es Journal of the

Entomological Society of British Columbia

Volume 108 Issued December 201 1 ISSN #0071-0733

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COVER: Torymus azureus (Hymenoptera: Torymidae)

This 3-mm wasp is drilling with her ovipositor into a developing spruce cone which has been infested by the galling midge Kaltenbachiola rachiphaga (Diptera: Cecidomyiidae). Her larvae will parasitize the midge larvae, providing a measure of biological control against the cecidomyiid.

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Journal of the Entomological Society of British Columbia

Volume 108 Issued December 2011 ISSN #0071-0733

Directors of the Entomological Society of British Columbia, 2011-2012... 2

L. Camelo, T.B. Adams, P.J. Landolt, R.S. Zack and C. Smithhisler. Seasonal patterns of capture of Helicoverpa zea (Boddie) and Heliothis phloxiphaga (Grote and Robinson) (Lepidoptera: Noctuidae) in pheromone traps in Washington State.......... 3

E. Miliczky and D.R. Horton. Occurrence of the Western Flower Thrips, Frankliniella occidentalis, and potential predators on host plants in near-orchard habitats of Washington and Oregon (Thysanoptera: Thripidae).............cccccccceessseeceeessteeeeeesnsees |

G.G.E. Scudder, L.M. Humble and T. Loh. Drymus brunneus (Sahlberg) (Hemiptera: Rhyparochromidae): a seed bug introduced into North America................cccccceeees 29

A.G. Wheeler, Jr. and E.R. Hoebeke. Asciodema obsoleta (Hemiptera: Miridae): New Records for British Columbia and First U.S. Record of an Adventive Plant Bug of Scotch Broom (Cyisus sconarius; Fabaceae) j.2cceceeesccetersesns ceccevieextorcenshcaracecernse> 34


W.G. van Herk and R.S. Vernon. Mortality of Metarhizium anisopliae infected wireworms (Coleoptera: Elateridae) and feeding on wheat seedlings is affected by VAC MVE Wiel O Ils sasentaststacaadsesseaastennnatacnaavoncats iecssnnee ren iat teteaea aes Mia teat atct anatase coe ae 38


Symposium Abstracts: Invasion Biology! Douglas College, New Westminster, B.C., RCs Ta OU cance gt ae AE th a eee ce recente tan reat ocd ye cham ene stee 42

Entomological Society of British Columbia Annual General Meeting Presentation Abstracts. University of the Fraser Valley, Abbotsford, B.C., Oct. 14, 2011............ 44

NOTICE TO THE CONTRIBUTORS. ....00.......ecccccceceeeeeeteeeees Inside Back Cover



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Seasonal patterns of capture of Helicoverpa zea (Boddie) and Heliothis phloxiphaga (Grote and Robinson) (Lepidoptera: Noctuidae) in pheromone traps in Washington State.



In each of the 6 years of this study in south central Washington state, male corn earworm moths, Helicoverpa zea (Boddie), first appeared in pheromone traps in late May to mid June, and thereafter were present nearly continuously until mid to late October. Maximum numbers of male corn earworm moths captured in pheromone traps occurred in August and early September. Male Heliothis phloxiphaga (Grote and Robinson) moths first appeared in traps baited with corn earworm pheromone and conspecific pheromone in April, and were generally present throughout the season until mid to late September. In some years, two peaks of trap capture of H. phloxiphaga males was suggestive of two generations per season, with one flight in April and May and the other in July and August. Although both species were caught primarily in traps baited with their appropriate conspecific pheromone, smaller numbers of both species were captured in traps baited with the heterospecific pheromone. Heliothis phloxiphaga captured in corm earworm pheromone traps can be misidentified as corn earworm, resulting in false positives for corm earworm in commercial sweet corn or overestimates of corn earworm populations.

