of 15 red trees had exit holes, while only 4 of 15 had juvenile

life stages, and two had adults. There was less evidence of beetle attack in snags due to

deterioration and loss of bark. This is strong evidence that most of the dead subalpine fir

in the study area had been attacked by D. confusus.

Attacked subalpine fir can retain their red foliage for a number of years prior to

shedding needles and being termed grey. The examination of red and grey trees revealed

that few D. confusus adults were still present (Table 4), suggesting that adult beetles leave

red trees before trees become grey.

Successful completion of development by D. confusus occurred primarily along the

lower portion of the bole. In general, exit holes occurred within the upper and lower limits

of the gallery systems (Figures 1, 2). In 32 trees that had visible resinosis, resin flow

usually overlapped the exit hole zone and in 28 trees, extended above the exit holes a few

metres. There was less variation in the lower height limit for gallery systems and exit

32 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

holes than in the upper height limit. Exit holes associated with other beetles in the Family

Scolytidae occurred throughout the resin flow zone extending past it in both directions.

Secondary scolytids found in the lower bole were identified as Pityokteines minutus, and

those in the upper bole as Pityophthorus sp.

The narrow variance in height of the lower limit of D. confusus galleries and exit holes,

and the broader variance in diameter (Figure 2) suggest that height was of greater

importance than diameter in limiting D. confusus occupation at the lower end of the bole.

Poor gallery development between 1 and 2 m may be related to cooler nighttime summer

temperatures close to the ground, typical in the ESSF (Farnden 1994). Gallery systems

close to the ground at or below the lower limit of exit holes had short egg galleries. Bark

in this area of the bole is often wet, encouraging the growth of decay fungi that overgrow

D. confusus galleries. In contrast, the upper limit was characterized by wide variation in

Upper Limit

Lower Limit

19.5m

16.5 m

aie Resin Flow

¢ : : a =) :

et ge ae ee

a ?— =, a : ty ‘ . s :

Al ‘ a ea wn

¥ we we Ke f igen :

pO . a * " * ade

a 4 , ow, Tae

it r: ‘. <a raze st

BO LY a. We

2 ie Mint VY PMN

Exit Holes 7 / amma

xit Holes * “94 SERS

oe SN Galleries

a fe ee 8S Ces,

. ‘i ; is : ; s ‘ an .

‘ is ve Pa aoa

‘ int Toe NO af

: Ors ig if Ks ~ * i Gir h 3.5 m

re . Veg A

Hie \ gS

; a ' . 0.5 m

Figure 1. Upper and lower height limits for the majority of D. confusus galleries, exit

holes, and resin flow observed on felled red and grey subalpine fir.

0.5m

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 35

0) = Galleries

74) a Lower limit

D 40

D D

v0)

0 10

0 0

is 0) ts 0) :

Ee is Galleries

Upper limit

0) ce)

v0) D

10 10

0 0

0) Ee) Exit holes

0 a0 Lower limit

20 ce)

ec 0 0

gs » |

om a Exit holes

= Upper limit

3 » es pp

{<b}

Y nw | 2

40 10

0 la ; 0

SD D Resin Flow

40 40 Lower limit

x ce)

v0 2

10 10

(0) T T i T a | 0

0) 0)

fs 0 Resin Flow

_ A Upper limit

2 z0)

10 I 0

0 +—; i, 0

on OY HY YH Yo YH ww Hmnonn nn) oY oY Ho w

Bee eo Nene SPO eles re Coke 7d sie eae

Diameter (cm) Height (m)

Figure 2. Frequency distributions for upper and lower limits for D. confusus galleries, exit

holes and resin flow, based on bole diameter and height.

height, indicating a weak influence. The upper limit for resin flow, however, was tightly

clustered around 17.5 cm diameter (Figure 2), indicating a possible influence related to

diameter that limits D. confusus attack. The 17.5 cm upper limit diameter peak for resin

flow was greater than the average 10 cm upper limit for attack on trees that were

34 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

previously assessed by Stock (1991). This difference may indicate a different diameter

limit preference by D. confusus on standing trees versus downed trees.

A large percentage of subalpine fir basal area consisted of dead trees, totaling 31%,

28% and 25% for the single tree bait treatment, two-tree bait treatment and the control

area, respectively, at the time of baiting. These proportions are similar to those

documented by Unger and Stewart (1993) and Stock (1991). Parrish (1997) determined

that losses take place over a long period in subalpine fir stands, with some existing snags

having been dead for over 45 years. This slower, but continuous tree mortality affects

stand structure very differently than the devastation caused by mountain pine beetle to

mature pine stands.

D. confusus is likely the major mortality causing agent for standing dead trees at the

Sicamous Creek research area. The d.b.h. distribution of red and grey trees contained

more trees in the larger d.b.h. range (>20 cm d.b.h.), ranging in size between 19 and 49

cm, while the d.b.h. distribution of snags contained on average smaller trees, between 9

and 39 cm, similar to unattacked trees. Direct observation also confirmed D. confusus

activity in all felled red trees, 97% of the grey trees and 76% of snags examined (Table 4).

The greater percentage of small diameter trees among snags (Figure 3), suggests that the

smaller trees were killed by Armillaria ostoyae, a common root disease of conifers.

Merler (1997) found that 4. ostoyae killed mostly subdominant balsam and spruce at this

site.

Pheromone baiting trial

Baiting trial assessment. The ratio of mass attacked to red attacked trees in the single

tree and two-tree bait treatments was similar, and was significantly higher than in the

40 Unattacked

1 ee

0 = oo

ao Red N=713

P<0.0001

se 10

= 0 : | + + + + |_| 4

D 50

vanes Grey N=55

3 P<0.0001

& Bw

r 2

ty)

. Snag N=255

bad P<0.0001

° a |

0 ; | :

9.0 19.0 29.0 39.0 49.0

to to to to cts

dbh (cm)

Figure 3. Frequency distribution by diameter class of unattacked, red, grey and snag

subalpine fir. The DBH distribution of red, grey and snag trees were significantly different

from non-attacked trees (chi square analysis).

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 35

control area (Table 5), despite differences in the numbers of red trees per hectare among

the three areas in the pheromone baiting experiment. Trees in the two-tree bait treatment

area were more frequently mass attacked than those in the single tree baiting area (Table

5).

Table 5

Comparison of numbers and ratios of grey, red and newly mass attacked subalpine fir in

baited and control areas.

Number of affected subalpine fir/ha

Mass Mass attacked: Red:

Treatment area attacked Red Grey Red * Grey *

Control 4.4 18.5 5 0.24a 1.19a

Single tree baited 4.9 8.7 23.6 0.56b 0.37b

Two-tree baited 14.2 DA fe. 19.6 0.52b 1.40c

“ Proportions followed by the same letter are not significantly different, y?, P<0.001

Single-baited trees were consistently mass attacked. Spillover attack (attack on trees

directly adjacent to a baited tree, resulting from the bait treatment) was highest out to 1 m

away from the bait centres (Figure 4), and decreased at greater distances. Eighty percent

of mass attacks occurred within 9 m of single tree bait centres.

In the paired bait treatments, mass attacks peaked within 3 to 4 m of the bait centre,

apparently corresponding to half the distance between two bait trees (Figure 4).

Cumulative mass attacks increased to 60% of total mass attacks within 5 m of the bait

centre. At 10 m, 75% of all cumulative attacks had been recorded.

The aggregation pheromone (+)-exo-brevicomin used in the baiting trial successfully

concentrated D. confusus attacks on and around bait centres (Figure 4). However, it was

unclear whether the higher ratios in the baited vs. control areas were caused by retaining

dispersing beetles within the baited areas, attracting beetles into those areas (Table 5) or

spreading the same number of beetles among more trees. Baits used for spruce beetle

seem to have a limit of 25 meters efficacy (Shore et a/. 1990), and Gray and Borden (1989)

found that the influence of pheromone baiting for mountain pine beetle extended up to 75

m from grid-baited stands. Stock et al. (1994) observed consistently higher mass attacked

to red ratios within baited blocks than in 50 m wide buffer strips surrounding the blocks.

This suggests at least a 50 m range of influence on D. confusus. |

Comparison of insect development in baited and naturally attacked subalpine fir.

There was great variation in the utilization of both baited and naturally attacked trees

by western balsam bark beetle, ranging from trees with few gallery systems and little

brood to those having long galleries occupying a large proportion of the bole with

advanced brood development. Naturally mass attacked trees had more advanced brood

development (Table 6) and a greater percentage of the bole was occupied (Harder 1998).

The average meters of egg galleries and average density of egg galleries were less in

the naturally mass attacked trees than in the mass attacked, baited trees (Figure 5). Mean

egg gallery length however was not different between natural and baited trees (Fig. 5)

indicating more egg galleries constructed in baited trees. Some trees with low attack

density had high numbers of D. confusus parent adults per gallery system (up to 10).

These gallery systems were stained black, evidence of the fungus Ophiostoma

dryocoetidis. Western balsam bark beetle is closely associated with this pathogenic fungus

(Garbutt 1992; Bleiker et al. 2003). Initial beetle attacks may be pitched out and O.

dryocoetidis introduced, which in turn facilitates successful subsequent attack by the

36 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

1 tree bait centres 2 tree bait centres

80 80 Attack

60 60

40 40

20 20

0 0)

123 45 67 8 9 10 tT. ©3325" 7 9-10 13045

no)

iv.

zi 80 80 Nines

= 60 60 Attack

é 20 20

0 )

dive MOM amo OM Oe om Ti 3h Se 7 <9 ts aS

80 80 All Attack

60 60 (attack and

40 40 mass attack

50 20 combined)

0 0

12 eA 5 6 se7 Se OanOn 10 Soe Sea

Distance from bait centres (m)

Figure 4. Distribution of attacked trees (% trees) at one bait and two bait tree centres.

Solid bars indicate % attack at 1m intervals. Clear bars indicate cumulative attack.

beetle. Coalescing lesions caused by the fungus may also girdle and kill the trees without

any further beetle activity (Garbutt 1992). Egg galleries were so close together in baited

trees that the centre of the gallery system was completely excavated, and the nuptial

chamber and brood galleries were no longer distinguishable. This high density of gallery

construction and subsequent brood activity make certain characteristics of the gallery

system obscure. It is possible then, that D. confusus was confined to a limited area in

some baited trees because the tree would not have been susceptible to attack had it not

been baited (Bleiker et al. 2003)

In 1995, colonization by secondary scolytids was limited to Crypturgus borealis and P.

minutus. The year following mass attack, P. minutus was present in much larger numbers

in half of the baited trees examined (Harder 1998). Rhizophagus dimiatus and C. borealis

were found primarily in trees with advanced western balsam bark beetle brood

development (Table 6). R. dimiatus is a bark beetle predator and may use D. confusus

pheromones to locate its prey.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 By,

Mean egg gallery length

df=1

N=1596

F=7.43

P<0.06

mm (+SE)

Mean metres of

bole occupation

df=1

N=23

F=4.95

P<0.040

m (+ SE)

Mean metres of

egg gallery/m?

of=1

N=130

F=9.13

P<0.003

m/m? (+SE)

Mean number of

egg galleries/m?2

of=1

F=9.88

P<0.002

Mean number of

gallery systems/m2

df1

N=183

F=4.81

P<0.030

unbaited baited

Figure 5. Comparison of mean D. confusus egg gallery length (cm), bole occupancy (m),

and number of egg galleries per m’ in non-baited and baited subalpine fir.

No./m? (+SE)

Signs and symptoms (Dissections of mass attacked trees).

Trees classified as mass attacked in 1995 were divided into those turning red and those that

remained green. Fourteen trees with red foliage had larvae, evidence of successful attack,

while four of the eight trees that were still green had parent adults only. Only one of these

trees also had larvae, suggesting a delayed or partially successful attack. The four other

green trees had no successful adult activity or brood development. In oné-year-old attacks

with green foliage, gallery systems from the previous year were generally abandoned, with

few surviving brood. New, vigorous gallery excavation often began some distance from

old gallery areas. The affected trees likely responded to pathogenic infection by

producing traumatic resin at the sites of inoculation (Berryman and Ashraf 1970). New

attacks were initiated elsewhere to avoid the toxic areas. The trees that were mass attacked

in 1995 went through a rapid colour change between June and August 1996, from green to

bright red. Because foliage does not change to red until August, aerial surveys should not

be done until late summer or early fall.

The changes in foliage colour and the continued production of frass in mass attacked,

baited trees one year after baiting is consistent with their original classification. Foliage

colour change, frass production and renewed resinosis in trees originally classified as light-

attack, indicates that adults were able to survive, while allowing a year for associated

pathogenic fungi to overcome tree defenses. Lightly attacked trees could still be attractive

to attacking beetles one year after baiting. In an operational setting, all mass attacked trees

38 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Table 6

Occurrence of resin flow, D. confusus life stages and associated bark beetles in felled

baited and naturally mass attacked trees.

% Mass attacked

trees affected

Baited Natural

Observation * (n=10) (n=13) Remarks

Resin flow 30 69

D. confusus adults 100 100

eggs 90 92

small larvae 60 69

medium larvae 30 46

large larvae 0 30

Secondary scolytid, 10 p13 Only a few adults in newly

probably Pityokteines established galleries above zone of

minutus D. confusus colonization.

Crypturgus borealis 40 69 Found in 100% of trees with

medium or large larvae and 50% of

other trees, with galleries

constructed adjacent to D. confusus

galleries, often in large numbers.

Rhizophagus dimiatus 40 76 Predaceous, found in association

with D. confusus

“Small, medium and large larvae may correspond to the first three of four larval instars

(Stock 1991), however head capsule measurements were not made.

should be removed at harvest. Lightly attacked trees should also be considered for

removal because they could still be high risk. Heavily attacked trees turn colour quickly,

whereas lightly attacked trees may require more than one year to show colour change.

Less than half of the 23 mass attacked trees felled and assessed in the single-bait and

non baited areas at Sicamous Creek, had obvious signs of external resin flow originating in

the year of attack (1995). Nine trees had resin flow above and overlapping the area

occupied by D. confusus, and two trees had resin flow contained within that area. There

was a greater number of gallery systems attempted in resin flow areas, but with fewer,

shorter egg galleries. There were significantly greater proportions of failed gallery

systems in resin flow zones compared to those in non-resinous areas (Chi square,

P<0.001). In other words, resin flow appears to inhibit the success of egg gallery

production. The invading beetles are pitched out from the tree and if the pathogenic

fungus O. dryocoetidis is not successfully introduced, then the attacked tree will most

likely survive. The presence of resin on the bole, therefore, indicates unsuccessful attack.

Typically, successfully mass attacked trees do not have copious amounts of resin on the

bole but instead may present a large amount of frass.

Depending on the beetle pressure in a stand and individual susceptibility of baited trees

(Bleiker et al. 2003), attacks may range from unsuccessful or no attack, to successfully

mass attacked. It appears that often in the initial year of attack, D. confusus will initiate

nuptial chambers but very few egg galleries in the attacked tree. During the late summer

flight, made up primarily of females (Stock 1991), additional females can enter existing

nuptial chambers and begin excavating new egg galleries. This extended period of attack

on a baited tree would, in part, explain the variability in colour change observed.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 39

CONCLUSIONS

Harvesting removes beetle-infested trees. While eliminating all D. confusus infested

trees in the cut areas, the 1.0 ha and 10 ha clearcuts left populations relatively untouched in

the buffer strips. In harvesting the 0.1 ha and single tree selection areas, most of the snags,

grey and red trees were removed in spite of the fact that logging occurred without

conscious effort to remove beetle-attacked trees. In B.C., harvesting of this type requires

that all dead trees be removed for safety reasons. Even without baiting, most infested trees

were removed from the area, leaving a portion of new 1994 mass attacked trees as sources

of new infestation. Pre-harvest baiting of these stands would have allowed removal of

most new 1994 mass attacked trees as well.

While the short-term benefits of reducing D. confusus populations in single tree

selection and patch cut systems are evident, in the long term, the possibility of windthrow

exists in single tree selection and patch cut areas (Novak et al. 1997). Stands harvested by

single tree selection may be too open (Coates 1997), while patch cut stands are fragmented

and have a large ratio of edge relative to patch size (Novak ef al. 1997). Build up of D.

confusus populations in windthrow could possibly jeopardize the remaining standing trees

resulting in populations too large for pheromone-based management. Moreover, mortality

due to root and butt rot pathogens tends to increase to very high levels in stands that are

partially cut (Morrison ef a/. 1991).

Pheromone baiting to manage D. confusus populations when conducting single tree

selection or patch cut systems is recommended. By varying the number and placement of

bait trees, it is possible to reduce the resident population of D. confusus. The attractive

power of baits seems to be sufficient to draw the majority of adult D. confusus from buffer

strips into very small areas designated for cutting. Operational tests should be done over

time to develop protocols for pheromone baiting that are consistent with a wide variety of

possible harvesting regimes and infestation levels.

Subalpine fir should be considered in conjunction with the many other species present

in high elevation ecosystems. The relationship between D. confusus and root diseases

should be further explored. At present, root disease induced mortality appears limited to

suppressed subalpine fir and spruce (Merler 1997), in spite of long-term disturbance due to

D. confusus. Wildlife species-such as mountain caribou may depend on old growth stand

characteristics (Armeler and Waterhouse 1994) in high elevation ecosystems. There are

concerns that birds, such as the three-toed woodpecker depend on snags for habitat and/or

food (Klenner and Huggard 1997). Backhouse and Louiser (1991) list over 90 species of

vertebrates that utilize snags for a variety of purposes. A large number of invertebrates,

bryophytes, and lichens are also likely to depend on large dead trees. Thus, there are many

reasons to be cautious about removing D. confusus from A. lasiocarpa stands. The

possible conservation importance of stands characterized by large A. /asiocarpa and the D.

confusus dynamics contained within them may limit harvesting and managing options.

ACKNOWLEDGEMENTS

We gratefully acknowledge Connie Harder for her support and assistance and Lynn

Kristmanson for her artwork. This study was funded in part by Forest Renewal B.C. and

the B.C. Forest Service.

40 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

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J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 43

Diversity, distribution and phenology of Lygus species

(Hemiptera: Miridae) in relation to vegetable greenhouses in

the lower Fraser Valley, British Columbia, and southwestern

Ontario

D. R. GILLESPIE

AGRICULTURE AND AGRI-FOOD CANADA, PACIFIC AGRI-FOOD RESEARCH

CENTRE, AGASSIZ, BC VOM 1A0

R. G. FOOTTIT

AGRICULTURE AND AGRI-FOOD CANADA, EASTERN CEREAL AND OILSEEDS

RESEARCH CENTRE, OTTAWA, ON, K1A 0C6

J. L. SHIPP

AGRICULTURE AND AGRI-FOOD CANADA, GREENHOUSE AND PROCESSING

CROPS RESEARCH CENTRE, HARROW, ON, NOR 1G0

M. D. SCHWARTZ

AGRICULTURE AND AGRI-FOOD CANADA, EASTERN CEREAL AND OILSEEDS

RESEARCH CENTRE, OTTAWA, ON, K1A 0C6

D. M. J. QUIRING

AGRICULTURE AND AGRI-FOOD CANADA, PACIFIC AGRI-FOOD RESEARCH

CENTRE, AGASSIZ, BC VOM 1A0

KAIHONG WANG

AGRICULTURE AND AGRI-FOOD CANADA, GREENHOUSE AND PROCESSING

CROPS RESEARCH CENTRE, HARROW, ON, NOR 1G0

ABSTRACT

Lygus spp. were collected from near and inside vegetable greenhouses during three

years in the lower Fraser Valley, British Columbia (BC) and in Leamington, Ontario

(ON). In BC, the dominant species was Lygus shulli, followed in abundance by L.

elisus and L. hesperus; L. lineolaris was not collected in the lower Fraser Valley. In

ON, only L. lineolaris was collected. In BC, L. shulli was generally distributed

throughout the region, whereas L. hesperus was captured in sweep net samples only in

coastal areas. Lygus hesperus appeared to be univoltine in BC. All other species in ON

and BC were apparently bivoltine. In ON, numbers of adults collected outside of

greenhouses correlated with numbers collected inside greenhouses whereas this was not

the case in BC. Differences in flight behaviour, abundance and greenhouse construction

may account for this latter difference. Our results highlight the need for different

approaches to IPM of pest Lygus species in the ON and BC greenhouse industries.

44 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

INTRODUCTION

Lygus bugs, Lygus spp. are important pests of crops throughout Canada (Philip 1997,

Schwartz and Foottit 1998, Braun et al. 2001). They are known to attack greenhouse

vegetable crops in both British Columbia (BC) and Ontario (ON) (Howard et al. 1994,

Broadbent and Murphy 1997, Gillespie and Foottit 1997, Gillespie et al. 2000). All

species that are pests seem to be associated with either alfalfa or weedy habitats and to

invade from those habitats into crops (Khattat and Stewart 1980, Fye 1982, Schwartz and

Foottit 1992a, Gerber and Wise 1995, Broadbent et a/. 2002, )

In light of the recent taxonomic revision of the Nearctic Lygus (Schwartz and Foottit

1998) knowledge of the pest species distribution and occurrence with respect to

greenhouse crops needs to be updated so that pest managers are making up-to-date

recommendations. Surveys of canola have reported shifts in the complex of Lygus spp.

(Butts and Lamb 1991, Schwartz and Foottit 1992b, Carcamo et al. 2002).

The timing of adult flights and occurrence of immatures is important for making pest

management decisions for crops where Lygus spp. are pests (Butts and Lamb 1991, Varis

1995). Yellow sticky traps are a useful tool for gathering this information (Luczynski et al.

1997), and are more practical than sweep net samples for evaluation of numbers in

greenhouses.

The objectives of this study were to survey the Lygus complex associated with weedy

habitats near greenhouse crops in two key greenhouse production regions, the Lower

Fraser Valley, BC and southwestern ON, and to determine the phenology of the key

species.

MATERIALS AND METHODS

BC 1996 Collections. In 1996, 60 collections of Lygus spp. adults were made at

approximately two wk intervals at 22 localities throughout the lower Fraser Valley and

immediate surroundings between 7 May and 19 September to determine the diversity of

Lygus spp. in weedy habitats around greenhouses. Sampling was conducted with a

standard insect sweep net; each sample consisted of 100 sweeps made in a 180° arc.

Some localities were sampled at least three times, which provided a measure of changes in

numbers over time.

In greenhouses, adult Lygus spp. were monitored using yellow sticky traps (30 x 60

cm, Phero Tech Inc, Richmond, BC ) placed in each of six commercial greenhouses in the

lower Fraser Valley starting on 23 April. Additional yellow sticky traps were placed on 60

cm tall posts in eight, low-growing, weedy, locations. Traps were oriented in an east-west

direction. Three of these were within 10 m of greenhouses which had traps placed inside,

two were adjacent to greenhouses without traps, and three were in locations approximately

1 km from greenhouses, in Agassiz, Chilliwack and Abbotsford, BC. Traps were replaced

every two weeks, from 7 May to 20 September and the Lygus adults on the traps identified

to species and counted.

BC 1997 Collections. In 1997, 25 sweep net collections were made between 2 April

and 26 September, as in 1996. These collections were made in weedy habitats, generally

within 100 m of greenhouses. On 29 June and 20 August, additional collections were

made on east-west and north-south routes through the valley, from Ladner on the coast to

Rosedale, near the head of the valley, and from Aldergrove, BC, on the Canada/US border

to Mission, BC, on the north side of the Fraser River. We made 18 collections on 29 June

and 23 on 20 August. The purpose of these samples was to provide data on species

distribution within the Fraser Valley.

As in 1996, yellow sticky traps (30 x 60 cm) were placed on 60 cm posts at 10

locations in weedy fields and near greenhouses. The traps were changed every two weeks,

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 45

and the Lygus spp. collected were counted and identified. No collections were made in

greenhouses.

BC 1998 Collections. In 1998, 103 sweep collections were made in weedy vegetation

at 25 locations through the Fraser Valley, from 2 April to 26 September. These locations

were at sites either within 100 m of greenhouse, or isolated from greenhouses by

approximately 1: km. Ten of these locations were visited every two weeks from 2 April to

26 September. It was not possible to collect at every site in every interval because of rain.

Lygus spp. adults and 4th and 5th instar nymphs were removed from the samples. The

nymphs were reared in the laboratory to the adult stage on snap-beans and cauliflower

pieces. The number of nymphs of each species was determined for each two week interval.

Yellow sticky traps (30 x 60 cm) were placed in nine locations within 10 m of

commercial greenhouses. Traps were replaced every two weeks and the Lygus spp. on

them were counted and identified. Inside each of these greenhouses, 10 small, yellow

sticky traps (12.7 x 7.6 cm, Phero Tech Inc, Richmond, BC) were suspended on the trellis

wire, 10 to 50 cm above the crop and approximately 10 m apart. These also were changed

every two weeks, and the collected Lygus spp. counted and identified. Crops in the

greenhouses (numbers of greenhouses) were tomato (1), cucumber (2) and pepper (6).

Ontario Field Survey. Surveys were conducted in three fields located at Pyramid

Farm, Andrew Prytocki Farm and Chris Tiessen Farm in the Leamington area, Essex

County, ON at two week intervals from 4 June to 9 September, 1997 and from 5 May

through 6 October 1998. The sampling sites were < 10 m from greenhouses and in dense

weed cover. On each sample date, 100 sweeps were taken at each site. Lygus spp. adults

and nymphs were counted and identified.

Ontario Greenhouse Survey. Monitoring was conducted on greenhouse sweet pepper

at one_greenhouse in the Leamington area from May through October in 1997 using five

small yellow sticky traps (12.7 x 7.6 cm, Phero Tech Inc, Richmond, BC) that were placed

over five rows of pepper plants (total of 0.5 ha area). Traps were approximately 30 cm

above the crop and traps were approximately 10 m apart. At the same time, Lygus spp.

populations were surveyed by visual inspection of five rows of plants (212 plants/row)

with four sampling units per row and five plants per unit. For each plant, the growing tip

and flowers of two stems were checked for Lygus nymphs and adults. In 1998, monitoring

was conducted from May through October, with 10 traps placed over 10 pepper rows and

visual inspections of 10 rows of plants with two sampling units per row and five plants per

sample unit.

Specimens and Records. Specimens of the dominant plants present in the sampled

habitats were collected and identified. All Lygus spp. adult material was pinned and

identified and voucher specimens were placed in the Canadian National Collection of

Insects (Agriculture and Agri-Food Canada, Ottawa) (CNC). Historical records of Lygus

spp. in the lower Fraser Valley were extracted from a database of records in Canada

compiled by Schwartz and Foottit (1998). These records were compared with those

documented during this study to determine any changes in distribution.

Data Analysis. Data were grouped by week to allow comparison between years. For

each species locality data was pooled across all years for trap and sweep collections. The

relationships between counts of insects outside and inside greenhouses were tested with

Pearson correlation (CORR procedure) using SYSTAT 7.0 (SPSS 1997).

RESULTS

Extant Lygus. In southwestern ON, only Lygus lineolaris (Palisot de Beauvois) was

collected over both years of sampling. Sampled weed hosts were ragweed, Ambrosia

artemisiifolia L., smartweed, Polygonum persicaria L., green foxtail, Setaria viridis (L.)

Beauv., red clover, Trifolium pratense L. and pigweed , Amaranthus retroflexus L.

46 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

In BC, Lygus shulli Knight, Lygus elisus Van Duzee and Lygus hesperus Knight were

collected over the three year survey. Depending on location, the sampled habitats

contained grasses, mainly Festuca and Bromus spp, red clover, Trifolium pratense L.,

Dutch white clover 7. repens L. shepherd's purse, Capsella bursa-pastoris (L.) Medic,

chamomile, Matricaria maritime L., stinking mayweed, Matricaria chamomilla L.,

dandelion, Taraxacum officianale Weber, and various unidentified mustards

(Brassicaceae). Based on the total numbers collected in sweep samples and on traps over

the three years, L. shulli represents about 79% of the Lygus, L. elisus about 15% and L.

hesperus about 6%. Individual species, however, varied in abundance at specific locations

and in particular years. Lygus lineolaris was not collected in the Fraser Valley in 1996,

1997 or 1998.

Historical Records. Records in Schwartz and Foottit (1998) and in the North

America Lygus database provide a historical record of the diversity of Lygus spp. in the

lower Fraser Valley. The specimens representing the records for the Fraser Valley were

validated by M.D. Schwartz, and were housed in the Spencer Entomological Collection

(SMDV) at the University of British Columbia and in the CNC. Lygus shulli is

represented by 65 specimens, collected from 1922 to 1996 and housed in both collections.

Lygus hesperus is represented by 31 specimens collected from 1923 to 1996, all at the

SMDV. Lygus elisus is represented by 23 specimens collected between 1923 and 1996,

present in the CNC and the SMDV. Lygus lineolaris is represented by 27 specimens

collected between 1923 and 1965 in the lower Fraser Valley, all of which are housed in the

SMDV.

Distribution. In general, L. shulli was widely distributed in the lower Fraser Valley,

and occurred in most samples and at all locations (Fig. 1). Lygus elisus was also widely

distributed, although this species was collected in fewer locations than L. shulli. In

contrast, L. hesperus was collected primarily in the locations close to the coast, with a

small number of individuals occurring in scattered locations through the remainder of the

region. Because L. lineolaris was the only species noted around greenhouses in the

Ontario collections and was collected at all locations, its local distribution was not

mapped.

Ontario phenology. In 1997, a few adult L. /ineolaris were collected outdoors in June,

the first nymphs were noted in early July, and the peak of the first generation appeared in

early August (Fig. 2). A second generation followed in early September, indicated by an

increase in nymphs in collections (Fig. 2). Collections were not continued to the end of

this second generation in 1997. In 1998, a few adults were collected at the beginning of

May. The first generation peaked in the middle of July and a second generation peaked

around the end of September.

In greenhouses in 1997, the first L. Jineolaris were sampled in mid June (Fig. 2). The

numbers increased to about 1.8 adults per trap. A pesticide was applied by the greenhouse

grower after the early June collection to reduce the numbers of nymphs on the plants. In

1998, Lygus adults were first seen in early May, along with nymphs. The population of

Lygus adults increased to 3 adults/trap by the end of June. By 22 September, a second

generation peaked at 3.9 adults/trap.

BC phenology. Adults of L. shu/li were collected in sweep samples starting in May in

1996 (Fig 3A) and adults of both L. shulli and L. elisus were collected in April in 1998

(Figs. 4A, B). In 1998, nymphs of the first generation of both L. shulli and L. elisus

appeared in sweep collections when the numbers of adults were low, in early June. The

first generation of nymphs of L. shulli completed development by mid July, and nymphs of

the second generation appeared in the field in late July. The first generation nymphs of L.

elisus completed development in early July, and nymphs of the second generation

appeared in late July. More adults than nymphs of L. elisus were caught. There was no

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 47

Figure 1. Distribution of Lygus spp. in the lower Fraser Valley, British Columbia, based

on sampling in 1996, 1997 and 1998. A-C Sweep samples: A. Lygus shulli; B. L. elisus; C.

L. hesperus. D-F yellow sticky trap captures: D. L. shulli; E. L. elisus; F. L. hesperus.

Open circles designate locations where the relevant species was not captured, and closed

circles are locations where that species was captured. The right border of the maps is at

121° 50’ West. The dashed line indicates the approximate boundary of the lower Fraser

Valley.

evidence of a third generation of either L. shulli or L. elisus. Adults of L. hesperus were

collected in sweep samples only in late June and early July (Figs. 3A, 4C), and nymphs

were collected only in July and August (Fig. 4C).

Sticky trap collections outside of greenhouses showed that a flight of L. shulli occurred

in May in both 1996 and 1998 (Figs. 3, 5). These were probably adults dispersing from

overwintering sites. Numbers of L. shulli adults on traps declined in June, increased in July

48 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

A. Field, 1997 gum adults

C— nymphs

C. Field, 1998 a adults

C— nymphs

number per 100 sweeps

16 B. Greenhouse, 1997 @@—Mm® adults on traps

C— nymphs in counts

1g | 0. Greenhouse, 1998 gage adults on traps

C— nymphs in counts

Adults on Yellow traps and nymphs on plants

8 8

6 6

4 4

2 2

0 0

Ms we ey ee Rs Ree eis re wit ae we yo rs a ae 7

Figure 2. Numbers of Lygus lineolaris in sweep net samples near greenhouses, in counts

on pepper plants, and-on yellow sticky traps in pepper greenhouses in southwestern

Ontario in 1997 and 1998. A, C: Mean number (+SE) of adults and nymphs in 100 sweeps

in 1997 and 1998 respectively. B, D: numbers of adults per sticky trap and numbers of

nymphs in surveys of 100 plants in 1997 and 1998, respectively.

and August, and decreased again in September. On traps outside of greenhouses, L. elisus

also showed an early flight of overwintering adults in May (Figs. 3B, 5A). Like L. shulli,

adults declined on traps in June and July. Adults then increased in numbers on traps in

August and September, but this increase occurred somewhat later than L. shulli, perhaps

indicating a longer developmental period. Lygus hesperus was never captured on traps

outside of greenhouses in May (Figs. 3, 5). Adults of L. hesperus were noted on traps only

in early August in 1996 and in August and September, 1998. The abundance of adults in

sweep collections coincided with the results from traps outside of greenhouses.

Adults were relatively rare on yellow sticky traps inside greenhouses (Figs. 3C, 5B).

The most abundant species was L. shulli, followed by L. elisus. Only one specimen of L.

hesperus was captured on a yellow sticky trap inside a greenhouse. In general, captures of

adults on traps inside greenhouses coincided with times when adults were captured on

traps outside of greenhouses. Lygus shulli appeared in early May in 1996 and in mid June

in 1998 in greenhouses, but L. e/isus was not seen until mid August in 1996 and in mid

June in 1998 (Figs. 3, 5). Lygus hesperus was not collected on traps in greenhouses in

1996, and only in late September in 1998 (Figs. 3, 5)

Correlation of field and greenhouse samples. Numbers of adults caught in sweeps

outside of greenhouses in ON correlated with numbers of adults on traps in greenhouse in

1997 but not in 1998 (Pearson Correlation Coefficient (PCC) = 0.628, Bartlett’s v=

10.76, P < 0.0001 and PCC = 0.303, Bartlett’s x = 2.33, P = 0.073, respectively). No

correlation was found between numbers of Lygus spp. adults in field sweeps and numbers

of Lygus spp. on traps in greenhouses in 1996 or 1998 (PCC = 0.152, Bartlett’s xX = 0.195,

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 49

P = 0.659, and PCC = -0.074, Bartlett’s ¥ = 0.352, P = 0.553, respectively). Similarly, no

correlations were found between the numbers of L. shulli on traps in field sites and in

nearby greenhouses in 1996 or 1998 (PCC = 0.553, Bartlett’s xX = 1.729, P = 0.189, and

PCC = 0, Bartlett’s x = 0.000, P = 0.998, respectively).

Be essnull

” 20 L. elisus

oo mum | hesperus

S 15

ro)

2 10

46 4 B. Outside traps C— L. shulli

L. elisus

Qa 14 Mmmm | hesperus

a 2

am 10

> 8

es)

=> 4

C. Inside traps

C— L. shulli

L. elisus

lygus adults per trap

Figure 3. Mean captures (+SE) of L. shulli, L. elisus and L. hesperus in the lower Fraser

Valley, BC in 1996. A. Average captures in 100 sweeps. B. average captures on yellow

traps outside of greenhouses. C. Average captures on yellow traps inside greenhouses

50 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

100

w A. L. shulli

@ 807 > Adults

= Nymphs

S 60

Q 40

fe!

E 20

B. L. elisus

c— Adults

Nymphs

Number per 100 sweeps

C. L. hesperus

Cc— Adults

Nymphs

Number per 100 sweeps

Figure 4. Mean captures (+SE) of adult and immature L. shulli, L. elisus and L. hesperus

in sweep net samples in the Lower Fraser Valley, BC in 1998: A. L. shulli; B. L. elisus; C.

L. hesperus.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 5]

A. Outside greenhouses Ci L. shulli

14 L. elisus

Game |. hesperus

number per flight trap

(oe)

RMQQY

B. Inside greenhouses CT L. shulli

L. elisus

Mmmm |. hesperus

Number per ten traps

Figure 5. Mean captures (4SE) of L. shulli, L. elisus and L. hesperus on yellow sticky

traps in the lower Fraser Valley, BC in 1998. A. Captures outside of greenhouses. B.

Captures inside greenhouses.

DISCUSSION

The historical collection records for the Fraser Valley show that L. lineolaris was once

one of four Lygus spp. in the region. This species was not collected in the current study,

strongly suggesting it has either been extirpated or reduced dramatically in numbers in the

lower Fraser Valley. Day (1996) noted dramatic decreases in abundance of L. lineolaris in

alfalfa fields in eastern North America following the establishment of the exotic bivoltine

parasitoid, Peristenus digoneutis Loan (Hymenoptera: Braconidae). Impacts of a parasitoid

would not appear to be involved in BC, since a) parasitism in 1998 samples averaged only

5% by a univoltine Peristenus sp. attacking only the first generation (Gillespie,

unpublished data), and b) L. lineolaris has been collected routinely in the interior and

52 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

eastern regions of British Columbia in the last decade based on collections records at the

CNC.

In Ontario, numbers of L. lineolaris on traps in greenhouses were correlated with

numbers caught in sweeps in nearby fields in one year but not in another. The correlation

in 1997 may have actually been due to a pesticide application against L. lineolaris nymphs

that were present in the greenhouse in 1997. The consequence of this was adults emerging

in the greenhouse were not present and the relationship between sticky trap catches in

greenhouse and field was not affected by these adults. In BC, numbers of Lygus spp. on

traps inside of greenhouses were not related to numbers of Lygus spp. in sweep collections

or on traps outside of greenhouses. The difference between the BC and ON results may be

a consequence of either differences in species' plant location and flight behaviour, or

differences in the physical structure of the greenhouses.

Little is known about host plant location and flight behaviour in Lygus spp. Cleveland

(1982) reported that L. lineolaris moves from spring weed hosts into cotton fields when the

latter were at the most susceptible stage. Stewart and Gaylor (1994) showed that females

with chorionated eggs were more likely to fly than females without eggs, supporting

observations that young reproductive females were most likely to invade crops. Rancourt

et al. (2000) showed that flight in L. /ineolaris was predominantly 1 m from the ground. It

is possible that the species in BC differ in their host location and flight behaviour from L.

lineolaris to the extent that they are less likely to invade greenhouses.

The flight behaviour of L. shulli and L. elisus has not been studied. Increases in the

numbers of adults of both species in sweep samples preceded the increase in numbers on

traps (Fig. 4A) by 2-4 weeks, suggesting that newly matured adults do not immediately

move from their development locations. Adults of both ZL. shulli and L. elisus continued to

increase in sweep samples until the last collections in late September. However, adults of

both species on traps declined through September. This suggests that the sweep sample

locations were also overwintering habitats, or at least very close to overwintering habitats,

and that adults did not disperse from this habitat.