Key Words: Seasonal phenology, Helicoverpa zea, Heliothis phloxiphaga, corn earworm, trapping, pheromone


Helicoverpa zea (Boddie), the corn earworm (CEW), is a pest of many agricultural crops, particularly corn, tomato, and cotton (Metcalf and Metcalf 1993). The moth is monitored in cropping systems with a four component sex pheromone (Klun ef al. 1980). In the irrigated farming areas of south central Washington, the corn earworm is the key pest of sweet corn, and numerous pesticide applications are required per season to control it. Heliothis phloxiphaga (Grote and Robinson) is generally not a pest but is important as a non-target insect that is sometimes captured in corn earworm pheromone traps (Adams 2001, Hoffman et al. 1991). Heliothis phloxiphaga males respond to the corn earworm pheromone, due to the overlapping chemistries of pheromones of these two species (Kaae et al. 1973, Klun ef al. 1980, Raina et al. 1986). Because of their

' 2700 Seminis Inc., Camino del Sol, Oxnard, CA 93030

overlapping size and coloration, H. phloxiphaga in CEW pheromone traps may be wrongly identified, giving false positive indications for CEW and potentially leading to unnecessary pesticide applications (Adams 2001, Hoffman et a/. 1991). Photographs of the adult stage of both species are figured by Covell (1984), Powell and Opler (2010), and on the Noctuoidea of Canada Website (Troubridge and Lafontaine 2011).

Monitoring of the male corm earworm moth flight with pheromone traps provides information to growers and field scouts that is used to make pest management decisions. Growers of sweet corn in Washington use the traps to indicate the onset of arrival of corm earworm moths, and the need to begin a spray program. In this area, the corn earworm has one to three generations per year (Mayer ef al. 1987), while H. phloxiphaga may be

* Oregon State Department of Agriculture, 635 Capitol St. NE, Salem, OR, USA 97302

3 Corresponding author.

4 Department of Entomology, Washington State University, Pullman, WA 99164

univoltine (Piper and Mulford 1984). Sweet com is first planted in May in eastern Washington, becomes susceptible to attack by the corn earworm in mid July, and is grown by staggered planting dates into October. Growers need to know when to expect corn earworm moth flight, and when to be concerned with distinguishing corn earworm from H. phloxiphaga moths in corn earworm pheromone traps. Seasonal patterns of corm earworm captures in traps have been determined for other geographic and climactic areas (Parajulee et al. 2004, Weber and Ferro 1991) but these reports may not be applicable to irrigated agriculture of Washington.


The primary objective of this study was to determine the seasonal occurrences of adult H. zea and H. phloxiphaga in central Washington. We determined seasonal patterns of moths present as indicated by captures of moths in pheromone-baited traps. In addition, we note responses of the two species to their conspecific and heterospecific sex pheromones. Differences and similarities in the seasonal patterns of the two species should help with interpretation of trap catch data and reduce errors caused by the capture of both species in traps used for corn earworm pest management programs.


Trapping studies were conducted in 1999 to 2004 in south central Washington. The multicolored (white bucket with yellow cone and green lid) Universal Moth Trap (Great Lakes IPM, Vestaburg, MI) was used, with a 6.4 cm2 piece of Vaportape™ (Hercon Environmental, Emigsville, PA) stapled to the inside wall of the trap bucket to kill captured insects. In all cases, traps were checked and captured insects removed each week, and Vaportape™ and lures were replaced every 4 weeks.

Corn earworm lures were the pheromone identified by Klun et al. (1980) consisting of 86.7% (Z)-ll-hexadecenal, 3.3% (Z)-9- hexadecenal, 1.7% (Z)-7-hexadecenal, and 8.3% hexadecanal in a total pheromone load of 1.0 mg per septum, following the methods of Halfhill and McDunough (1985). Pheromone lures for H. phloxiphaga (Raina et al. 1986) were 92% (Z)-11-hexadecenal, 0.4% (Z)-9-hexadecenal, 4.8% hexadecanal, and 2.8% (Z)-11-hexadecen-l-ol in a total pheromone load of 1.0 mg per septum. Pheromone was loaded into red rubber septa (West Co., Lyonville, PA ) that had been pre- extracted twice with methylene chloride in a tumbler. Pheromone was applied to septa as a solution in hexane, at a dosage of 200 microliters per septum. Chemicals were purchased from Farchan Chemicals (Atlanta, GA) and Aldrich Chemical Co. (Milwaukee, WI), and all chemicals were 95% or greater purity. The aldehydic pheromone compounds were purified by elution through a silica gel column with 5% ether in hexane. Pheromone

dispensers were stored in glass vials in a freezer until placed in traps in the field. Pheromone lures were placed in the plastic baskets provided at the center of the inside of the tops of the traps

Traps were set up early in the season near fields to be planted to corn, and were maintained until the moth flights ended in late autumn. Traps were either hung on fences or from stakes put into the ground, at a height of 0.7 to 1.0 m. Traps were checked each week, and Vaportape™ and pheromone lures were replaced each month. Moths in traps were placed in labeled Ziploc® plastic bags for transport to the laboratory, where moths were sorted, identified, and counted. Voucher specimens are deposited in the James Entomological Collection, Department of Entomology, Washington State University, Pullman, WA.

Season-long monitoring of CEW with pheromone traps. Corn earworm moths were trapped throughout the seasons of 1999-2004, with from 4 to 9 trap sites used per season (Table 1). One trap baited with corn earworm pheromone was placed at each site. Trapping sites were selected based on abundant acreage of commercial sweet com to be planted nearby. At the end of the season, traps were recovered from the field, washed with hot soapy water, rinsed with tap water, and exposed outside to sun and open air in wooden bins for a minimum of 30 days before indoor winter storage, to reduce risk of long term contamination of the trap by pheromone.

Season-long monitoring of H.


phloxiphaga with pheromone traps. Heliothis phloxiphaga moths were monitored with traps baited with H. phloxiphaga pheromone, during 1999-2001. Trapping sites, trapping dates, and trap maintenance were the same as those indicated above for corn earworm pheromone traps during the same years (Table 1). One trap baited with 4H. phloxiphaga pheromone was placed at each site, more than 90 meters from the corn

earworm pheromone trap.

We also report H. phloxiphaga moths captured in traps baited with CEW pheromone from 1999-2004, and CEW moths captured in traps baited with H. phloxiphaga pheromone, from 1999-2001. Statistical comparisons were made of numbers of CEW and H. phloxiphaga moths trapped in response to conspecific versus heterospecific sex pheromone lures, using a paired t-test.

Table 1. Dates and lures for season long monitoring of corn earworm.

No. of ; d Pheromones Year Start Date Sites Site Locations ey Yakima Co., Mabton & CEW 1999 paneny ? Toppenish Benton Co., Prosser H. phloxiphaga CEW 2000 20 April ) Grant Co., Mattawa H. phloxiphaga ; Grant Co., Moses L. Franklin Co., CEW 200) popu) : Pasco H. phloxiphaga 002 25 March 4 Yakima Co., Wapato, Granger, CEW Donald, Toppenish 3003 29 March Yakima Co., Toppenish & Moxee CEW Benton Co., Prosser 3004 yl Yakima Co., Toppenish & Moxee CEW

Benton Co., Prosser


Generally, first male corn earworm moths were captured in late May, and males were present continuously through the summer into October (Figure 1). In all years, maximum numbers of male moths were captured in August. However, in 2002 and 2003, a smaller peak of activity was apparent in June. Numbers of moths per trap per week varied widely from year to year, with a maximum of over 250 per trap per week in 2002, but under 70 moths per trap per week in 1999, 2000, and 2003.

For 1999-2001, data for H. phloxiphaga are from traps baited with conspecific pheromone, and for 2002-2004, data for H. phloxiphaga are from traps baited with CEW pheromone. Generally, male H. phloxiphaga moths were first captured in pheromone traps in April (Figure 2). In 1999 and 2000, traps were not placed in the field early enough to

determine the onset of H. phloxiphaga flight and males were captured during the first week of the study. In all 6 years, there were two separate periods of flight activity of male H. Phloxiphaga. The first period was in late April to early June, and the second period was mid July to late August. Numbers of moths trapped varied greatly from year to year, with a maximum of over 24 male moths per trap per week in 2004, and a maximum of fewer than 5 moths per week in 1999.

Traps baited with CEW pheromone captured primarily CEW moths, and traps baited with H. phloxiphaga pheromone captured primarily H. phloxiphaga (Table 2). In 1999, 2000, and 2001, when the pheromones of both CEW and H. phloxiphaga were maintained throughout the season, CEW moths were captured primarily in traps baited with the CEW pheromone, with relatively few

captured in traps baited with the H. phloxiphaga pheromone. Numbers of male H. phloxiphaga captured were numerically but not significantly greater in traps baited with


the H. phloxiphaga pheromone compared to traps baited with the CEW pheromone (Table 2).


The primary objective of this study was to characterize the seasonal patterns of captures of CEW and H. phloxiphaga moths in traps in southcentral Washington as an indicator of adult moth presence in corn fields. Particular aspects of moth seasonal patterns that are potentially of interest include the onset of moth flight in the spring and cessation in autumn, peak activity periods, and numbers of generation per year. In this case, we are also

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interested in determining periods of risk of misidentifying H. phloxiphaga as CEW, in relation to CEW pest management. Although numbers of CEW moths captured in pheromone traps varied greatly from year to year, the cessation, termination, and peak periods of moth activity were similar throughout this 6 year period. The period during which corn earworm moths were active broadly encompasses the entire period during

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Figure 1. Mean (+ SE) numbers of male corn earworm moths captured per week per trap, in traps baited with corn earworm pheromone, for 1999, 2000, 2001, 2002, 2003, and 2004.