The greenhouse industries in the lower Fraser Valley of BC and southerwestern

Ontario typically use different greenhouse structures. The Ontario industry favours double

polyethylene greenhouses that have side-wall vents, that is, vents that open at or near to the

ground surface. In contrast, the BC industry favours glass greenhouses that that have vents

only on the roof, 4 m or more above ground level. If flight at approximately 1 m above

ground level is typical of Lygus spp., then in Ontario, invasions of L. lineolaris into

greenhouses through ground-level vents would be driven by field populations. In BC,

invasions through roof vents or doorways would be random events and _ therefore

unpredictable. Finally, there is a difference in the numbers of Lygus spp. adults in sweep

samples in the field in BC and Ontario. In Ontario, captures exceeding 150 adults per 100

sweeps occurred, whereas in BC captures are typically one-tenth of that number. Thus, the

differences in correlation between field and greenhouse numbers could be due to

differences in field populations in the two regions making greenhouse invasion in BC less

likely than in Ontario.

Carcamo et al. (2002) reported wide-scale changes in Lygus spp. diversity on the

prairies that were important for pest management. The differences in distribution of Lygus

spp. within the Fraser Valley, an area about 150 km on an east-west axis and 50 km on a

north-south axis, are also significant for pest management. Differences in abundance

among the three species may cause differences in significance in certain parts of the valley.

Differences among the species in behaviour, phenology or pesticide tolerances could mean

that growers would have to adopt different IPM strategies for the different species. For

example, L. elisus favours annual weedy Brassicaceae, whereas L. shulli prefers common

Asteraceae (Schwartz and Foottit 1998).

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 53

Nymphs of L. hesperus did not appear in 1998 until early August, two weeks after the

first adults had appeared in sweep samples and in traps outside of greenhouses. Based on

this result, L. hesperus appears to be univoltine in the lower Fraser Valley, and does not

occur in the field until after L. shulli and L. elisus have completed their first generation.

Lygus hesperus is a key pest of many crops in western North America (Kamm 1987,

Ruberson and Williams 2000, Udayagiri et a/. 2000), but in Canada, this species seems to

occur primarily along the western, coastal part of the Fraser Valley, and appears to be

univoltine. Thus, L. hesperus does not seem to be a major pest of agriculture in the Fraser

Valley. Distribution maps in Schwartz and Foottit (1998) suggest that the northern limit

for L. hesperus is in the southern BC area. This species may be univoltine in, or may

migrate annually into the northern part of its range. Either explanation would account for

the observed distribution.

We have shown regional differences in species distribution and phenology of Lygus

spp. near and in vegetable greenhouses between BC and ON. These differences will result

in growers taking different approaches to management of Lygus spp. in greenhouses.

ACKNOWLEDGEMENTS

We thank D. Higginson, J. Froese, C. Hilder, N. Sawyer for technical assistance in BC,

and G. Ferguson for assistance in collecting Lygus and selecting sites in ON. We also

thank E. Maw and G. Gillespie for preparing maps and assisting with preparation of

geospatial data, and P. Mason for a critical review of a previous version of this manuscript.

Partial funding for this project was provided by the Matching Investments Intitiative of

Agriculture and Agri-Food Canada, and by the BC Greenhouse Growers Association. This

is contribution number 694 from the Pacific Agri-Food Research Centre, Agassiz, BC.

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occurrence, species composition, and parasitism of Lygus spp. (Hemiptera: Miridae) in alfalfa, canola,

and mustard. The Canadian Entomologist 133: 565-578.

Broadbent, B. and G. Murphy. 1997. Lygus in Greenhouse Crops, pp 48-49. Jn J. Soroka (ed.),

Proceedings of the Lygus Working Group Meeting, Apml 11 and 12, 1996. Agriculture and Agri-Food

Canada Research Branch, Winnipeg, Manitoba.

Broadbent, A.B., P.G. Mason, S. Lachance, J.W. Whistlecraft, J.J. Soroka and U. Kuhlmann. 2002. Lygus

spp., Plant Bugs (Hemiptera; Miridae), pp. 152-159. In P.G. Mason and J.T. Huber (eds.), Biological

Control Programmes in Canada, 1981 - 2000. CABI Publishing, Oxon, UK.

Butts, R.A. and R.J. Lamb. 1991. Pest status of Lygus bugs (Hemiptera: Miridae) in oilseed Brassica

crops. Journal of Economic Entomology 84: 1591-1596.

Carcamo, H., J. Otani, C. Herle, M. Dolinski, L. Dosdall, P. Mason, R. Butts, L. Kaminski and O. Olfert.

2002. Variation of Lygus species assemblages in canola agroecosystems in relation to ecoregion and

crop stage. The Canadian Entomologist 134: 97-111

Cleveland, T.C. 1982. Hibernation and host plant sequence studies on tarnished plant bugs, Lygus

lineolaris in the Mississippi Delta. Environmental Entomology 11: 1049-1042.

Day, W.H. 1996. Evaluation of biological control of the tarnished plant bug (Hemiptera: Mindae) in alfalfa

by the introduced parasite Peristenus digoneutis (Hymenoptera: Braconidae). Environmental

Entomology 25: 512-518.

Fye, R.E. 1982. Damage to vegetable and forage seedlings by the pale legume bug, Hemiptera: Miridae).

Journal of Economic Entomology 75: 994-996.

Gerber, G.H., and I.L. Wise. 1995. Seasonal occurrence and number of generations of Lygus lineolaris and

L. borealis (Heteroptera: Miridae) in southern Manitoba. The Canadian Entomologist 127: 543-559.

Gillespie, D. and R. Foottit. 1997. Lygus bugs in Vegetable crops in B.C. pp. 7-9. Jn J. Soroka, (ed.),

Proceedings of the Lygus Working Group Meeting, April 11 and 12, 1996. Agriculture and Agri-Food

Canada Research Branch, Winnipeg, Manitoba.

Gillespie, D.R., R.G. Foottit, L. Shipp, M.D. Schwartz, K. Wang and D.M.J. Quiring. 2000. Lygus bugs in

protected crops - improving our understanding, pp. 1-8. /n R. Foottit and P. Mason (eds.), Proceedings

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of the Lygus Working Group Meeting, 26 September, 1999. Agriculture and Agri-Food Canada,

Research Branch, Saskatoon, Saskatchewan

Howard, R.J., J. Garland and W.L. Seaman. 1994. Diseases and Insect Pests of Vegetable Crops in

Canada. The Canadian Phytopathological Society and The Entomological Society of Canada, Ottawa,

Ontario.

Kamm, J.A. 1987. Impact of feeding by Lygus hesperus (Heteropera: Miridae) on red clover grown for

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Khattat, A.R. and R.K. Stewart. 1980. Population fluctuations and interplant movements of Lygus

lineolaris. Annals of the Entomological Society of America 73: 282-287.

Lucyzynski, A., R. Vernon and D. Henderson. 1997. Developing an efficient visual trap for Lygus in

Strawberries, p. 22. In J. Soroka (ed.), Proceedings of the Lygus Working Group Meeting, April 11

and 12, 1996. Agriculture and Agri-Food Canada Research Branch, Winnipeg, Manitoba

Philip, H.G. 1997. Lygus bugs in BC, pp. 44-45. Jn J. Soroka (ed.), Proceedings of the Lygus Working

Group Meeting, April 11 and 12, 1996. Agriculture and Agri-Food Canada Research Branch,

Winnipeg, Manitoba.

Rancourt, B., C. Vincent and D. de Oliveira. 2000. Circadian activity of Lygus lineolaris (Hemiptera:

Miridae) and effectiveness of sampling techniques in strawberry fields. Journal of Economic

Entomology 93: 1160-1166.

Ruberson, J.R. and L.H. Williams. 2000. Biological control of Lygus spp.: a component of areawide

management. Southwest Entomologist Supplement 23: 96-110.

Schwartz, M.D. and R.G. Foottit. 1992a. Lygus species on oilseed rape, mustard and weeds: a transect

across the Prairie Provinces of Canada. The Canadian Entomologist 24: 151-158.

Schwartz, M.D. and R.G. Foottit. 1992b. Lygus bugs on the prairies: biology, systematics and distribution.

Agriculture Canada Research Branch Technical Bulletin 1992-4E, Ottawa, Ontario.

Schwartz, M.D. and R.G. Foottit. 1998. Revision of the Nearctic Species of the Genus Lygus Hahn, with a

review of the Palearctic Species (Heteroptera: Miridae). Memoirs on Entomology, International,

Volume 10. Associated Publishers, Gainesville, Florida.

SPSS Inc. 1997. SYSTAT® 7.0 for Windows: Statistics. SPSS Inc, Chicago, IL.

Stewart, S.D. and M.J. Gaylor. 1994. Effects of age, sex and reproductive status on flight by the tarnished

plant bug (Heteroptera: Miridae). Environmental Entomology 23: 80-84.

Udayagin, S., S.C. Welter, and A.P. Norton. 2000 Biological control of Lygus hesperus with inundative

releases of Anaphes iole in a high cash value crop. Southwestern Entomologist Supplement 23: 27-38.

Varis, A.L. 1995. Species composition, abundance, and forecasting of Lygus bug (Heteroptera: Miridae)

on field crops in Finland. Journal of Economic Entomology 8: 855-858.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Abundance of Lygus spp. (Heteroptera: Miridae) in canola

adjacent to forage and seed alfalfa

H.A. CARCAMO!

AGRICULTURE AND AGRI-FOOD CANADA, LETHBRIDGE RESEARCH CENTRE,

PO BOX 3000, LETHBRIDGE, AB, CANADA TI1J 4B1

J. OTANI

AGRICULTURE AND AGRI-FOOD CANADA, BEAVERLODGE RESEARCH FARM,

BOX 29, BEAVERLODGE, AB, CANADA TOH 9C0

J. GAVLOSKI

MANITOBA AGRICULTURE AND FOOD,

65 - 38” AVE N.E., CARMAN, MB, CANADA ROG 0J0

M. DOLINSKI

ALBERTA AGRICULTURE, FOOD AND RURAL DEVELOPMENT,

7000 B 113 STREET, EDMONTON, AB, CANADA T6H 5T6

and J. SOROKA

AGRICULTURE AND AGRI-FOOD CANADA, SASKATOON RESEARCH CENTRE,

107 SCIENCE PLACE, SASKATOON, SK, CANADA S7N 0X2

ABSTRACT

Our objectives were to document the abundance of lygus bugs (Mindae) in canola after the

cutting of adjacent alfalfa hay fields and to document their seasonal activity in canola plots

grown in close proximity to alfalfa seed. Cutting alfalfa did not increase abundance of

lygus bugs in nearby canola in sites near Barrhead, Alberta (1998-1999), in the Peace River

area of British Columbia (2000) or near Carman, Manitoba (2001). In Saskatoon, from

1993-1995, lygus bug numbers remained at low levels in seed alfalfa and canola and there

was no indication that the pest species (L. lineolaris) in canola moved in significant

numbers from the adjacent alfalfa seed field. We conclude that alfalfa forage harvesting

generally does not result in massive movement of lygus bugs to nearby canola.

Key words: Lygus bugs, canola, alfalfa, forage harvest

INTRODUCTION

Lygus bugs (Miridae) feed on actively growing meristematic tissue, particularly buds,

flowers and immature seeds, which may result in economic losses to many crops throughout

North America and Europe (Young 1986). In Alberta the most common Lygus (Hahn) species

are L. lineolaris (Palisot de Beauvois), L. borealis (Kelton), L. elisus (Van Duzee), and L.

keltoni (Schwartz) (Carcamo et al. 2002). The latter species does not occur east of Alberta and

L. lineolaris is rare in the mixed and short grass prairie ecoregions (Schwartz and Foottit

'To whom correspondence should be addressed. (Email: carcamoh@agr.gc.ca)

56 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

1998). Lygus bugs are a primary pest of seed alfalfa in western Canada (Craig 1983) and an

intermittent pest in canola (both Brassica napus L and B. rapa L) (Wise and Lamb 1998).

Forage alfalfa or alfalfa mixtures are grown on over 4.5 million ha in Canada and less than

30,000 ha are grown for pedigreed seed (Statistics Canada 2001). Harvesting forage alfalfa

keeps lygus bugs from reaching pest status in this crop by reducing their survivorship (Harper

et al. 1990) or increasing their dispersal (Schaber et al. 1990).

Depending on the developmental stage of the lygus bug population, cutting alfalfa for hay

may increase dispersal onto nearby host crops including canola. Many studies in Canada have

documented the species composition and phenology of lygus bugs in alfalfa and canola;

however, these studies did not investigate changes in lygus bug numbers in canola following

harvest of nearby alfalfa. Gerber and Wise (1995) sugested that L. lineolaris first generation

adults may move from plots of seed alfalfa to canola. Timlick et al. (1993) noted that although

alfalfa is an excellent host for lygus bugs, in Manitoba, alfalfa grown for forage is usually cut

by the 3™ week of June when most of the lygus bug population is at the nymphal stage (Gerber

and Wise 1995). Butts and Lamb (1991), in northern and central Alberta suggested that

cruciferous weeds, and not alfalfa, are likely more important sources of lygus bugs colonizing

canola because alfalfa tends to harbour mostly L. borealis, a species that seldom dominates

the pest assemblage in canola (Carcamo et al. 2002). A similar argument was made by Braun

et al. (2001) based on their studies conducted in central Saskatchewan.

The objectives of this study were to (1) compare lygus bug phenological patterns in canola

plots grown adjacent to a seed alfalfa stand and (11) determine if cutting alfalfa for hay resulted

in higher numbers of lygus bugs in canola nearby.

MATERIALS AND METHODS

Lygus activity in canola adjacent to seed alfalfa in Saskatoon

Plots were seeded at the Saskatoon Research Centre farm of Agriculture and Agri-Food

Canada, near Saskatoon, Saskatchewan (Fig. 1) in Ortho Clay Loam soil. Alfalfa, Medicago

officinalis L. cultivar Beaver, was seeded in 1993 in a 0.5 ha solid block at 30 cm row

spacings and at a seeding rate of 2.25 kg/ha. From 1994 to1995, an adjacent 0.5 ha block was

divided into six blocks each consisting of a pair of plots, 8 m wide and 43 m long, planted to

either Brassica rapa (cultivar AC Parkland) or B. napus (cultivar Legend) and separated from

each other by a 1.8 m barrier of barley, Hordeum vulgare L. cultivar Harrington. The location

of each canola cultivar within each of the six blocks was assigned randomly in each replicate

in an overall randomized complete block design. On several occasions in 1993, and weekly

throughout the season in 1994-1995, each canola plot and the adjacent width of alfalfa was

sampled by taking five subsamples of five 180° sweeps using a standard 38 cm diameter insect

net. At the time of sampling, 10 plants per species per replicate were examined and their

growth stage determined according to the scale of Harper and Berkenkamp (1975). Samples

were transferred to plastic bags, returned to the laboratory, and frozen prior to species

determination. Subsamples were averaged to determine the number and species of lygus bug

present per replicate plot.

Lygus abundance in canola adjacent to forage alfalfa

Commercial fields of alfalfa and canola (Brassica napus of unknown varieties) adjacent

to each other or within 50 m were used in the study. Study sites were located at the northern

edge of the Parkland region near Barrhead, Alberta (ca.100 km NW of Edmonton) in 1998-

1999, near Fort St. John in the Boreal ecoregion of British Columbia in 2000, and in the

Southern Parkland region near Carman, Manitoba in 2001 (Fig. 1). Sampling of both crops

began at the late bud or flower stages of canola (3.3-4.1 Harper and Berkenkamp 1975) and

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 a7

Barhead fe TY

Mei ME rc act oh eae

Saskatoon

; ® :

: : = aa 402° 99° 96°

123° 420° 417° «114° 111° 108° 105 |

[pratense ores |

0 100 200 300 km

Figure 1. Location of study sites throughout western Canada used to study lygus bug

abundance in canola adjacent to alfalfa.

continued weekly until one or two weeks after the cutting of alfalfa. To test the hypothesis that

changes in lygus bug numbers in canola were associated with cutting of alfalfa nearby and not

by some other area-wide phenomenon, fields were designated a posteriori as "cut" if the

alfalfa was cut early or "check" if alfalfa was harvested one to two weeks later than the "cut"

fields. Number of paired sites ranged from two to seven at each location and year. Canola

growth stage was determined as described previously; for alfalfa, percent of the stand

flowering or crop height was estimated visually.

Samples of 20 sweeps with a 38 cm sweep net were taken at five positions within each crop

separated by approximately 10 m: at the edge next to the interface and at approximately 20,

40, 60, and 80 m into each crop. In 1998 at Barrhead only three positions and 10 sweeps were

collected at about 10, 20 and 30 m into each crop and at Fort St. John in 2000, 100 sweeps

were taken in subsets of 10 sweeps beginning about 25 m into the stand and at 10 m intervals

from two sites. Sweeping efficiency is expected to differ in alfalfa and canola, particularly

during the pod stages of canola when this crop is difficult to sweep. However, this should not

confound results because our objectives were to compare lygus bug numbers among canola

fields and not between the two crops. All fields were standard commercial size fields greater

than 32 ha. All samples were stored in plastic bags and transferred to 70% ethanol in the lab

for identification to species following the revision by Schwartz and Foottit (1998). Because

only adults are thought to disperse long distances (Schaber et a/. 1990), juveniles were not

always kept from every site or collection and never identified to species.

Data Analysis

The number of weekly samples before and after alfalfa cutting at each canola field varied

from one to three. Therefore, the average number of lygus adults per week in alfalfa before

cutting and in canola before and after alfalfa cutting were calculated for the cut and check

treatments and means were compared using Analysis of Variance (Statistix® for Windows,

version 7). For data with heterogeneous variances, the Kruskal-Wallis non-parametric test was

used.

58 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

RESULTS AND DISCUSSION

Lygus activity in canola adjacent to seed alfalfa

The abundance of lygus bugs was very low in all crops at Saskatoon in 1993 and 1994;

therefore, only the 1995 data are shown. Lygus borealis and L. lineolaris were abundant in

both crops and Lygus elisus was rare (Figs. 2a-c). The first generation adults of L. borealis in

alfalfa peaked in early July and a smaller peak of L. Jineolaris occurred on July 20". Adults

were observed in canola during the early flower stage in early July at the same time as first

generation lygus bug adults peaked in alfalfa. However, alfalfa was not the source because the

alfalfa peak involved L. borealis and the canola peak consisted of L. Jineolaris. This result

supports the observations by Butts and Lamb (1991) and Braun et al. (2001) that at some sites

the two crops are dominated by different species and in such situations alfalfa may not be the

major source of lygus bugs in canola. According to Gerber and Wise (1995), L. lineolaris

populations peak in alfalfa when first generation females become reproductive and move out

of alfalfa to other hosts. Our results, however, support the speculation by Butts and Lamb

(1991) and Braun et a/. (2001) that cutting alfalfa does not increase lygus numbers in canola.

Brassica napus had consistently fewer lygus bugs than B. rapa and alfalfa (Figs. 2b and

c). Lygus bugs moved to canola starting at the bud stage and peaked during flowering. The

higher abundance of lygus bugs in B. rapa than in B. napus was also observed by Butts and

Lamb (1991), and can be attributed to earlier flowering in B. rapa and not to lygus bug feeding

preferences.

Lygus abundance in canola adjacent to forage alfalfa

Lygus lineolaris was the dominant species in canola throughout the study at all sites; L.

borealis was more abundant in alfalfa than canola and was the more common species in this

crop at Barrhead in 1998 and Fort St. John in 2000 (Table 1). Other species such as L. elisus

were rare and L. keltoni was found in small numbers only in Alberta and British Columbia.