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Figure 2. Mean (t SEM) numbers of male H. phloxiphaga moths captured per week per trap, in traps baited with H. phloxiphaga pheromone (1999, 2000 and 2001) or corn earworm pheromone (2002,

2003, 2004).

which corn is grown in this same area. Corn is normally first planted after last frost, in mid to late May, and staggered plantings and harvesting continue into early October. However, corn is a suitable oviposition site for CEW beginning with the silking stage, which starts in late June. Earlier in the season, CEW moths might be infesting alternate host plants, possibly weed and wild flower species (Hardwick 1965, 1996; Neunzig 1963; Robinson et al. 2002). It is assumed that the end of moth flight in autumn may occur primarily as a result of decreasing temperatures making moth flight impossible. In contrast to evidence for CEW migrating

from south to north (Hartstack et al. 1982; Westbrook et al. 1997), there is no documentation of north to south migration. If such a migration occurs, it could explain in part the disappearance of the moth in early autumn in south central Washington.

Mayer et al. (1987) reported 1-3 generations of CEW per year in Washington. Our data show nearly continuous moth activity for 5 months, from late May into mid to late October, without evidence of distinct generations. Corn earworm may overwinter in the southern Columbia Basin of Washington, as pupae in soil (Eichman 1940, Klostermeyer 1968), first emerging in May. The

interpretation of trap catch data may be complicated by immigration of CEW populations from the southwestern U. S. In other areas of North America, CEW moths migrate (Hartstack et al. 1982; Hendrix et al. 1987; Lingren et al. 1993, 1994; Westbrook et al. 1997). Strong increases in numbers of male CEW moths in pheromone traps in August may have been due to reproduction by earlier emerging moths, and/or migrating moths that arrive in south central Washington with infrequent weather fronts.

The seasonal activity and abundance of the com earworm moth varies geographically, probably in response to climactic factors and their impact on migration, reproduction, and other behaviors, as well as regional makeup and abundance of crops and crop planting and harvest cycles. The amplitudes of the seasonal patterns of catches of CEW moths in pheromone traps in south central Washington were small compared to that observed in Texas by Parajulee et al. (2004). Captures of moths in pheromone traps often began in April in Texas, compared to May in Washington, and ended in October as it did in our study in Washington. In Mississippi, CEW males were


captured in pheromone traps sporadically from early June to the end of September (Hayes 1991). In Massachusetts, CEW moth flight appears to begin much later than in south central Washington despite a similar latitude. Weber and Ferro (1991) captured CEW moths in pheromone traps in Massachusetts from early July into early September, which is a seasonal activity period that is nearly 2 months shorter than seen in our study.

Piper and Mulford (1984) reported that H. Dhloxiphaga was univoltine in Washington. The data presented here indicate consistently over the 6 years that there were two periods of increased catches of moths in traps, indicating possibly two generations per year. The apparent two maxima of activity indicated by pheromone traps suggests that a first adult generation occurred in April/May and a second generation in July/August. However, Hoffman et al. (1991) did not see more than one peak of captures of H. phloxiphaga in corn earworm pheromone traps in California, although adult activity was noted over a period of 6 months, from February to September. Certainly, multiple generations of a moth species can occur within a season

Table 2

Mean (+SE) numbers of male corn earworm and H. phloxiphaga moths captured per season per trap baited with corn earworm and H. phloxiphaga sex pheromones.

Moth species Corn earworm captured pheromone


Corn earworm 218.3 + 64.2a

H. phloxiphaga 6.9+2.4a 2000

Corn earworm 427.6 + 52.3a

H. phloxiphaga 25.2 + 6.4a

2001 Corn earworm

H. phloxiphaga

415.8 + 144.0a

22 ea

H. phloxiphaga - pheromone 14+1.1b 9 12.4+3.9a 9 3.8 +'1.0b 5 44.2+ 10.9a 5 2.) + 0.9b 4 16.0+5.8a 4

Means within a row followed by the same letter are not significantly different by a paired t-test at P < 0.05.


without the appearance of distinct separated periods of flight indicated in pheromone traps.