There were no significant differences in overall lygus bug abundance or any of the species

between alfalfa fields before cutting (P > 0.05, ANOVA or Kruskal-Wallis test) at any of the

study sites in any year. Therefore, differences in lygus abundance between adjacent canola

after hay harvest were not caused by initial lygus bug numbers in the respective alfalfa fields.

Table 1

Number and percent of total (in parenthesis) of Lygus species at the various study sites.

Alberta 1998 Alberta 1999 B.C. 2000 Manitoba 2001

Lygus species alfalfa canola alfalfa canola alfalfa canola alfalfa canola

L. lineolaris 59 (40) 501 (82) 188(70) 888(85) 94(47) 356(85) 781 (91) 552 (96)

L. borealis 86(58) 101 (17) 66(25) 120(12) 99(50) 54(13) 78(9) — 20(4)

Total lygus adults* 149 610 268 1038 200 419 859 a7

a Sweeps 850 850 1700 3000 900 1100 3300 3200.

* Includes L. keltoni and L. elisus

In 1998 near Barrhead, alfalfa was cut for hay in four of the seven fields between the 18

and 24 of June. Abundance of lygus bugs in the adjacent canola fields did not change when

alfalfa was cut (Fig. 3). In 1998, lygus bug populations reached outbreak levels with over

400,000 ha of canola throughout Alberta sprayed for their control. However, there were

relatively few lygus bugs in the alfalfa fields adjacent to canola in our study sites. This

suggests that alfalfa was not the major source of lygus bugs that colonized canola during the

bud and early flower stages.

In 1999, lygus abundance for individual species or pooled totals were similar between

canola fields adjacent to alfalfa that were cut in early or mid July (Fig. 4, P > 0.05, ANOVA

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 59

30, Alfalfa

20 io.

10) B. rapa

©)

Individuals/5 sweeps

nN =

10, B. napus

r o— 1. borealis adults

e-— {. elisus adults

6 o---- 1. lineolaris adults

a----- Lygus spp. L4-L5 nymphs

4 a—— f ygus spp. L1-L3 nymphs

©)

May Jun Jun Jun Jun Jun Jul Jul Jul Jul Aug Aug Aug Aug Aug

fede 8, 15; 22 30,,7, ,14 20,,27 3 11,18 23 33;

Vegetative Bud Early Mid ~~ Full Pod filling Seeds

Bits Flowering -~--~-- maturing

sampling date (1995)

Figure 2. Lygus phenology at Saskatoon in 1995 in (a) seed alfalfa, (b) Parkland canola, B.

rapa, (c) Legend canola, B. napus. Canola crop stages shown under dates.

60 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

or Kruskal-Wallis tests). Lygus abundance was lower in 1999 than in 1998, and were again

lower in alfalfa than in canola early in the season. This further suggests that most lygus bugs

found in canola came from sources other than alfalfa.

o—— Alfalfa-cut

- e— — Alfalfa-check

= G---- Canola-cut

£ Bon -eeeenss Canola-check

rab)

40]

}

<—

Jun 11 (3.3) Jun 18 (4.1) Jun 24 (4.2) Jul 02 (4.3)

Collection date (1998)

Figure 3. Adult lygus bug abundance in alfalfa and canola near Barrhead in 1998. Entries are

means of 4 fields and 3 fields for the cut and check treatments, respectively + 1 standard error

of the mean. Thirty sweeps were taken per field on each collection date. Numbers in

parentheses are canola crop stages (Harper and Berkenkamp 1975). Arrows indicate period

when alfalfa adjacent to canola was cut.

o— Alfalfa-cut O---- Canola-cut

80, @~— Alfalfa-check = tees Canola-check

i¢2)

@ 60

s ecm ne

o 40 Co eee eg ee bd

rr ae oe i

<— 20 Te ee Ne mm ik Se emt stay : nee

te ae a ey

0 foes

Jun 25 (3.3) Jul 02 (4.1) Jul 07 (4.2) Jul 19 (4.3)

Date sampled (1999)

Figure 4. Adult lygus bug abundance in alfalfa and canola near Barrhead in 1999. Entries are

means of 4 fields for the cut and check treatments +1 standard error of the mean. 100 sweeps

were taken per field on each collection date. Numbers in parentheses are canola crop stages.

Arrows indicate period when alfalfa adjacent to canola was cut.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 61

In 2000, flooding and frost destroyed the fields near Barrhead but two pairs of alfalfa and

canola fields were sampled near Fort St. John (Fig. 5). Lygus bugs have only one generation

per year in this northern agricultural region, therefore, the adults sampled were considered

overwintered adults. It is unknown if these older overwintered adults are as dispersive as the

parous females of the new generation (Stewart and Gaylor 1991, 1994; Gerber & Wise 1995).

At Site 1 (Fig. 5) alfalfa was cut on July 21 and lygus bug adults continued to decrease in the

nearby canola as juvenile numbers increased. The peak in number of overwintered adults in

canola occurred towards the end of June, increasing from about 60 to 100 per 100 sweeps. A

corresponding decrease from 42 to 25 adults per 100 sweeps was observed in the adjacent

alfalfa (Fig. 5). At Site 2 (Fig. 5), alfalfa was cut after July 31 and a very small increase in

abundance of L. lineolaris was observed in the adjacent canola field. The highest count,

however, had occurred on the first sampling date on 7 July. As shown for Field 2 in Fig. 5,

there was already a large number of lygus bug nymphs by the end of July (2 per sweep) at the

time when the alfalfa was cut, indicating that the damaging populations found in canola at the

pod stage had developed within the field. Lygus bug movement to canola from alfalfa or other

hosts at this time was likely to be of little consequence given the large number of juveniles

already present in canola.

Alfalfa Canola

Site 1

500

400 o—— L. lineolaris

nt e—— L. borealis

300 | a O---- Juveniles

200 se) “ p

100 ra a

2 : {

EO $= t= gp a

= Jun Jun Jul Jul Aug Aug Jun Jun Jul Jul Aug Aug

oO 26 830 BAT) one4 4 18 26 8630 14 21 4 18

S (2.6) (3.1) (4.1) (4.3) (5.1) (5.2)

a Site 2

D 250

fia

+ 200 Oo

Jun Jul Jul Jul Jul Jul Aug Aug

26 7 17 7 We, 31 14 22

(4.1) (4.2) (44) (5.2) (5.2)

Date sampled (2000)

Figure 5. Lygus bugs in canola and alfalfa near Fort St. John, B.C. in 2000. Entries are total

bugs caught in 100 sweeps per field at each sampling date. Numbers in parentheses are canola

crop stages. Arrows indicate approximate date alfalfa was cut.

62 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

In 2001 only sites in Manitoba were sampled. Lygus bug population dynamics prior to July

10 were not studied because of late planting of canola and delayed plant growth. The

abundance of either Lygus species or combined lygus bug abundance was the same between

alfalfa fields prior to cutting it on the second week of August, or between the corresponding

canola fields prior to alfalfa hay harvest (P > 0.05, ANOVA). On August 14-16 and August

22-23, after alfalfa was cut, weekly averages of lygus abundance was higher in canola adjacent

to uncut alfalfa than in canola adjacent to cut alfalfa (Fig. 6, F= 111.51, df= 1.5, P< 0.01).

Average weekly numbers of lygus bugs in canola adjacent to cut alfalfa were the same before

and after cutting (17 vs 8 per 100 sweeps from July 10 to August 8 and from August 14 to

August 23, respectively, ANOVA, P > 0.05). In canola fields adjacent to uncut alfalfa, the

average weekly catches for these same periods were 11 and 53 lygus bugs per 100 sweeps (F=

23.7, d.f.= 1.2, P< 0.05). The results from Manitoba in 2001 suggest that cutting of alfalfa

between August 9 and August 13 failed to result in movement "en masse" of lygus bugs from

alfalfa to canola. Therefore, the risk of lygus bug damage in canola at early pod stage was not

affected by cutting the adjacent alfalfa stand.

2 Alfalfa-cut m

YD e— — Alfalfa-check /

. O---- Canola-cut /

= 1001, Sr Canola-check «

~ /

= 50

—_I

Jul Jul Jul Jul-31 to Aug Aug Aug Aug Sept

10-12 17-19 23 Aug-O2 7-8 14-16 22-23 29-30 5

(3.3) (4.1) (42) (44) (1) (52) (5.3)

Period sampled (2001)

Figure 6. Lygus bug adults near Carman, Manitoba in 2001. Entries are averages for 1 to 5

fields depending on availability and access. One hundred sweeps were collected at each site

on each sampling date. Asterisks indicate dates with significant differences between canola

fields adjacent to cut and uncut alfalfa.

Because nymphs were not collected rigorously for the Manitoba portion of the study, it is

not possible to determine if the large number of lygus adults found in canola adjacent to uncut

forage alfalfa moved to canola as adults or developed within the canola stand from nymphs.

It is unlikely that lygus bugs would move to canola at the pod stage since the plants may no

longer be attractive (Butts and Lamb 1991). Instead, in August, lygus bugs may move to more

succulent hosts to feed in preparation for the winter.

Based on the observations from sites in the Parkland and Boreal eco-regions of the prairies

we conclude that cutting alfalfa in these regions does not result in massive movement of adult

lygus bugs into nearby canola. These results cannot be generalized to more southern regions

such as the short grass prairie of Alberta where a different species assemblage occurs and

lygus bugs have 2 or 3 generations. Mark-recapture studies or molecular DNA investigations

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 63

are needed to assess the relative importance of various spring hosts as sources of lygus bugs

that may reach pest status in canola in the summer.

ACKNOWLEDGEMENTS

We thank C.. Verbeek, A. Macaulay, C. Swinarchuk and K. Clarck for field help; C. Herle,

A. Nemecz and K. Gardner for processing and identifying samples; K. Grams and E. Cadieu

for text and graphics support and B. Beres for reviewing a draft of this article. This work was

funded through the abase programs of Agriculture and Agri-Food Canada, Alberta Agriculture

Food and Rural Development and Manitoba Agriculture and Food.

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Braun, L., M. Erlandson, D. Baldwin, J. Soroka, P. Mason, R. Foottit and D. Hegedus. 2001. Seasonal

occurrence, species composition, and parasitism of Lygus spp. (Hemiptera: Miridae) in alfalfa, canola, and

mustard. The Canadian Entomologist 133: 565-578.

Butts, R.A. and R.J. Lamb. 1991. Seasonal abundance of three Lygus species (Heteroptera: Miridae) in oilseed

rape and alfalfa in Alberta. Journal of Economic Entomology 84: 450-456.

Carcamo, H.A., J. Otani, C. Herle, M. Dolinski, L. Dosdall, P. Mason, R. Butts, L. Kaminski and O. Olferrt.

2002. Variation of Lygus (Hemiptera: Miridae) species assemblages in canola agroecosystems in relation

to ecoregion and crop stage. The Canadian Entomologist 134: 97-111.

Craig, C.H.1983. Seasonal occurrence of Lygus spp. (Heteroptera: Miridae) on alfalfa in Saskatchewan. The

Canadian Entomologist 115: 329-331.

Gerber, G.H. and I.L. Wise. 1995. Seasonal occurrence and number of generations of Lygus lineolaris and L.

borealis (Heteroptera: Miridae) in southern Manitoba. The Canadian Entomologist 127: 543-559.

Harper, F.R. and B. Berkenkamp. 1975. Revised growth stage key for Brassica campestris and B. napus.

Canadian Journal of Plant Science 55: 657.

Harper, A.M., B.D. Schaber, T.P. Story and T. Entz. 1990. Effect of swathing and clear-cutting alfalfa on insect

populations in southern Alberta. Journal of Economic Entomology 83: 2050-2057.

Schaber, B.D., A.M. Harper and T. Entz. 1990. Effects of swathing alfalfa for hay on insect dispersal. Journal

of Economic Entomology 83: 2427-2433.

Schwartz, M.D. and R.G. Foottit 1998. Revision of the Nearctic species of the genus Lygus Hahn, with a review

of the Palaearctic species (Heteroptera: Miridae). Memoirs on Entomology, International 10, Associated

Publishers, Gainesville, FL, USA.

Statistics Canada 2001. Census of Agriculture. http://www.statcan.ca/english/Pgdb/econ100a.htm.

Statistix for Windows. 2000. Statistix 7 User’s Manual. Analytical Software, Tallahassee, FL

Stewart, D.D. and M.J. Gaylor. 1991. Age, sex and reproductive status of the tarnished plant bug (Heteroptera:

Miridae). Environmental Entomology 20: 1387-1392.

Stewart, D.D. and M.J. Gaylor. 1994. Effects of age, sex and reproductive status on flight of the tarnished plant

bug (Heteroptera: Miridae). Environmental Entomology 23: 30-84.

Timlick, B.H., W.J. Turnock and I. Wise. 1993. Distribution and abundance of Lygus spp. (Heteroptera: Miridae)

on alfalfa and canola in Manitoba. The Canadian Entomologist 125: 1033-1041.

Wise, I.L. and R.J. Lamb. 1998. Economic threshold for plant bugs, Lygus spp. (Heteroptera: Miridae), in canola.

The Canadian Entomologist 130: 825 — 836.

Young, O.P. 1986. Host plants of the tarnished plant bug, Lygus lineolaris (Heteroptera: Miridae). Annals of the

Entomological Society of America 79: 747-762.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 65

Influence of Trap Colour on the Capture of Codling Moth

(Lepidoptera: Tortricidae), Honeybees, and Non-target Flies

ALAN L. KNIGHT and EUGENE MILICZKY

YAKIMA AGRICULTURAL RESEARCH LABORATORY, AGRICULTURAL RESEARCH

SERVICE, USDA, 5230 KONNOWAC PASS RD., WAPATO, WA 98951

ABSTRACT

Studies were conducted to evaluate the influence of trap colour on the captures of

honeybees, Apis mellifera L., codling moth, Cydia pomonella L., and non target

muscoid flies in sticky delta traps. Traps varied widely in their spectral reflectance. The

unpainted white and the painted white and cream traps had the highest reflectance. The

painted green trap had the lowest total reflectance. The green, orange, and red traps had

low reflectance at wavelengths < 560 nm. Red and green painted traps consistently

caught the fewest honeybees, while the unpainted white trap caught the most. Red

painted traps caught the greatest number of flies. Significantly more codling moths were

caught in green and orange versus the unpainted white traps. In a later experiment,

painted green traps caught more codling moths than unpainted white traps.

Key words: Colour, traps, apple, codling moth, honeybees, muscoid flies

INTRODUCTION

Optimizing trap design is vital in developing a useful monitoring system for codling

moth, Cydia pomonella L. (Knight and Christianson 1999). The effectiveness of a variety

of sticky and non-sticky trap types have been reported (Knodel and Agnello 1990, Vincent

et al. 1990), but until recently, a sticky cardboard white or cream color wing trap has been

the standard for monitoring codling moth in the western United States (Ried| et a/. 1986).

Knight et al. (2002), however, found that either a delta or diamond-shaped trap was more

effective than the standard wing trap in laboratory flight tunnel and in field trials. We

believe the delta-shaped trap has now become the most widely used trap for monitoring

codling moth in Washington State. Unfortunately, early in the season the delta-shaped trap

constructed from white corrugated plastic consistently catches non-target flies and

honeybees, Apis mellifera L. Trap contamination by flies and honeybees requires that the

trap’s sticky liner be replaced more frequently and thus adds to the costs of monitoring

codling moth.

Colour is an important factor influencing the foraging behaviour of honeybees (von

Frisch 1967). Honeybees can differentiate six colour ranges between 300 and 650 nm, Le.

ultraviolet to yellow light (Burkhardt 1964). Variable degrees of contamination of

monitoring traps by honeybees and bumblebees Bombus spp., due to differences in trap

colour have been reported (Hamilton et al. 1971, Gross and Carpenter 1991, Meagher

2001). In general, white and yellow traps are attractive and green traps are unattractive to

Apoidea species due to their differences in spectral reflectance between 380 and 550 nm

(Mitchell et a/. 1989).

The influence of trap colour on the capture of some noctuid pests in sex pheromone-

baited traps has been well studied (McLaughlin et al. 1975, Mitchell et al. 1989).

However, the importance of the visual stimuli provided by traps in these two studies of

night-flying moths contrasted sharply. McLaughlin et al. (1975) found that traps with low

spectral reflectance were more effective in capturing 7richoplusia ni (Hiibner) and

Pseudoplusia includens (Walker), while Mitchell et al. (1989) found that such traps were

66 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2603

less effective with Anticarsia gemmatalis Hibner and Spodoptera frugiperda (J.E. Smith).

Trap colour has not previously been reported to be a specific factor influencing the capture

of codling moth. The objective of our study was to evaluate the influence of trap colour on

the attractiveness and selectivity of delta-shaped traps for codling moth, honeybees, and

non-target flies.

MATERIALS AND METHODS

Description of traps. White delta traps (Suterra, Bend, OR) were left unpainted or

painted with one of five high gloss paints (Krylon , Cleveland, OH): Spring Grass green

#2327, Pumpkin orange gloss #2411, Banner Red Gloss #2108, Ivory gloss #1504, and

Gloss white #1501. The three darker colours were characterized based on value, chroma,

and hue (Munsell Book of Colour 1976): green (4, 8, 5G), red (4, 14, 5R), and orange (6,

14, 2.5YR).

Spectral Reflectance. Trap samples (100 cm’) were scanned with a Perkin-Elmer

Lambda-9/19 spectrophotometer (Wellesley, MA) by Avian Technologies (Wilmington,

OH). Trap surfaces were scanned at wavelengths from 360 to 830 nm with a

monochromatic slit width set at 2 nm and operated at a scan rate of 120 nm/ min.

Experiments 1 and 2. Two experiments were conducted in a 5-year-old ‘Red

Delicious’ apple orchard, Malus domestica (Borkh), (mean (SE) tree height = 2.2 (0.2) m)

situated 15 km east of Moxee, Washington (46°40’N, 120°05’W) at the U.S.D.A.

Experimental Farm during 2003. This orchard was situated 0.6 km east of a large dairy

farm. Bloom in the apple blocks at the farm occurred from 25 April — 15 May. In the first

study (24 — 28 April) delta traps were not baited with a sex pheromone lure. Traps in the

second study (5 — 12 May) were baited with the Biolure 10X codling moth lure (Suterra,

Bend, OR). Ten traps of each colour were placed in a completely randomized design in

each experiment. Unsexed, laboratory-reared codling moth adults (n = 5,000) were

released into the orchard prior to the start of experiment 2 only.

Experiment 3. A third experiment was conducted to compare the attractiveness of the

unpainted white and the green-painted delta traps for codling moth. This study was

conducted in a 10-ha 30-year-old mixed block of ‘Red Delicious’ and ‘Golden Delicious’

situated 5 km north of Moxee, Washington (46°33’N, 120°23’W). Mean (SE) tree height in

this orchard was 4.3 (0.2) m. Six traps of each colour were placed in a completely

randomized design, checked every 2 to 4 d, and re-randomized. Six replicates of this

experiment were conducted from 9 — 26 September. Unsexed, laboratory-reared codling

moth adults (n = 5,000) were released into the orchard prior to the start of the experiment.

In all experiments, the numbers of codling moths, honeybees, and muscoid flies were

counted in each trap. The predominant weather patterns during these tests were clear skies

with maximum daily temperatures ranging from 20 — 32 °C.

Statistical analyses. Data were transformed with square root (x + 0.01) prior to

analysis. Data from experiments 1 and 2 were analyzed with one-way analysis of variance

(ANOVA). The September study was analyzed with a repeated measures design

(ANOVA) across five dates. Means were separated in significant ANOVA’s with Fisher’s

least significance difference (Analytical Software 2001).

RESULTS

The spectral reflectance pattern of delta traps differed sharply among colours (Fig. 1).