In all six years of our study, the first flight of H. phloxiphaga began about one month before the first catches of CEW moths in traps, and captures of H. phloxiphaga moths ended about one month before the last captures of CEW moths. Peak numbers of possible second flight H. phloxiphaga populations overlapped somewhat with peak numbers of CEW in early August, although the numbers of H. phloxiphaga in H. Dhloxiphaga pheromone traps were considerably less than CEW moths trapped with corn earworm pheromone. It appears then that CEW monitoring traps in May might easily provide misleading information from the capture of H. phloxiphaga misidentified as CEW, but before the expected appearance of CEW. Also, in August, H. phloxiphaga captured in CEW pheromone traps may inflate counts of CEW trap catch, if misidentified. However, those numbers would usually be minor in relation to the numbers of CEW moths trapped at that time. It is most important to positively identify the two species early in the season, and again in late

summer when both are present, but in situations where corn earworm populations are expected to be low.

Although the chemistry of the H. phloxiphaga sex pheromone overlaps with that of the CEW pheromone, H. phloxiphaga responses to the CEW lure are not consistently a problem with CEW monitoring programs in North America. Weber and Ferro (1991) found 5 non-target species of noctuids captured in CEW monitoring traps in Massachusetts, but did not indicate the trapping of ok phloxiphaga. Chapin et al. (1997) reported non-target moths captured in corn earworm traps, but captured only one H. phloxiphaga moth compared to over 25,000 CEW. However, in eastern Washington, H. phloxiphaga is consistently present throughout much of the corn growing season and is routinely captured in corn earworm pheromone traps (Adams 2001), and Hoffman et al. (1991) trapped it in sweet corn fields throughout California. Growers can reduce costs and pesticide used by distinguishing the two species when captured in com earworm traps, and by recognizing that corm earworm are unlikely to be present before late May.


Assistance with lures, traps, and moths was provided by J. Brumley, P. Chapman, J. Dedlow, D. Larson, D. Lovelace, and C. Martin. We thank L. Anderson, A. Bassani, R. Earl, L. Elder, R. Halvorson, C. Martin, R. Martinez, J. Rice, H. Sealock, P. Smith and B. Thorington for access to their fields. Del Monte Corporation, Toppenish, WA provided

a vehicle for use in this study. This work was supported in part by funding from the Columbia Basin Vegetable Processors Association, the America Farmland Trust Foundation, the Environmental Protection Agency, and a USDA, Western Region IPM grant.


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Occurrence of the Western Flower Thrips, Frankliniella occidentalis, and potential predators on host plants in near- orchard habitats of Washington and Oregon (Thysanoptera: Thripidae)



One hundred thirty species of native and introduced plants growing in uncultivated land adjacent to apple and pear orchards of central Washington and northern Oregon were sampled for the presence of the western flower thrips (WFT) Frankliniella occidentalis (Pergande, 1895) and potential thrips predators. Plants were sampled primarily while in flower. Flowering hosts for WFT were available from late-March to late-October. Adult WFT occurred on 119 plant species and presumed WFT larvae were present on 108 of 119 species. Maximum observed WFT density on several plant species exceeded 100 individuals (adults and larvae) per gram dry weight of plant material. The most abundant predator was Orius tristicolor (White, 1879) (Heteroptera: Anthocoridae). It was collected on 64 plant species, all of which were hosts for WFT. The second most abundant predators were spiders (Araneae). Small spider immatures (first and second instars) of several species were common on certain host plants, and are likely to feed on WFT.

Key Words: Frankliniella occidentalis, western flower thrips, host plants, predators, Orius tristicolor, Araneae, spiders.


The western flower thrips (WFT) Frankliniella occidentalis (Pergande, 1895), was originally distributed throughout western North America (Kirk and Terry 2003). In the past 30 years WFT has spread to much of the rest of North America and now also occurs throughout Europe and parts of North Africa (Kirk and Terry 2003). It is a pest in both the field and the greenhouse, attacks a large number of crops, and causes damage by feeding, oviposition, and most importantly, transmission of Tospoviruses (Reitz 2009). WET is an important secondary pest of certain apple varieties in the Pacific Northwest, producing a pale, cosmetic blemish known as a pansy spot that forms around the site of oviposition (Venables 1925; Madsen and Jack 1966). Although the damage is superficial, affected fruit may be downgraded at harvest (Madsen and Jack 1966; Terry 1991). Control of WFT on apple can be challenging because it occurs on trees primarily when pollinators,

especially honeybees, Apis mellifera Linnaeus, 1758, are active in the orchard canopy. It has also been difficult to determine when, during fruit formation, damage-causing Oviposition occurs and, consequently, when control measures are most needed (Cockfield et al. 2007).