The unpainted white and the painted white and cream traps were similar exhibiting > 75%

reflectance at all wavelengths > 420 nm (Fig. 1). These traps had identical reflectance in

the ultraviolet at 5 — 30%. Green traps had the lowest total reflectance among colours

tested with a peak reflectance (ca. 20%) at 520 nm and < 10% reflectance at wavelengths <

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 67

480 nm and > 570 nm (until 810 nm). The reflectance of the orange and red traps increased

rapidly at 560 nm and 600 nm and reached a plateau of ca. 55% at 620 nm and 640 nm,

respectively.

UV! Visible Light : IR

80 4g pewewScae we eS ee = =o rc]

S White ices ===

Percent Reflectance

= se - 2.— s e— ee ePe Pe ere ee lcrrlcrererl eel el eee

360 400 440 480 520 560 600 640 680 720 760 = 800

Wavelength (nm)

Figure 1. Percent reflectance from 360 to 830 nm of six corrugated plastic delta-shaped

traps either left unpainted (white) or painted cream, red, green or orange.

Significant differences were found in the mean capture of codling moths, honeybees

and flies in all but one delta trap comparison in experiments 1 and 2 (Table 1). The fewest

honeybees were caught in the red, orange, and green painted delta traps in experiment 1

and in the painted white, cream, red, and green traps in experiment 2. The painted white

and cream traps caught significantly fewer honeybees than the unpainted white trap in

experiment 1. All but the unpainted white trap caught significantly fewer honeybees than

the orange trap in experiment 2.

The vast majority of flies caught during experiments 1 and 2 were the lesser stable fly,

Muscina stabulans (Fallen), and the little house fly, Fannia canicularis L., likely

immigrating from the nearby dairy. Red traps caught significantly more flies than all other

colours, and orange traps caught significantly more flies than the cream, white, and

Table 1.

The influence of trap colour on the capture of codling moths, honeybees, and flies in delta

traps placed in an apple orchard in experiments 1 (28 April) and 2 (12 May).

Mean (SE) catch per trap

Codling Honeybees Flies

Painted trap moth

colour Exp. 2 Exp. | Exp. 2 Exp: 1 Exp. 2

Unpainted, white 7.7 (2.5)e 9.5(1.2)a 4.4(0.7)a 0.1 (0.1)c 4.9 (1.0)

White 6.0 (1.6)c 2.3(0.5)b 0.6(0.2)c 0.0 (0.0)c 11.3 (4.5)

Cream 14.2 (3.6)be 2.8(0.4)b 0.9(0.5)c 0.3 (0.2)c 5.9 (2.6)

Red 14.8(3.5)abe 0.0 0.0)c_~—-0.0 (0.0) c 3.7 (0.7)a 23.3 (5.2)

Orange 29.8 (7.8)ab 0.3(0.2)c 2.4(0.7)b 1.8 (0.6)b 10.1 (1.6)

Green 34.9 (11.5)a 0.1(0.1)¢ 0.0(0.0)c 1.0 (0.3)bc 8.4 (1.8)

Statistical analysis F=4.24 F= 42.11 F = 15.69 F= 12.58 F= 1.26

df=5, 54 P<0.01 P< 0.0001 P< 0.0001 P< 0.0001 P=0.30

Means within the same column followed by the same letter are not significantly different

at P< 0.05 (LSD test).

68 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

unpainted traps in experiment 1. Fly captures were much higher and more variable during

experiment 2, though no differences were significant (Table 1).

No codling moths were caught in the unbaited traps in experiment 1. Significant

differences in the catch of codling moths in experiment 2 occurred among trap colours

(Table 1). The lowest mean catches were in the unpainted and white traps but these were

not significantly different from the cream and red traps. Catch was significantly higher in

the orange versus the white or unpainted traps. Mean moth catch in the green traps was

significantly greater than in the unpainted, white or cream traps.

The green delta trap caught significantly more codling moths than the unpainted white

trap (F = 42.64; df = 1, 10; P < 0.001); mean (SE) = 13.7 (2.4) versus 6.3 (1.2),

respectively) in experiment 3. No honeybees were caught in any trap in experiment 3, and

the capture of flies was low, averaging < 0.2 per trap, so data were not analyzed.

DISCUSSION

Visual cues are known to be an important factor affecting the close range orientation of

male codling moth to females or synthetic lures (Castrovillo and Cardé 1980). Visual cues

may also play a role in oviposition behaviour, which occurs from late afternoon to dusk

(Ried] and Loher 1980). The role of colour on the orientation of male codling moths at

dusk to discrete sex pheromone sources is unknown. The correlation of our traps’

reflectance data and their relative capture of codling moth suggest that traps with low

reflectance at wavelengths < 560 nm may catch more moths than the standard white and

cream traps. A spectral analysis of the sensitivity of codling moth’s compound eye may

allow us to make a significant improvement in the design of a more effective monitoring

trap.

It is not clear from the literature whether visual detection of a trap by a moth should

increase or decrease the number of individuals captured in a sex pheromone-baited trap.

For example, the compound eyes of some noctuid moths have been shown to have a

bimodal sensitivity to light with peaks in the UV (350 — 370 nm) and green (500 — 575

nm) regions (Agee 1973, Mitchell et al. 1989). Yet, other noctuid species respond more

strongly to traps emitting low spectral reflectance in these regions (McLaughlin et al.

1975).

The significant differences found in the effectiveness of delta traps of different colours

in the capture of codling moths suggest that the potential influence of colour in previous

codling moth trapping studies should be reexamined. Most of the paper and plastic traps

used to monitor codling moth have been cream or white (Riedl et a/. 1986). No studies

with codling moth have compared traps of similar geometry that differ only in colour.

Plastic bucket traps with a green flat top and a white cylindrical bottom were found to have

higher seasonal catches of codling moth than paper, cream colour wing traps (Vincent et

al. 1990). Knodel and Agnello (1990) found that a small, orange delta trap caught nearly

twice as many codling moths as either the cream colour or white wing traps in their study.

Conversely, they also reported that the all-green bucket trap caught fewer moths than any

other design including two designs of a green and white bucket trap. However, these

differences among the bucket traps could have been due to the significant differences in

the size and geometry of the various traps’ openings.

Green delta traps in our studies appeared to be the most selective and attractive colour

for monitoring codling moth. Painted or unpainted white traps and cream traps all caught

honeybees. We did not determine if red, orange or green traps differ in their attractiveness

for codling moth. However, green and red appeared to catch somewhat fewer honeybees

than orange traps, and both green and orange caught fewer flies than red traps.

The benefit derived by excluding honeybees from codling moth traps could be

cancelled by an increase in the trap’s captures of large flies in some orchards. The capture

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 69

of flies varied widely among our experiments due to differences in location and

seasonality. The highest numbers of flies were caught in experiment 2 in an orchard

situated near a dairy, and only negligible captures of flies occurred in experiment 3 in an

orchard surrounded by other orchards. The higher counts of flies in experiment 2 versus

experiment 1 were likely due to an increase in the mean maximum temperatures (> 3 °C)

that occurred from late April to early May.

Visual stimuli are well known to be important factors affecting the behaviour of

muscoid flies (McCann and Arnett 1972). The influence of colour on the level of

attractiveness to the stable fly, Stomoxys calcitrans L., has been shown to be red > green >

yellow > white (Muniz and Hecht 1968). The behavioural responses of S. calcitrans; the

face fly, Musca autumnalis De Geer; and the horn fly, Haematobia irritans L., are all

greatest to surfaces with < 20% reflectance in the range from 350 to 450 nm (Agee and

Patterson 1983). Similarly, in our study the low captures of muscoid flies in the white and

cream traps may be associated with their high mean reflectance (> 50%) in the range from

360 — 450 nm (Fig. 1). Thus it might be possible to reduce the capture of muscoid flies in

the green, red, and orange traps if a UV reflector was added to the trap’s surface.

The congregation of muscoid flies to surfaces can also be their response to regulate

their body temperature (Bushman and Patterson 1981). Flies may congregate on warmer

surfaces during cool mornings or afternoons (Agee and Patterson 1983). The interior

surface of the darker delta traps during the summer can be 2 — 4% warmer than white traps

(unpublished data). Further research detailing the influence of temperature and other

climatic factors on the capture of muscoid flies in delta traps may allow us to further

improve the selectivity of this trap in monitoring codling moth. Further studies on the

visual sensitivity of codling moth and its associated behaviour may allow us to develop a

trap that is both more attractive for codling moth and less attractive to muscoid flies.

ACKNOWLEDGEMENTS

We would like to thank Brad Christianson and Duane Larson, USDA, ARS, Wapato,

WA for their help in setting up the field trials, and Dr. Tom Larson (Suterra, Bend, OR) for

providing the traps. Jim Hansen, USDA, ARS, Wapato, WA and Rick Hilton, Oregon

State University, Medford, OR provided helpful reviews. This research was partially

funded by the Washington Tree Fruit Research Commission, Wenatchee, WA.

REFERENCES

Agee, H.R. 1973. Spectral sensitivity of the compound eyes of field-collected adult bollworms and

tobacco budworms. Annals of the Entomological Society of America 66: 613-615.:°

Agee, H.R. and R.S. Patterson. 1983. Spectral sensitivity of stable, face, and horn flies and behavioural

responses of stable flies to visual traps (Diptera; Muscidae). Environmental Entomology 12: 1823-

1828.

Analytical Software. 2001. Statistix 7, Tallahassee, FL.

Burkhardt, D. 1964. Colour discrimination in insects. Advances in Insect Physiology 2: 131-174.

Bushman, L.L. and R.S. patterson. 1981. Assembly, mating, and thermoregulatory behavior of stable flies

under field conditions. Environmental Entomology 10: 16-21.

Castrovillo, P.J. and R.T. Cardé. 1980. Male codling moth (Laspeyresia pomonella) orientation to visual

cues in the presence of pheromone and sequences of courtship behaviours. Annals of the

Entomological Society of America 73: 100-105.

Frisch, K. von. 1967. The dance language and orientation of bees. L.E. Chadwick, trans]. Belknap Press,

Harvard University, Cambridge, MA.

Gross, H.R. and J.E. Carpenter. 1991. Role of the fall armyworm (Lepidoptera: Noctuidae) pheromone and

other factors in the capture of bumblebees (Hymenoptera: Apidae) by universal moth traps.

Environmental Entomology 20: 377-381.

Hamilton, D.W., P.H. Schwartz, B.G. Townshend, and C.W. Jester. 1971. Effect of colour and design of

traps on captures of Japanese beetles and bumblebees. Journal of Economic Entomology 64: 430-432.

70 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Knight, A. and B. Christianson. 1999. Using traps and lures in pheromone-treated orchards. Good Fruit

Grower 50: 45-51.

Knight, A.L., D. Larson, and B. Christianson. 2002. Flight tunnel and field evaluations of sticky traps for

monitoring codling moth (Lepidoptera: Tortricidae) in sex pheromone-treated orchards. Journal of the

Entomological Society of British Columbia 99: 107-116.

Knodel, J.J. and A.M. Agnello. 1990. Field comparison of nonsticky and sticky pheromone traps for

monitoring fruit pests in western New York. Journal of Economic Entomology 83: 197-204.

McCann, G.D. and D.W. Arnett. 1972. Spectral and polarization sensitivity of the dipteran visual system.

Journal of Insect Physiology 59: 534-558.

McLaughlin, J.R., J.-E. Brogdon, H.R. Agee, and E.R. Mitchell. 1975. Effect of trap colour on captures of

male cabbage loopers and soybean loopers in double-cone pheromone traps. Journal of the Georgia

Entomological Society 10: 174-179.

Meagher, R.L. 2001. Collection of fall armyworm (Lepidoptera: Noctuidae) adults and nontarget

hymenoptera in different coloured unitraps. Florida Entomologist 84: 77-82.

Mitchell, E.R., H.R. Agee, and R.R. Heath. 1989. Influence of pheromone trap colour and design on

capture of male velvetbean caterpillar and fall armyworm moths (Lepidoptera: Noctuidae). Journal of

Chemical Ecology 15: 1775-1784.

Muniz R. and O. Hecht. 1968. Observations on the distribution of the stable fly, Stomoxys calcitrans, on a

small farm and trial on selection of coloured surfaces in free air. Annals of the National Center of

Biology, Mexico 17: 225-243. Munsell Book of Colour. 1976. Munsell colour, Baltimore, MD.

Riedl, H. and W. Loher. 1980. Circadian control of oviposition in the codling moth, Laspeyresia

pomonella, Lepidoptera: Olethreutidae. Entomologia Experimentalis et Applicata 27: 38-49.

Riedl, H., J.F. Howell, P.S. McNally, and P.H. Westigard. 1986. Codling moth management: use and

standardization of pheromone trapping systems. University of California Division of Agriculture and

Natural Resources, Bulletin 1918, Oakland, CA.

Vincent, C., M. Mailloux, E.A.C. Hagley, W.H. Reissig, W.M. Coli, and T.A. Hosmer. 1990. Monitoring

the codling moth (Lepidoptera: Olethreutidae) and the obliquebanded leafroller (Lepidoptera:

Tortricidae) with sticky and nonsticky traps. Journal of Economic Entomology 83: 434-440.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 7h!

Testing an attracticide hollow fibre formulation for control

of Codling Moth, Cydia pomonella

(Lepidoptera: Tortricidae)

ALAN L. KNIGHT

YAKIMA AGRICULTURAL RESEARCH LABORATORY, AGRICULTURAL RESEARCH

SERVICE, USDA. 5230 KONNOWAC PASS RD., WAPATO, WA 98951

ABSTRACT

Laboratory and field tests were conducted to evaluate the use of an experimental

sprayable formulation of chopped hollow fibres loaded with codlemone and mixed with

1.0% esfenvalerate and an adhesive to control codling moth, Cydia pomonella (L.)

(Lepidoptera: Tortricidae). Moths were not repelled by the addition of the insecticide to

the adhesive and were rapidly killed following bref contact. A significantly greater

proportion of male moths flew upwind and contacted individual fibres for a longer

period of time when fibres had been aged > 7 d versus fibres 0 — 7 days-old in flight

tunnel tests. Field tests using sentinel fibres placed in 10.0 mg drops of adhesive on

plastic disks stapled to the tree found that fibres were not touched until they had aged >

8 d. Conversely, moth mortality following a 3-s exposure to field-collected fibres

deposited on the top of leaves was low in bioassays with fibres aged > 8 d. The

deposition and adhesion of fibres within the apple canopy appear to be two major

factors influencing the success of this approach. Fibres were found adhering to foliage,

fruit, and bark within the orchard; however, visual recovery of fibres following each of

the three applications was < 5.0%. Both the substrate and the positioning of the fibre on

the substrate influenced fibre retention. The highest proportion of fibres was found

initially on the upper surface of leaves and this position also had the highest level of

fibre retention. Fibres on the underside of leaves or partially hanging off of a substrate

were dislodged within two weeks.

Key words: sex pheromone, codling moth, attracticide, apple

INTRODUCTION

A variety of approaches have been developed that utilize the sex pheromone of codling

moth, Cydia pomonella L., for its effective management in deciduous tree fruit and nut

crops, including the application of hand applied dispensers (Charmillot and Pasquier

1992), sprayable microencapsulated materials (Charmillot and Pasquier 2001), widely-

spaced aerosol emitters (Shorey and Gebers 1996), and paste droplets formulated with

insecticides (Charmillot et a/. 2000). Chopped hollow fibres loaded with codlemone have

been used for codling moth both in hand-applied formulations (Cardé et a/. 1977) and ina

sprayable formulation in which the fibres were mixed with an adhesive (Moffitt and

Westigard 1984). Fibres provided high levels of disruption throughout the season in these

studies.

Hollow fibres have been widely used in aerial applications in cotton for management of

pink bollworm, Pectinophora gossyptella (Saunders) (Baker et al. 1990). Cotton growers

combined the use of the hollow fibres and synthetic pyrethroids to develop an attracticide

formulation (Beasley and Henneberry 1984). Studies with pink bollworm showed that this

attracticide approach had minimal effect on natural enemies (Butler and Las 1983) and had

significant lethal and sublethal effects, which reduced the pest population (Floyd and

72 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Crowder 1981). This attracticide approach has not been tested with codling moth. Herein

are presented preliminary studies that evaluated the potential of this approach and the use

of chopped fibres for communication disruption of codling moth.

MATERIALS AND METHODS

Laboratory test protocol. The response of male codling moths to an experimental

formulation of black hollow Celcon fibres (200 wm i.d. x 15 mm) loaded with 15%

codlemone diluted in hexane (Scentry Inc., Buckeye, AZ) was observed in a flight tunnel.

Fibres were formulated to release 0.1 g/h codlemone at 20 °C (Weatherston et al. 1985).

The tunnel was 1.65 m long, 0.56 m wide and 0.56 m high and constructed from 6 mm

thick acrylic sheeting. A blower was used to push air within the room (maintained at 22 —

24 °C and 50 — 60% RH) into a plenum, through a charcoal filter, and through a series of

screens before passing into the working section of the tunnel. An identical blower was

used on the opposite end to pull air through the tunnel. Power to the blowers was provided

by two 12-volt battery chargers attached to 115-volt AC variable resistors. By carefully

adjusting the speed of each blower, laminar airflow was created which passed through the

tunnel at the rate of 0.13 m/sec (measured by movement of smoke). Exhaust was expelled

to the outside of the building. Red lights installed above the working section of the tunnel

provided enough light (4.3 lux) to make observations.

Insects were obtained as mature larvae inside corrugated cardboard strips from a

laboratory colony reared on a soybean diet at the Yakima USDA Insectary (Toba and

Howell 1991). Virgin male moths were collected daily and conditioned in constant light

for 24 — 48 h at 21 °C and 60% RH. Prior to testing, moths were placed in complete

darkness for 30 min.

Technical esfenvalerate (Dupont Agricultural Products, Wilmington, DE) was diluted

in acetone and mixed with adhesive at a 1.0% wt/wt concentration. A single hollow fibre

was placed on a 10.0 mg droplet of a polybutene adhesive (Biotac 100, Scentry

Biologicals, Billings, MT) in the center of an 18.0 mm diameter plastic disk. The plastic

disk with the fibre was placed on a small metal platform suspended 30 cm from the top of

the flight tunnel at the air inlet end. Moths were released from a 30 cm high platform

placed near the air outlet end of the tunnel. The number and duration of individual visits

to the fibre were recorded for 7 min with an infrared motion detector coupled to a

computer.

Attractiveness and toxicity of laboratory-aged fibers. Two types of tests were

conducted in the flight tunnel to assess the attractiveness of individual fibres for male

codling moths and the toxicity and possible repellency of adding an insecticide to the

adhesive. In the first test, hollow fibres were aged for 7 d at 24 °C prior to testing. Ten

replicates of 10 moths were flown to a fibre placed either in adhesive or in adhesive with

insecticide. Treatments were run alternately for each replicate, n = 10. The attractiveness

and toxicity of fibres placed on adhesive treated with 1.0% esfenvalerate and aged in a

greenhouse were evaluated in the second test. Disks were collected after 0, 1, 4, 7, 14, 21,

and 28 d and kept frozen at —10 °C. Five fibres from each age class were tested in the flight

tunnel in a random order and each fibre was tested twice, n = 10 replicates. Six males

were released simultaneously for each fibre and allowed to fly for 7 min. Moths were

collected individually in vials at the end of each flight test and mortality was scored after

24 hat 24 °C.

Field test protocol. Field studies of fibres were conducted in 1992 and 2003. Three

applications of fibres were made to a 0.3 ha (214 trees) 5-year-old ‘Golden Delicious’

block trained on a M-16 rootstock with central leader architecture on 5 May, 1 June, and

28 July 1992. The mean (SE) height of trees was 2.1 (0.1) m. A standard spinning cone

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 Te

applicator used for ground application of the fibre in field crops (Moffitt and Short 1982)

was supplied by Scentry personnel and attached to a tractor. The tractor and sprayer were

calibrated to deliver 100.0 g of fibres (15.0 g a.i.) in 6.0 L adhesive per hectare. The

deposition and retention of fibres were evaluated following an application on 9 July 2003

in a 4.0-ha orchard of mixed apple cultivars. The orchard was treated with 250.0 g of a

10.0% a.i. fibre mixed with 4.7 L adhesive per hectare using a specialized tractor-pulled

overhead applicator (Blue Line Manufacturing, Wenatchee, WA). The same adhesive and

fibre were used in both years.

Attractiveness and toxicity of field-aged fibres. The attractiveness and toxicity of

field-aged fibres were evaluated throughout the 1992 season. On each of the three spray

dates one fibre was placed on a 10.0 mg adhesive drop in the center of each of 120 plastic

disks that were stapled to the wooden posts of a wire deer fence situated > 50 m from the

apple orchard. On each subsequent sampling date 10 disks without any moth scales were

placed in the upper third of the apple orchard’s canopy in a horizontal position. These

sentinel fibres were left in the orchard for 5 — 7 d and then reexamined with a microscope

for the presence of moth scales. In addition, on each sampling date 10 fibres deposited by

the spray application on the upper surface of leaves were collected from the orchard and

returned to the laboratory. Five 1 — 2 d-old chilled laboratory-reared moths were touched

to each fibre using a suction hose for 3 s. Moth mortality was scored after 24 h at 24 °C.

Deposition and retention of fibres. Several studies were conducted during the season

to assess the deposition and retention of fibres in the apple orchard. A trial was conducted

on 12 September to estimate the number of fibres applied per hectare. Blank white celcon

fibres (200 ym i.d. x 15 mm) were mixed with the adhesive and applied at the standard rate

(100.0 g in 6.0 liters adhesive). Five dark blue tarps (2.92 m x 2.92 m) were placed in a

row on a grassy strip. The sprayer was started 50 m away from the first tarp and once

fibres had begun to be released from the spinning cone the tractor was driven forward at a

speed of 4.0 km per h. The number of fibres deposited on each sheet was counted and used

to estimate the number of fibres applied to the entire orchard (area equivalent to 426 tarps).

Deposition of fibres within the canopy of the orchard was estimated following each spray

application by visually examining 60 trees for fibres. Individual trees were inspected for 3

to 5 minutes from the ground. The retention of marked fibres within the canopy of the

apple orchard was evaluated following the June application in 1992. Fifty-seven fibres

were located on leaves and their location was marked with flagging. The retention of these

fibres was checked after 2 and 7 wk.

One hundred and twenty-two fibres were located and marked with flagging one day

after the application in 2003. The position of each fibre was recorded with respect to

substrate and whether the fibre was in full contact with the substrate or if a portion of the

fibre was detached from the substrate (overhanging). Their retention in the canopy was

subsequently evaluated on 14 and 21 July and 22 August.

Statistical analyses. An unpaired t-test and analysis of variance on transformed data

(square root [x+0.01]) were used to compare the attractiveness and toxicity of fibres placed

in adhesive either with or without insecticide and to fibres aged from 0 — 28 d to cohorts of

moths, respectively (Analytical Software 2000). Means in significant ANOVA’s were

separated with Fisher’s LSD test, P< 0.05.

RESULTS

Attractiveness and toxicity of laboratory-aged fibers. No difference was found in

the number of moth visits to fibres placed in either clean (mean + SE = 13.4 + 1.7) or

insecticide-impregnated (17.4 + 2.3) adhesive during the 7-minute bioassay in the flight

tunnel (t = 1.40, df = 18, P = 0.18). Similarly, no difference was found in the duration of a

moth visit between fibres placed in clean (1.9 + 0.5) or insecticide-impregnated adhesive

74 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

(1.8 + 0.4) (t = -0.09, df = 18, P = 0.93). Subsequent tests showed that the age of the fibre

was a Significant factor affecting moth contact and moth mortality (Table 1). Fibres placed

in insecticide-impregnated adhesive and aged for < 7 d had significantly fewer moth

contacts and reduced visitation time. No difference in either factor was found for fibres

aged 14 — 28 d. A significantly greater proportion of moths per cohort were killed when

flown to fibres aged 14 - 28 d versus < 1 d-old fibres. The highest moth mortality occurred

with fibres aged 14 d (Table 1). The lack of a significant difference in moth mortality

following exposure to fibres aged 4 — 7 d versus 21 — 28 d may have been due to a decline

in the toxicity of the insecticide in the older drops.

Table 1

Influence of age on the attractiveness and toxicity of an individual hollow fibre loaded

with 15% codlemone and placed on a 10.0 mg drop of adhesive treated with 1.0%

esfenvalerate for male codling moths flown in a flight tunnel.

Mean (SE)

Mean (SE) # of Mean (SE) time (s) proportion of dead

Age of fibre (d)* contacts” per source contact . moths‘

0 2.4 (0.9)c 0.3 (2.1)b 0.29 (0.04)c

1 1.4 (0.7) c 0.2 (0.1)b 0.20 (0.05) c

4 1.9 (1.0) c 0.1 (0.03) b 0.50 (0.09) be

4 5.7 (1.4) be 0.3(0.1)b 0.49 (0.05)bc

14 16.8 (3.5) a 1.4(0.3)a 0.88 (0.04)a

21 11.8 (2.6) ab 0.9 (0.2) ab 0.68 (0.12) ab

28 19.1 (5.8) a 1.4 (0.5)a 0.67 (0.10) ab

Statistical analysis F=6.82;df=6,63, F=3.93;df=6, 46; F = 9.82: df = 6, 46;

P<0.0001 P<0.01 P<0.001

“Fibres were aged in a greenhouse maintained between 20 — 24 °C for up to 28 days.

Ten cohorts of six moths were flown in the flight tunnel for 7 minutes for each fibre age

class. The mean number of moth contacts and time per source visit per cohort were

measured with an infrared motion detector hooked to a computer.

“ Following each tests moths which contacted adhesive were collected and placed

individually in vials. Mortality was scored after 24 h at 24 °C.

Attractiveness and toxicity of field-aged fibres. No moth scales were found on the

sentinel fibres placed in the apple orchard during the first eight days after any of the three

applications (Table 2). The proportion of fibres aged from 8 — 51 d visited by moths

ranged from 0.43 — 0.85 during the season. Mortality of moths in the 3-s touch bioassay

was > 85% for fibres collected on the day of the spray application. In general, fibres were

initially sticky and associated with several milligrams of adhesive. Moth mortality

dropped sharply with field aging of the fibres, however, 65 — 80% mortality occurred with

8 d and 5 d old fibres after the second and first applications, respectively. Moth mortality

was much lower with 7 d-old fibres following the third application (Table 2). Moth

mortality with field-collected fibres collected 2 — 7 wk after the application ranged from

0.0 — 30.0%.

Deposition and retention of fibres. The mean (SE) number of fibres counted per tarp

was 32.9 (15.3). Extrapolating the deposition of fibres on the tarps to the area of the entire

orchard (equivalent to 426 tarps) estimated 14,015 fibres were applied. Following the 5

May spray application a mean (SE) of 0.9 (0.3) fibres were sampled per tree. This first

application was made a few days past full bloom and the growth of green foliage was

limited. The mean density of fibres following the 1 June application when trees had

abundant foliage increased to 2.5 (0.4) fibres per tree. However, fibre density following the

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 75

third application on 28 July was somewhat lower, 1.5 (0.4) fibres per tree. The highest

density of fibres found on a single tree during the season was 17. Extrapolating the mean

density of fibres sampled per tree (1.5 — 2.5) multiplied by the number of trees in the block

(214) suggests that only 2.3 — 3.8% of the estimated number of fibres sprayed in the

orchard (14,015) were deposited on the trees.

Table 2

Proportion of sentinel hollow fibres placed in 10 mg adhesive on a plastic disk at various

times following a spray application that contained moth scales and moth mortality

following a 3-s touch to field-aged fibres deposited on the upper surface of apple leaves.

Post-spray interval Proportion of fibres % moth mortality in

Date checked (d) fibre was in field touched * touch bioassay Z

5 May 0 -- 100.0

10 May 1-5 0.00 80.0

17 May 5-12 0.85 22.0

1 June 0 -- 96.0

9 June 2-8 0.00 65.0

16 June 8-15 0.45 30.0

23 June [5-22 0.85 10.0

30 June 22229 0.60 12.0

7 July 29 - 36 0.40 18.0

14 July 36 - 43 0.55 6.0

22 July 43-51 0.40 0.0

28 July 0 -- 86.0

4 August 1-7 0.00 26.0

11 August 7-14 0.75 14.0

19 August 14-22 0.43 8.0

* Positive visitation of codling moth to sentinel fibres was based on the microscopic

detection of moth scales in the adhesive surrounding each sentinel fibre. Fibres and

adhesive were placed in the center of plastic disks that were stapled horizontally in the

upper third of the tree canopy and left in the field for 5 — 7 d.

* Moth mortality was assessed 24 h following a 3 s touch exposure to a field-collected fibre

on the upper surface of a leaf. Five moths were tested per fibre and ten fibres were

collected on each date.

Table 3

Retention of hollow fibres loaded with codlemone and mixed with an adhesive in the

canopy of an apple orchard following a spray application on 9 July 2003.

% fibres lost after

Position of fibre # fibres 4d lld 43d

Top of leaf 52 9.6 17.3 25.0

Top of leaf, overhanging 19 36.8 84.2 100.0

Bottom of leaf 9 55.6 55.6 100.0

Bottom of leaf, overhanging 16 68.8 75.0 100.0

Fruit 21 28.6 47.6 61.9

Bark 5 20.0 40.0 80.0

Total 122 28.7 49.2 59.8

76 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Retention of fibres on apple trees was short-lived. Following the 1 June application in

1992, < 50% of marked fibres on leaves were retained on trees after 2 wk and

approximately 10% were retained after 7 wk. The 2003 study showed that the retention of

fibres is variable based on differences in their location and alignment on various substrates

(Table 3). Following the 9 July application 58% of fibres were located on the top of leaves.

Deposition of fibres on the bottom of leaves and on fruit was similar with about 20% each.

Fibres deposited on the trunk and branches of trees accounted for < 5% of the total. A

large proportion of fibres deposited initially on leaves were found overhanging the edge of

the leaf. This was more common for fibres deposited on the underside of leaves with 64%

of fibres overhanging. Retention of fibres was highest on the top of leaves with fruit being

the second best. Fibres overhanging on leaves and all fibres deposited on the underside of

leaves were lost within 43 d. In comparison, 60% and 80% of the fibres deposited on fruit

and bark were loss within 6 wk, respectively. Only a quarter of the fibres deposited on the

top of leaves and not overhanging were lost.

DISCUSSION

The experimental formulation of hollow fibres loaded with codlemone and mixed with

an insecticide in this study was ineffective as an attracticide due to several factors

including the emission rate of the fibre and the toxicity of the adhesive. The initial

emission rate of codlemone from individual fibres was apparently too high to allow moth

contact. Fibres had to be aged for > 7 d before male codling moths would contact fibres

under both flight tunnel and field conditions. Moth mortality was high following brief

contact with newly applied fibres but dropped rapidly with time. Modifications are needed

to improve the performance of this attracticide approach.

The emission characteristics of sex pheromones from hollow fibres are well studied

(Ashare et al. 1982). Fibres typically have an initial high release and then have a lower and

fairly constant rate over an extended period of time. Previous studies with hollow fibres

loaded with codlemone have shown that fibres can be long lived. Cardé et al. (1977)

reported complete shutdown of lure-baited traps for 10 wk. Moffitt and Westigard (1984)

reapplied fibres every 4 — 5 wk during the season. The emission rate of hollow fibres can

be adjusted by modifying either the internal diameter of the fibre or by changing the length

of the fibre (Ashare et al. 1982). Modifications of these factors could likely improve the

use of fibres as an attracticide for codling moth.

Proper choice of an adhesive is critical in developing an effective attracticide. The

viscosity of the adhesive affects both the application and the adhesion of the fibres. The

polybutene adhesive Biotac has been widely used with hollow fibres (Beasley and

Henneberry 1984, Moffitt and Westigard 1984) and is available in several formulations

that differ in their viscosity and are appropriate for the range of temperatures experienced

from early spring to late summer. Yet, fibres were generally associated with limited

amounts of adhesive, < 1.0 mg; and were often poorly attached to the plant. In contrast,

the initial laboratory studies placed fibres on large 10.0 mg drops of adhesive. This limited

amount of adhesive associated with fibres under field conditions formed a dry film that

was not effective in transferring a toxic dose of insecticide to codling moth adults. In

comparison, the large drop of Biotac was toxic for several weeks in laboratory bioassays.

The use of non-drying grease or a different type of adhesive instead of Biotac might extend

the toxicity of the insecticide under field conditions.

Future improvements of the attracticide method for codling moth could include the use

of a more concentrated insecticide dose. A 1.0% sticker formulation with permethrin and

fenvalerate did not cause mortality of P. gossypiella while a 10.0% concentration was

effective (Haynes and Baker 1986). Yet, formulations with only 0.1% concentrations of

cyfluthrin killed 100% of codling moths when formulated in a castor oil-based paste (Lésel

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 77

et al. 2000). One attract and kill paste formulation currently registered for control of

codling moth contains 6.0% permethrin (Charmillot et al. 2000). These paste formulations

remain effective against codling moth for at least 6 wk (Charmillot et a/. 2000, Lésel et al

2000).

The impacts of, an attracticide approach can include both lethal and sublethal effects

such as the interference with mate location by males (Haynes and Baker 1986). While

sublethal effects were not examined in our field studies, previous flight tunnel tests with

codling moth found significant effects on male flight behaviours with concentrations of

esfenvalerate as low as 0.04% (unpublished data). Further studies that can characterize the

sublethal effects of the range of attracticide formulations for codling moth would be

useful.

Depositing more fibres in the canopy would improve the effectiveness of this

formulation both as an attracticide and for mating disruption of codling moth. The

application methods used to apply fibres have included specialized and expensive ground

and air equipment (Moffitt and Short 1982). Results reported here suggest that this

approach is ineffective in placing a significant number of hollow fibres in the tree canopy.

Fibres deposited in the apple tree canopy were primarily deposited in the middle of the

upper leaf surface. This fibre position also appeared to be the most stable over time with

nearly 75% of fibres retained after 6 wk. Unfortunately, the adhesion of fibres to bark or

the underside of leaves was low and short-lived. Increasing the number of fibres sprayed

per hectare is one approach that could be used to increase the density of deposited fibres.

Ground applications in orchards with larger trees or denser canopies or perhaps the use of

aerial applications might improve the deposition rates of hollow fibres and needs to be

further examined.

ACKNOWLEDGEMENTS

I would like to thank John Turner (U.S.D.A., A.R.S., Yakima, WA) for his help in

conducting the field studies and Tom Weissling (University of Nebraska, Lincoln, NE) for

his help in conducting the statistical analysis. Rick Hilton, Oregon State University,

Eugene Miliczky, USDA, ARS, Wapato, WA, and Peter Shearer, Rutgers University,

Princeton, NJ provided helpful reviews. This project received partial funding from the

Washington Tree Fruit Research Commission, Wenatchee, WA.

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F. Kydonieus and M. Beroza (eds.), Insect suppression with controlled release pheromone systems,

Volume 2. CRC Press, Boca Raton, FL.

Baker, T.C., R.T. Staten, and H.M. Flint. 1990. Use of pink bollworm pheromone in the southwestern

United States, pp. 412-436. In R.L. Ridgway, R.M. Silverstein, and M.N. Inscoe (eds.), Behaviour-

modifying chemicals for insect management. Marcel Dekker Inc, New York, New York.

Beasley, C.A. and T.J. Henneberry. 1984. Combining gossyplure and insecticides in pink bollworm

control. California Agriculture 38: 22-24.

Butler, G.D. and A.S. Las. 1983. Predaceous insects: effect of adding permethrin to the sticker used in

gossyplure applications. Journal of Economic Entomology 76: 1448-1451.

Cardé, R.T., T.C. Baker, and P.J. Castrovillo. 1977. Disruption of sexual communication in Laspeyresia

pomonella (codling moth), Grapholitha molesta (oriental fruit moth) and G. prunivora (lesser

appleworm) with hollow fibre attractant sources. Entomologia Experimentalis et Applicata 22: 280-

288.

Charmillot, P.J. and D. Pasquier. 1992. Lutte par confusion contre le carpocapse Cydia pomonella L.

Revue Suisse de viticulture arboriculture horticulture 24: 213-220.

Charmillot, P.J., D. Hofer, and D. Pasquier. 2000. Attract and kill: a new method for control of the

codling moth Cydia pomonella. Entomologia Experimentalis et Applicata 94: 211-216.

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Charmillot, P.J. and D. Pasquier. 2001. Essai préliminaire de lutte par confusion contre la cochylis

Eupoecillia ambiguella et le carpocapse Cydia pomonella au moyen des microcapsules 3M. IOBC

wprs Bulletin 24: 63-64.

Floyd, J.P. and C.A. Crowder. 1981. Sublethal effects of Permethrin on pheromone response and mating of

male pink bollworm moths. Journal of Economic Entomology 74: 634-637.

Haynes, K.F., W.G. Li, and T.C. Baker. 1986. Control of pink bollworm moth (Lepidoptera: Gelechiidae)

with insecticides and pheromones (Attracticide): lethal and sublethal effects. Journal of Economic

Entomology 79: 1466-1471.

Losel, P.M., G. Penners, R.P.J. Potting, D. Ebbinghaus, A. Elbert, and J. Scherkenbeck. 2000. Laboratory

and field experiments towards the development of an attract and kill strategy for the control of the

codling moth, Cydia pomonella. Entomologia Experimentalis et Applicata 95: 39-46.

Moffitt, H.R. and R.E. Short. 1982. A ground mechanism for dispensing insect pheromones to fruit trees.

United States Department of Agriculture, Agricultural Research Service Report AAT-W-22.

Moffitt, H.R. and P.H. Westigard. 1984. Suppression of the codling moth (Lepidoptera: Tortricidae)

population on pears in southern Oregon through mating disruption with sex pheromone. Journal of

Economic Entomology 77: 1513-1519.

Shorey, H.H. and R.G. Gerber. 1996. Use of puffers for disruption of sex pheromone communication of

codling moths (Lepidoptera: Tortricidae) in walnut orchards. Environmental Entomology 25: 1398-

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J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 19

Numbers and types of arthropods overwintering on common

mullein, Verbascum thapsus L. (Scrophulariaceae), in a

central Washington fruit-growing region

DAVID R. HORTON and TAMERA M. LEWIS

USDA-ARS, 5230 KONNOWAC PASS Rd., WAPATO, WA, UNITED STATES 98951

ABSTRACT

Densities and types of arthropods overwintering on common mullein, Verbascum thapsus

L., in a fruit-growing region of Central Washington were determined. Over 45,000

arthropods were collected from 55 plants (5 plants from each of 11 sites), dominated

numerically by Acari and Thysanoptera. Insects representing 8 orders and 29 families were

identified, distributed both in the basal leaf rosettes and in the stalk material of the plants.

One specialist insect herbivore of mullein, the mullein thnps, Haplothrips verbasci

(Osborn), was abundant at all sites. Several pest and predatory taxa that commonly occur

in orchards were also collected, suggesting that mullein may be a source of overwintered

pests or predators moving into orchards in early spring. Pest taxa included primarily

western flower thrips (Frankliniella occidentalis (Pergande)), Lygus spp., and tetranychid

spider mites. Common predators included phytosetid mites and minute pirate bugs (Orius

tristicolor (White)). Sites that were geographically close to one another were not more

similar (in taxonomic composition of overwintering arthropods) than more distantly

separated sites.

Key words: common mullein, overwintering, orchard pests, predatory arthropods, mullein

thrips, western flower thrips, Orius tristicolor, mites

INTRODUCTION

Common mullein, Verbascum thapsus L. (Scrophulariaceae), is a biennial herb native to

Eurasia (Munz 1959) but now common throughout North America. The species occurs in

open waste areas, along fence lines, in overgrazed pastures, and along river bottoms, often

found growing in large single-species stands. Common mullein has a biennial life cycle,

germinating from seed often near clunips of the dead parental plants. In the first year, the plant

develops as a rosette of soft, bluish-gray leaves which are densely covered with silky hairs.

The following year, a stout, leafy stalk is sent up from the center of the rosette, often reaching

a height of more than 2 m in mid-summer. At the top of the stalk is a spike having 100-200

yellow flowers which are in bloom several at a time for much of the summer.

There is a great deal of interest in managing or conserving non-agricultural habitats

adjacent to agricultural habitats to enhance biological control or to reduce infestation of crops

by pest species (Pickett and Bugg 1998; Ekbom ef al. 2000). In Pacific Northwest fruit

growing regions, common mullein often is abundant on the perimeter of pome and stonefruit

orchards. The plant 1s known to harbor important pests of tree fruits during the growing season

(Thistlewood et al. 1990; Krupke et al. 2001), but it also is an important source of certain

predators (e.g., Campylomma verbasci (Meyer), the mullein bug) that may provide biological

control of aphids and mites during the growing season. Less information is available

concerning use of mullein by pests and predators as an overwintering habitat (McAtee 1924).

It is important to understand late winter and early spring population dynamics of pests and

predators in pear and apple orchards, as that time of year is often crucial for pest control.

Thus, we need also to understand the overwintering biology of arthropods both inside and

outside of the orchard, including a determination of where pests and predators overwinter

80 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

(Horton and Lewis 2000; Horton et al. 2002).

McAtee (1924), in Maryland, conducted a cursory survey of the insects associating with

common mullein, and found that the dense basal rosette of leaves provided overwintering

habitat for several taxa of arthropods, including both pest and predatory insects. Thus, in

addition to being a source of pest and beneficial arthropods during the summer and fall

growing season, common mullein may also be a source of overwintered arthropods moving

into Central Washington orchards in late winter and early spring. Objectives of the present

study were to determine types and densities of arthropods overwintering on common mullein

in a fruit-growing region of Central Washington. The study was designed to provide a more

thorough look at the arthropod communities in mullein than provided by McAtee (1924), and

to provide data for a western US population of mullein. We also compared types and numbers

of arthropods overwintering in the basal rosette of leaves to numbers and types occurring in

the leaves, dried flowers, and seed capsules of the stalk. Lastly, we looked for geographic

patterns in the taxonomic composition of arthropod communities overwintering in mullein,

testing the hypothesis that arthropod communities would be more similar between sites that

occur geographically near one another than between sites that were more widely separated.

MATERIALS AND METHODS

The study was done in and adjacent to Yakima, Washington, USA. Eleven sites, each

having stands of fully mature common mullein, were selected in November 2000 for sampling.

Plants that were sampled had bloomed the previous summer and were composed of dead

leaves and seed-laden stalks at the time of collection. All of the sites were along roadsides that

occurred immediately adjacent to orchard habitat or within 1 km of orchard habitat. Straight-

line distances between sites ranged between 0.5 to 46.4 km. In December 2000 and January

2001, we collected five fully mature plants (1.5 to 1.8 m tall) from each site by cutting the

plants just beneath the soil surface. Plants were placed in large plastic bags for transport to

the laboratory. Bags and plants were placed in a large walk-in cooler (2 °C) until the

arthropods were extracted. To extract the arthropods, the plant material was distributed among

25 Berlese-Tullgren funnels (Southwood 1980), keeping stalks and leaf rosettes separate. We

used 40 watt light bulbs to force the arthropods into 75% ethanol.

Arthropods were then separated from the plant detritus by first slowly pouring the alcohol

through very fine (0.2 x 0.2 mm) organdy mesh. The mesh appeared to capture all but the very

smallest mites (mostly immature Tydeidae and Tenuipalpidae). These specimens were

discarded without being identified, thus summaries provided below for Acari underestimate

total numbers of certain small-bodied taxa. The arthropods remaining on the mesh were

removed from the mesh and plant detritus with forceps, insect pins, or small paint brushes, and

transferred to fresh 75% ethanol for later counting and identification.

Insects other than Lepidoptera (all of which were in the caterpillar stage) and parasitic

Hymenoptera were identified at least to family. Known important predators and pests in

orchards were identified to species. Most samples contained very large numbers of

Thysanoptera, and it was not feasible to identify each specimen. A subsample of 50 thrips was

removed from each sample for identification to genus beneath a dissection microscope, using

the key of Mound and Kibby (1998). Immature thrips were not classified. Results for the

subsample were then extrapolated back to the full sample to provide estimates of total numbers

of thrips for each genus. Representative examples of each genus were sent to an expert in

thrips identification (Steve Nakahara; Beltsville, MD) to confirm our identifications.

Mites were very abundant in the leaf rosettes and much less abundant in the stalk material,

thus we limited acarine identifications to those mites inhabiting the leaf rosettes. The

identifications were confined to six of the 11 sites. We first separated Gamasida from the total

sample, for later examination. From the remaining sample, a subsample of approximately 50

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 81

to 500 mites (depending upon total numbers in the sample) were mounted in Hoyer's solution

on microscope slides (Krantz 1978). The mites were then identified to genus (Tetranychus

spp. only) or to family under a compound microscope using keys in Krantz (1978). Counts

for Tetranychus spp. were then extrapolated back to the total sample to obtain estimates of

absolute densities for Tetranychus spp. From the Gamasida whole sample, subsamples of 25

to 85 mites were then taken for those sites having large numbers of gamasid mites (>90 mites).

The mites were mounted on slides in Hoyer's solution and identified to family (all but

Phytoseiidae) or to species (Phytosetidae). Species identifications for the Phytoseiidae were

made using keys in Schuster and Pritchard (1963) and Chant et al. (1974). We then

extrapolated results for the subsample back to the full Gamasida sample to provide estimates

of absolute numbers for phytoseiid species.

Straight-line distances between sites were obtained using a Vista global positioning unit

(Garmin; Olate, KS). We tested whether sites that were geographically near one another were

more similar than those more distantly separated by calculating taxonomic (family-level)

similarity between all possible site pairs, using the following formula:

Relative absolute distance = > Absolute value [(x;,/ >) — (Xj4/ DE) ,

where j and k are two sites, x, 1s the abundance of the i” insect family at site 7, and x, is

abundance of the i” insect family at site k (Ludwig and Reynolds 1988). The analysis was

limited to families of Insecta. The index varies between 0 and 2, with 0 indicating maximum

similarity and 2 indicating complete dissimilarity between the two sites.

RESULTS

A total of 46,712 arthropods was counted from the 11 sites, of which 44.7% were collected

from the leaf rosettes and the remaining 55.3% were collected from the stalk material. The

samples were dominated numerically by the Thysanoptera and Acari (Table 1), accounting for

over 90% of the arthropods from both leaf and stalk material. For the Insecta, 29 families in

8 orders were identified, with species of Thysanoptera, Coleoptera, and Heteroptera being the

most abundant. There was considerable site-to-site variation in counts (Table 1, Range) for

virtually all common taxa.

Mites were very abundant in the leaf rosettes (exceeding 500 per 5-plant sample) and much

less abundant in the stalk material (Table 1). Specimens from leaf rosettes at six of the 11 sites

were identified, and were found to include large numbers of Gamasida and Actinedida (Table

2). Gamasida were composed primarily of Phytoseiidae, including some important predatory

species (Amblyseius spp.; Typhlodromus caudiglans Schuster; western predatory mite,

Galendromus occidentalis (Nesbitt)). Spider mites (Tetranychidae) were relatively uncommon

(Table 2), and included primarily Tetranychus spp. (47 of 64 tetranychids in subsamples).

Thysanoptera included two families, Thripidae and Phlaeothripidae (Table 1), the latter

apparently being represented by a single species, Haplothrips verbasci (Osborn), the mullein

thrips. This species was very abundant in both stalks and leaf rosettes, reaching densities of

over 800 adults per stalk at one site. Thripidae included species of Thrips (apparently mostly

Thrips tabaci Lindeman but including T. fallaciosus Nakahara), Caliothrips, and Frankliniella

(apparently all western flower thrips, F. occidentalis (Pergande)).

Homoptera were composed primarily of aphids and psyllids (Table 1), including pear

psylla, Cacopsylla pyricola (Foerster), a pest of pears. Heteroptera were dominated

numerically by Anthocoridae and Miridae (Table 1). The 75 Tingidae that were collected all

occurred in the leaf rosettes at a single site. Anthocoridae were almost exclusively minute

pirate bug, Orius tristicolor (White) (164 total specimens), but included also five specimens

of Xylocoris umbrinus Van Duzee. Overwintering Coleoptera were dominated numerically

82 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Table 1

Mean (averaged over 11 sites) numbers of arthropods per 5 mullein plants in leaf rosettes and

stalk material. Numbers 1n parentheses indicate percentage of total arthropods composed of

that taxon [(tr) indicates less than 0.1%]. Range shows minima and maxima across the 11

sites. Family means may not sum to order means due to presence of unidentified arthropods

in that order (particularly true for Thysanoptera, for which immatures were not identified).

Leaf rosettes Stalks

Mean numbers Range (per Mean numbers Range (per

per 5 plants (“%) 5 plants) per 5 plants (“%) 5 plants)

Acari 534.2 (28.1) 123-1455 34.0 (1.4) 3-167

Thysanoptera 1266.9 (66.7) 30-3936 2263.5 (96.5) 210-5516

Thripidae 515.6 0-2362 590.4 49-1655

Phlaeothripidae 710.6 25-1652 1467.5 64-4174

Homoptera 8.0 (0.4) 1-29 4.5 (0.2) 0-22

Aphididae 33 0-14 0.6 0-3

Cercopidae 0.1 0-1 0.0 0

Cicadellidae 0.3 0-1 0.0 0

Psyllidae 4.3 0-14 3.8 0-8

Heteroptera 30.5 (1.6) 4-87 8.9 (0.4) 0-32

Anthocoridae TT 0-22 Tal 0-30

Berytidae 0.1 0-1 0.0 0

Lygaeidae 1.6 0-16 0.0 0

Muiridae 10.6 0-64 0.8 0-6

Nabidae 0.1 0-1 0.0 0

Pentatomidae 0.6 0-2 0.0 0

Reduviidae 0.1 0-1 0.0 0

Rhopalidae 23 0-12 0.1 0-1

Tingidae 6.8 0-75 0.0 0

Coleoptera 35.6 (1.9) 1-169 33.5 (1.4) 6-98

Anthicidae 0.0 0 0.1 0-1

Carabidae 0.2 0-1 0.0 0

Coccinellidae 0.5 0-1 0.0 0

Corylophidae 5.7 0-37 0.6 0-6

Curculionidae 21D 1-130 32.5 6-98

Dermestidae 0.0 0 0.1 0-1

Staphylinidae 0.8 0-3 0.0 0

Neuroptera 0.5 (tr) 0-2 0.1 (tr) 0-1

Hemerobiidae 0.5 0-2 0.1 0-1

Lepidoptera 3.9 (0.2) 0-17 0.3 (tr) 0-2

Diptera 2.7 (0.1) 0-16 0.4 (tr) 0-2

Cecidomyiidae LS 0-11 OD 0-2

Chironomidae 0.2 0-2 0.1 0-1

Mycetophilidae 0.1 0-1 0.0 0

Syrphidae 0.1 0-1 0.0 0

Hymenoptera 10.2 (05) 0-73 0.5 (tr) 0-2

Parasitoids 3.5 0-7 0.5 0-2

Formicidae 6.5 0-69 0.0 0

Vespidae 0.1 0-1 0.0 0

Araneae 7.4 (0.4) 0-21 0.8 (tr) 0-3

Opiliones 0.1 (tr) 0-1 0.0 (tr) 0

Chilopoda 0.2 (tr) 0-1 0.0 (tr) 0

Isopoda 0.1 (tr) 0-1 0.0 (tr)

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 83

Table 2

Taxonomic composition of mite subsamples (Oribatida, Acaridida, Actinedida) and absolute

numbers of Gamasida in mullein leaf rosettes at each of 6 sites.

Site 1 Site 2 Site 3 Site 4 Site 5 Site 6

Oribatida 49 1 5 27 0 1

Acaridida 2 35 5 7 6 1

Actinedida 76 121 55 551 a7 237

Anystidae 53 37 15 3 7 i

Bdellidae 2 14 0 0 0 0

Camerobiidae 10 4 4 0 4 17

Cunaxidae 0 0 1 7 0 0

Raphignathidae 3) 21 11 0 1 0

Smarididae 2 11 0 0 0 0

Tarsonemidae 0 0 0 128 0 0

Tenuipalpidae B) 0 0 0 1 0

Tetranychidae 2 31 13 4 9 5

Tydeidae 1 3 11 409 1 208

Unidentified 0 0 0 0 34 0

Counted but not classified 0 235 90 841 92 364

Gamasida 238 94 58 29 52 379

Ameroselidae O* OF 0 4 0 Q*

Ascidae 1 le 38 2 0 O*

Laelapidae 0* 8* 7 0 0 OF

Phytoseiidae 83% 1 13 23 oa 81*

Unidentified jig |? 0 0 It oiy

* Results for a subsample of mites taken from the Gamasida total.

by an unidentified weevil that appears to be associated with the flowering and seeding mullein

stalk also during the growing season. For the remaining taxa, spiders and ants were fairly

abundant (both exceeding five specimens per 5-plant sample) in the leaf rosettes. Over 90%

of the ants were collected at a single site.

Known tree fruit pests overwintering in mullein included pear psylla, spider mites, western

flower thrips, Lygus hesperus Knight, and Lygus elisus Van Duzee (Table 3). Western flower

thrips was especially abundant in the stalks, where densities reached 1000 thrips per 5- plant

sample. Lygus spp. had a density of over 10 bugs per 5-plant sample overwintering in the leaf

rosettes (Table 3). Beneficial arthropods known to occur in orchards and found overwintering

in mullein included primarily phytoseiid mites and minute pirate bugs (Table 3), with much

lower numbers of a few other species. Phytoseiidae included species of Typhlodromus, G.

occidentalis, and unidentified Amblyseius. Minute pirate bugs were common, having a density

of almost 15 bugs per 5-plant sample.

Taxonomic similarity (based upon insect families) between sites showed no relationship

with distance between sites (Fig.1).

DISCUSSION

A large and diverse community of arthropods used both the leaf rosettes and stalks of

common mullein as overwintering habitat. The communities were dominated numerically by

Thysanoptera (leaves and stalks) and Acari (leaves), but other taxa including Heteroptera and

Coleoptera were also relatively common. At certain sites, insects and mites overwintering in

mullein easily exceeded a density of 1000 arthropods per plant, numbers considerably larger

84 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

Table 3

Mean densities (averaged over 11 or 6 [Acari] sites) of arthropods found overwintering in

mullein that are also known pest or natural enemy inhabitants of orchards. Densities expressed

as numbers per 5 mullein plants. Mites not identified for stalk samples.

Leaf

rosettes Stalks

ORCHARD PESTS

Acari Tetranychidae 25.8 --

Tetranychus (urticae group') 19.0 --

Thysanoptera Frankliniella occidentalis 280.0 733.4

Homoptera Cacopsylla pyricola 3.5 3.6

Heteroptera Lygus spp. 10.5 0.6

ORCHARD BENEFICIALS

Acari Phytosei1idae 124.0 --

Galendromus occidentalis” 106.5 --

Typhlodromus spp.” 11.3 --

Amblyseius spp.” 6.2 --

Heteroptera Orius tristicolor Vie?! del

Deraeocoris brevis (Uhler) 0.1 0.2

Geocoris spp. 0.6 0.0

Coleoptera Stethorus picipes Casey 0.2 0.0

'Mean density estimated by extrapolating from subsamples (Table 2); spider mites were

identified using keys in Baker and Tuttle 1994.

* Mean density estimated by extrapolating from subsamples.

* Mean density estimated by extrapolating from subsamples of Gamasida (Table 2).

than those reported by McAtee (1924) in Maryland (who appears to have ignored Acari and

Thysanoptera in his brief study). It is of interest that a plant native to Eurasia would host such

substantial numbers of phytophagous arthropods in North America. However, several of the

most common species that we collected are cosmopolitan or Holarctic in distribution,

including western flower thrips and mullein thrips, and it is likely that these species have

geographic ranges in Europe and Asia that overlap the native range of common mullein.

Indeed, the mullein thrips is known to specialize on species of Verbascum in Europe and North

America (Bailey 1939). Bailey records this thrips as overwintering both in the leaf rosette and

in the seed capsules or stalk material of V. thapsus, as shown also here.

The western flower thrips was very abundant overwintering in mullein (Table 3),

suggesting that this plant may be an important source of flower thrips moving into orchards

during early spring. Western flower thrips is a major source of early season damage on

nectarines and certain apple varieties in the Pacific Northwest (Madsen and Jack 1966;

Bradley and Mayer 1994; Pearsall and Myers 2000). Pearsall and Myers (2000, 2001)

concluded that location of nectarine orchards in relation to wild habitats strongly affected

early-season densities of thrips in orchards, with those orchards adjacent to other orchards

(rather than adjacent to non-orchard habitats) having the lowest spring densities of thrips.

These authors suggested that certain herbaceous and shrubby plant species in native habitats

of the Pacific Northwest are a source of flower thrips that colonize nectarine orchards.

Pearsall and Myers (2000) did not include common mullein in their list of important plant

species, but results reported here indicate that common mullein should also be considered to

be an important source of western flower thrips in tree fruit growing regions of the Pacific

Northwest.

Other potential pests of tree fruits, including pear psylla, Lygus spp., and spider mites,

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 85

were present in mullein but at considerably lower densities than flower thrips. Pear psylla is

known to overwinter in a variety of locations outside of the pear orchard (Kaloostian 1970).

Lygus spp. are sporadic pests in pear, apple, and stone fruit crops (Beers et al. 1993).

Common mullein has been reported to be a host plant of Lygus lineolaris (Palisot de Beauvois)

in eastern North.America (Young 1986), but it is not clear whether the two species recovered

in the present study (L. hesperus and L. elisus) use mullein as more than overwintering habitat.

McAtee (1924) recorded that Lygus sp. overwintered on common mullein leaf rosettes in

Maryland. Spider mites are often abundant on broad-leaf plants within and adjacent to

orchards, and these plants appear to be sources of pest mites moving into fruit trees during the

summer (Flexner et al. 1991; Alston 1994; Coli et al. 1994). Our results indicate that common

mullein growing near orchards in the Pacific Northwest may be a source of overwintered

spider mites that could eventually disperse into fruit trees.

Several important predator species also overwintered on common mullein, including the

highly abundant O. tristicolor and predatory mites. Orius tristicolor is an important predator

of thrips, mites, and other small soft-bodied prey (Askari and Stern 1972; Salas-Aguilar and

Ehler 1977). This and other species of Orius are known sources of biological control in

orchards (Westigard et al. 1968; Niemczyk 1978; McCaffrey and Horsburgh 1986), and our

results suggest that mullein could be a source of early spring populations of O. tristicolor in

orchards. McAtee (1924) collected Orius insidiosus (Say) overwintering on common mullein

in Maryland.

Predatory mites were abundant in mullein, and included three genera (Galendromus,

Typhlodromus, Amblyseius) that are common in apple and pear orchards of North America

(McGroarty and Croft 1978; Croft et al. 1990; Horton et al. 2002), where they provide

biological control of pest mites (Hoyt 1969). As with spider mites in orchards, predatory mites

may colonize fruit trees from herbaceous or shrubby vegetation within or adjacent to orchards

(McGroarty and Croft 1978; Johnson and Croft 1981; Alston 1994). Thus, the present study

suggests that common mullein could act as a fairly important source of beneficial mites that

provide biological control of pest mites in Pacific Northwest orchards.

There was substantial variation among sites in densities of arthropods overwintering on

mullein (range: 272 arthropods per plant to 1986 arthropods per plant). Any of several factors

could have contributed to this variation, including host quality, types and amounts of

insecticides used in nearby orchards (e.g., Thistlewood et al. 1990), and local environmental

or microenvironmental conditions. We hypothesized at the beginning of this study that sites

close to one another geographically would tend to have taxonomically similar communities

compared to sites geographically separated. There was no support for this hypothesis (Fig. 1),

possibly due to the fact that two taxa (Thripidae and Phlaeothripidae) were almost invariably

the most numerically dominant taxa at all sites, and comprised more than 80% of all

arthropods collected.

CONCLUSIONS

Both the leaf rosettes and stalks of common mullein provided overwintering habitat to a

large and taxonomically diverse collection of phytophagous and predatory arthropods.

Because this plant species commonly occurs in disturbed habitats adjacent to tree fruit

orchards in the Pacific Northwest, it may be an important source of both pest and beneficial

arthropods colonizing orchards. It is not possible to speculate on whether growers benefit

from having large stands of mullein growing near their orchards, as the potential benefits must

be judged relative to the possible harm caused by pests which overwinter on the plant or use

it as a host during summer. The net effect in an orchard of being adjacent to stands of mullein

would depend, at a minimum, on the numbers of pest and beneficial arthropods overwintering

in the stand (which appears to be highly variable among stands), as well as each species'

86 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

ot ee a

PO © ©

oe)

Oo ff

Relative absolute distance

0 10 20 30 40 50

Distance between sites (km)

Figure 1. Scatter plot showing relationship of relative absolute distance (1.e., taxonomic

similarity) and geographic distance for all possible pairings of sites. Smaller values of relative

absolute distance indicate increasing taxonomic similarity between sites. Analysis limited to

Insecta at family level.

tendency to disperse into orchards. Until we better understand factors affecting overwintering

densities of specific pest and beneficial arthropods, and their post-overwintering movements,

it is impossible to predict whether mullein is beneficial or detrimental for growers.

ACKNOWLEDGEMENTS

We thank Merilee Bayer, Deb Broers, Ivan Campos, Dan Hallauer, and Toni Hinojosa for

field and laboratory assistance. We are also very grateful to Steve Nakahara for assistance in

identifying our samples of thrips. We thank Gary Reed for loaning us his Berlese funnels.

The comments of Rick Redak and Gene Miliczky on an earlier draft of this manuscript are

appreciated. This research was partially supported by the Initiative for Future Agriculture and

Food Systems (USDA-CSREES-IFAFS; award number 00-52103-9657), and by funds

obtained from the Washington State Tree Fruit Research Commission and the Winter Pear

Control Committee.

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Horton, D.R., D.A. Broers, T. Hinojosa, T.M. Lewis, E.R. Miliczky and R.R. Lewis. 2002. Diversity and

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J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 89

SCIENTIFIC NOTE

New Aquatic Beetle Records for Canada

(Coleoptera: Haliplidae, Dytiscidae)

R. D. KENNER

SPENCER ENTOMOLOGICAL MUSEUM, DEPARTMENT OF ZOOLOGY, UNIVERSITY

OF BRITISH COLUMBIA, VANCOUVER, BRITISH COLUMBIA V6T 1Z4

D. J. LARSON

DEPARTMENT OF BIOLOGY, MEMORIAL UNIVERSITY OF NEWFOUNDLAND,

ST. JOHN’S, NEWFOUNDLAND AI1B 3X9

R. E. ROUGHLEY

DEPARTMENT OF ENTOMOLOGY, UNIVERSITY OF MANITOBA,

WINNIPEG, MANITOBA R3T 2N2

ABSTRACT

Three species of aquatic beetle, Peltodytes simplex (LeConte) (Haliplidae), Agabus

oblongulus Fall (Dytiscidae) (both from southern British Columbia) and //ybius oblitus

Sharp (Dytiscidae) (from southern Ontario) are confirmed as members of the Canadian

fauna based on specimens deposited in the Spencer Entomological Museum at the

University of British Columbia.

The most recent checklists for the aquatic beetle fauna of Canada are Larson et al.

(2000) (Dytiscidae) and “Checklist of Beetles of Canada and Alaska” (Bousquet 1991) (all

other families). In order to ensure the accuracy of such lists, it is important that each record

be traceable to an accessible voucher specimen whose identity and provenance can be

verified (McCorquodale 2001, Wheeler 2003).

The collections in the smaller museums found at universities and other institutions

across Canada are a valuable resource for the documentation of Canada’s biodiversity

(Wiggins et al. 1991). These collections are frequently overlooked in taxonomic and

biodiversity studies (McCorquodale 2001). In part, this neglect is due to chronic under-

funding and under-staffing and the lack of authoritative determinations. We have been

reexamining the Hydradephaga in the Spencer Entomological Museum collection

(SMDV), checking the determinations and building a database of specimen information. A

number of interesting records have been found; three in particular stand out and are

reported here.

Peltodytes simplex (LeConte): BC, Jaffray, 16 Jul 1955, G. Stace-Smith, 1 male

(SMDV). Peltodytes simplex was previously known from the southwestern United States

(California, Nevada) and northwestern Mexico (Baja California) (R.E. Roughley,

unpublished). We are unaware of any records for this species from either Washington or

Oregon; there are no records for Utah (Kuehnl 2002). There seems little reason to doubt

the accuracy of the collection data as G. Stace-Smith was a respected collector who

collected prodigiously in British Columbia. This record represents a major northward

range expansion for this species and implies a disjunct distribution. Similar disjunct

distributions are known in other species, however, it is unclear in this case if the gap in the

90 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

distribution is real or an artifact of collecting effort. The current status of P. simplex in

British Columbia is unknown as there appear to be no subsequent records.

Agabus oblongulus Fall: BC, Metchosin (in “fresh” creek behind beach), 1 Apr 1976,

J.D. Reynolds, 1 male (SMDV); BC, Victoria, 13 Feb 1985, B.F. & J.L. Carr, 1 female

(CNCI). This species is very similar to A. punctulatus Aubé and a number of the latter

species labeled as A. oblongulus were found in the SMDV and Canadian National

Collection of Insects (CNCI). The two species are separated by overall shape and by

characters of the male protarsal claws and aedeagi (Larson et al. 2000). Unassociated

females cannot always be identified with confidence. The A. oblongulus specimen in the

SMDV is a male and we are confident of its identity; the CNCI specimen is an

unassociated female so we cannot be as confident of its determination.

Agabus oblongulus may not be a new addition to the Canadian fauna as Criddle (1929)

included it in his summary of new Canadian records for 1928. No voucher specimen for

that record is known and because of the difficulties in correctly determining this species,

such a record cannot be accepted without a voucher specimen. Its inclusion in Larson and

Roughley (1991) is probably based on four specimens in the CNCI collected by H.B.

Leech in Salmon Arm. We reexamined those specimens and found that they are A.

punctulatus not A. oblongulus.

Ilybius oblitus Sharp: ON, Rondeau Provincial Park, 26 Jun 1985, G.G.E. Scudder, 1

female (SMDV). //ybius oblitus has a widespread distribution in the eastern United States

and its occurrence in Canada was expected (Larson et al. 2000). This species is included in

Larson and Roughley (1991). As there are no Canadian specimens of this species in the

CNCI (Y. Bousquet, personal communication), it is possible that its inclusion was based

on the SMDV specimen.

Based on the records reported here, P. simplex needs to be added to the “Checklist of

Beetles of Canada and Alaska” with an entry under BC. The listings for /. oblitus (ON)

and A. oblongulus (BC) are now validated by voucher specimens. Larson et al. (2000)

needs to be amended as follows: J. oblitus (225a) needs to be added to Table 1 with an

entry for ON; the species totals then become 277 for Canada and 160 for ON. The

distribution information in the species discussions needs to be updated for A. oblongulus

and /. oblitus.

We thank Y. Bousquet and A. Davies of the Canadian National Collection for

information and loan of specimens.

REFERENCES

Bousquet, Y. (ed). 1991. Checklist of Beetles of Canada and Alaska. Research Branch, Agriculture Canada

Publication 1861/E.

Criddle, N. 1929. The Entomological Record 1928. Fifty-ninth Annual Report of the Entomological

Society of Ontario, Ontario Department of Agriculture, pp. 110-124.

Kuehnl, K.F. 2002. The Crawling Water Beetles (Haliplidae) of Utah; Taxonomy and Biogeography. MSc.

Thesis, Brigham Young University, Provo, Utah.

Larson, D.J., and R.E. Roughley 1991. Dytiscidae, pp. 62-72. In Y. Bousquet (ed), Checklist of Beetles of

Canada and Alaska. Research Branch, Agriculture Canada Publication 1861/E.

Larson, D.J., Y. Alarie, and R.E. Roughley 2000. Predaceous Diving Beetles (Coleoptera: Dytiscidae) of

the Nearctic Region, with emphasis on the fauna of Canada and Alaska. NRC Research Press, Ottawa,

ON, Canada.

McCorquodale, D.B. 2001. New records and notes on previously reported species of Cerambycidae

(Coleoptera) for Ontario and Canada. Proceedings of the Entomological Society of Ontario, 132: 3-13.

Wheeler T.A. 2003. The role of voucher specimens in validating faunistic and ecological research.

Biological Survey of Canada (Terrestrial Arthropods), Document series No. 9.

Wiggins, G.B., S.A. Marshall, and J.A. Downes 1991. The importance of research collections of terrestrial

arthropods. Bulletin of the Entomological Society of Canada, No. 23, Supplement, pp.1-16.

J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003 91

SCIENTIFIC NOTE

Flight activity of Agriotes lineatus L. and A. obscurus L.

(Coleoptera: Elateridae) in the field.

STEVE CROZIER, ANDREA TANAKA and ROBERT S. VERNON

‘ PACIFIC AGRI-FOOD RESEARCH CENTRE,

AGRICULTURE AND AGRI-FOOD CANADA

The dusky wireworm, Agriotes obscurus L., and the lined click beetle, A. lineatus L.

(Coleoptera: Elateridae) were introduced to British Columbia (BC) from Europe around

1900 (Wilkinson et al. 1976). Their initial discoveries in BC (King 1950; King et al.

1952) and the Maritime provinces (Eidt 1953) were of particular importance at that time,

since both species were considered among Europe’s most destructive insects (Eidt 1953).

In recent years, these species have become major pests of small fruit, vegetable,

ornamental and forage crops throughout the Fraser Valley of BC (Vernon ef a/. 2001).

Since their discovery in Canada, it has been stated that A. /ineatus and A. obscurus

populations do not fly (Eidt 1953; Wilkinson et a/. 1976), although flight activity in both

species has been reported from Europe (Brian 1947). Whether these species actually fly

in Canada is of importance, since the efficacy of various alternative control methods under

consideration (e.g. mass trapping, mating disruption and physical exclusion) would likely

be affected by flight activity. This note describes a number of independent observations

made by the authors under field conditions in the lower Fraser Valley of BC in 2001 and

2002, which verify that flight activity occurs in both A. /ineatus and A. obscurus.

Agassiz, 2001: In a 1 ha fallowed field in Agassiz, BC, a Vernon beetle trap (PheroTech

Inc., Delta, B.C. V4G 1E9) baited with A. obscurus pheromone (Vernon et al. 2001) was

inspected at 1530 on 22 May, 2001. The temperature at that time was 28 °C under sunny

skies with only a slight breeze. The contents of the trap, which consisted of 85 male A.

obscurus, were emptied into an open metal pan for sorting. Although most of the beetles

were dead, a number were still quite active and one beetle climbed onto a film vial in the

pan and took flight. It flew about 3 m to the east, then turned and gained altitude from 1

m to 2 mand flew west, at one point flying about 2.5 m high. The beetle flew for about 30

m at which point it was caught in mid air about 2 m above ground and saved for

identification. The specimen was confirmed as a male A. obscurus (by R. Vernon).

Ladner, 2002: Several click beetles were observed in flight between 1230 and 1530 on 12

May, 2002 in a 1 ha field of pasture surrounded by larger fallow fields in Ladner, BC. The

temperature was 24 °C at 1200 under sunny skies with westerly winds at 13 km/h and a

relative humidity of 64%. The field directly west of the pasture was in the process of

being cultivated, and at least 20 click beetles appeared to be flying toward the pasture from

that direction. A number of the click beetles in flight were captured and tentatively

identified in the field as a mixture of A. lineatus and A. obscurus.

When the thick grass of the pasture was also inspected, large numbers of A. lineatus

and the occasional A. obscurus (about 5 tol0 beetles/m’) were observed crawling up the

blades of grass, raising their elytra and taking flight. Out of 20 beetles captured in flight

by hand, every one was capable of escaping from the captor’s open hand via flight.

Flights were best described as direct and deliberate with little to no side-to-side

movements. Beetles gained altitudes up to 4 m with the majority flying between | and 2 m

in height. The beetles appeared to be relatively strong fliers, travelling at the speed of a

92 J. ENTOMOL. SOC. BRIT. COLUMBIA 100, DECEMBER 2003

brisk jog or approximately 5 tol0 km/h. Distance covered while flying ranged from less

than 1 m to 100 m on one occasion, with an average flight covering a distance of 2 to 3 m.

Twelve beetles were intercepted mid-flight on clothing while traversing the pasture. The

captured specimens were confirmed (by R. Vernon) as A. /ineatus males (6) and females

(2) and A. obscurus males (4).

Flight behaviour was again observed in the field of pasture between 1430 and 1700 on

24 May, 2002. Temperatures ranged from 16-17 °C during this period under scattered

cloud with westerly winds at 7 km/h and relative humidity between 56% and 46%. Flight

activity was not as prevalent as on 12 May, with only eight beetles being observed in

flight. Most flights appeared to occur in random directions within the pasture, with no

beetles being observed to enter into or exit from the surrounding fallow fields. Six beetles

were captured in flight and positively identified (by R. Vernon) as male A. Jineatus (5) and

male A. obscurus (1).

Surrey, 2002: Both male and female A. obscurus and A. lineatus were observed in flight

between 1300 and 1700 on 12 May, 2002 at a suburban residence in South Surrey, British

Columbia. The flight activity coincided with the first warm day of the beetle emergence

period (R.S. Vernon, unpublished data), at a temperature of approximately 26 °C under

sunny skies. Beetles were observed climbing blades of grass on a recently cut lawn.

Successful flight from the grass usually took several attempts and short flights in the range

of 10 cm were common. With longer flights, beetles rose at a constant velocity up and out

of the yard at altitudes of 1 to 4m. A single male A. /ineatus successfully took off from

the lawn, gained an altitude of about 1 m, descended towards a deciduous shrub and

circled a horizontal branch before landing on the upper side. Closer inspection revealed

the presence of an A. Jineatus female 5 cm away. At 1600, an average density of four click

beetles/0.09 m’ of lawn was recorded. Active beetles were found in the house all that day,

but had not been seen the previous day. By around 1700, flight activity had mostly ceased.

Beetles were searched for daily throughout the rest of the summer, but were never

observed in a mass flight again. Of 20 beetles captured in flight, 6 male and 5 female A.

lineatus and 4 male and 5 female A. obscurus were positively identified in the lab (R.

Vernon). Females frozen and dissected later were found to contain eggs in good

condition.

REFERENCES

Brian, M.V. 1947. On the ecology of beetles of the genus Agriotes with special reference to A. obscurus.

Journal of Animal Ecology 16:210-224.

Eidt, D.C. 1953. European wireworms in Canada with particular reference to Nova Scotian infestations.

Canadian Entomologist 85:408-414.

King, K.M. 1950. Vegetable insects of the season 1949 on Vancouver Island. Canadian Insect Pest

Review 28:1-2.

King, K.M., R. Glendenning and A.T.S. Wilkinson. 1952. A wireworm (Agriotes obscurus (L.)).

Canadian Insect Pest Review 30:269-270.

Vernon, R.S., E. Lagasa and H. Philip. 2001. Geographic and temporal distribution ofAgriotes obscurus

and A. lineatus (Coleoptera: Elateridae) in Bntish Columbia and Washington as determined by

pheromone trap surveys. Journal of the Entomological Society of British Columbia 98:257-265.

Wilkinson, A.T.S., D.G. Finlayson and C.J. Campbell. 1976. Controlling the European wireworm

Agriotes obscurus L., in corn in British Columbia. Journal of the Entomological Society of British

Columbia 73:3-5.

NOTICE TO CONTRIBUTORS

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Submit contributions to:

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Kalamalka Forestry Center

3401 Reservoir Road Phone (250) 549-5696

Vernon, BC _ V1B 2C7 Fax (250) 542-2230

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AAA

Journal

of the

Entomological Society

of British Columbia

Volume 100 Issued December 2003 ISSN #007 1-0733 |

Directors of the Entomological Society of British Columbia, 2003-2004

Corbet, P.S. A positive correlation between photoperiod and development rate in summer

species of Odonata could help to make emergence date appropriate to latitude: a

testable hypothesis

Heeley, T., R.I. Alfaro, L. Humble and W.B. Strong. Distribution and life cycle of

Rhyacionia buoliana (Lepidoptera: Tortricidae) in the interior of British Columbia..19

Maclauchlan, L.E., L. Harder, J.H. Borden and J.E. Brooks. Impact of the western balsam

bark beetle, Dryocoetes confusus Swaine (Coleoptera: Scolytidae), at the Sicamous

Creek research site, and the potential for semiochemical based management in

alternative silviculture systems

Gillespie, D.R., R:G. Foottit, J. L. Shipp, M.D. Schwartz, D.M.J. Quiring, and Kaihong

Wang. Diversity, distribution and phenology of Lygus species (Hemiptera: Miridae)

in relation to vegetable greenhouses in the lower Fraser Valley, British Columbia, and

southwestern Ontario

Carcamo, H.A., J. Otani, J. Gavloski, M. Dolinski and J. Soroka. Abundance of Lygus

spp. (Heteroptera:Miridae) in canola adjacent to forage and seed alfalfa

Knight, A.L. and E. Miliczky. Influence of Trap Colour on the Capture of Codling

Moth (Lepidoptera: Tortricidae), Honeybees, and Non-target Flies

Knight, A.L. Testing an attracticide hollow fibre formulation for control of Codling

Moth, Cydia pomonella (Lepidoptera: Tortricidae)

Horton, D.R. and T.M. Lewis. Numbers and types of arthropods overwintering on

common mullein, Verbascum thapsus L. (Scrophulariaceae), in a central Washington

fruit-growing region

SCIENTIFIC NOTES

Kenner, R.D., D.J. Larson and R.E. Roughley. New Aquatic Beetle Records for Canada

(Coleoptera: Haliplidae, Dytiscidae)

Crozier, S., A. Tanaka and R.S. Vernon. Flight activity of Agriotes lineatus L. and A.

obscurus L. (Coleoptera: Elateridae) in the field

NOTICE TO CONTRIBUTORS