Host plant utilization by WFT is very broad. Bryan and Smith (1956) found it on 139 plant species (representing 45 families) in California, which is within the pest’s original geographic range. In areas to which it has spread, host plant utilization is also broad, and in Hawaii it was found on 48 plant species on the island of Maui (Yudin ef al. 1986). Chellemi et al. (1994) found it on 24 of 37 plant species surveyed in Florida within a decade after its first detection. In a study done barely ten years after the insect was first reported all 49 plant species sampled in Turkey harbored WFT (Atakan and Uygur 2005). In Chile, where it has become a serious

' Yakima Agricultural Research Laboratory, United States Department of Agriculture Agricultural Research

Service, 5230 Konnowac Pass Road, Wapato, WA 98951

Corresponding author: gene,miliczky@ars.usda,gov

agricultural pest, WFT occurred on 50 of 55 plant species and appears to have supplanted a native species of Frankliniella as the most common thrips species (Ripa et al. 2009).

A number of predators are known to attack WFT (Sabelis and Van Rijn 1997). Few of the studies that have reported on WFT’s occurrence on non-crop plant species have also reported on the presence of predator species. Northfield et al. (2008) studied the population dynamics of WFT on seven uncultivated host plants and also reported on the occurrence of the important thrips predator Orius insidiosus (Say, 1832) (Heteroptera: Anthocoridae). Tommasini (2004) monitored Orius populations on known host plants of WEFT in Italy and found that several species of Orius commonly occurred at high densities on


a number of these host plants, apparently in association with WFT.

In this study, we surveyed native and introduced plant species in fruit-growing regions of central Washington and northern Oregon where WFT is a secondary pest of certain apple varieties. Our objectives were to 1) gain an understanding of WFT utilization of non-cultivated host plants typical of near- orchard habitats in the study areas, 2) develop a better understanding of WFT phenology across the season, and 3) improve our understanding of known and potential WFT predators occurring on these non-cultivated host plants, with emphasis on minute pirate bugs (Heteroptera: Anthocoridae) and spiders (Araneae).


Study Sites. This study was conducted at 11 sites in Washington State and two sites in northern Oregon (Table 1). Virtually all sampling was done in native habitat immediately adjacent to orchards, generally within 100 m of an orchard edge; a few plant species of interest that occurred in the understory of orchards were also sampled. Most of the sites were in Yakima County, Washington, located in the south-central part of the state. Two sites were near Hood River in northern Oregon (Table 1).

With one exception, each tract of native habitat was at least several hectares in area and adjacent to orchard habitat. The only exception was a tract comprising a 25 m wide strip of native vegetation occurring between an orchard and an irrigation canal. Native habitat at all Yakima County and the Grant County locales was sagebrush steppe (Table 1). Sagebrush steppe at Hambleton, Durey, and Sunset fell within the lithosol zone of Taylor (1992), and is characterized by thin, rocky soils and a diverse flora. In mid-May at these locations we noted 25 or more plant species in flower simultaneously. Sagebrush steppe at the remaining Yakima County sites and the Grant County site fell within the standard-type zone (Taylor 1992), characterized by moderately deep soil and vegetation dominated by grasses and _ tall sagebrush, Artemisia tridentata Nutt. (Asteraceae). The Ing, Wells, and Alway sites

consisted of mixed hardwood/coniferous woodland. Trees included Pinus ponderosa Dougl. (Pinaceae), Pseudotsuga menziesii (Mirbel) Franco (Pinaceae), Acer macrophyllum Pursh (Aceraceae), and Quercus garryana Dougl. (Fagaceae). Understories at all three sites consisted of a variety of shrubs and forbs.

Sampling for thrips and predators. The Yakima County study sites were visited at approximately weekly intervals during 2002 from early April to late October. Due to greater travel distances the Grant County site was visited bi-weekly, and the Chelan County and Oregon sites were visited monthly from April to July. Sampling in 2003 was limited to selected plant species (see below) at sites in Yakima County. Durey and Hambleton were visited weekly from late March to late October, while the other Yakima County sites were visited when species of interest were in flower. During each visit, observations were made of plants in flower and whether a species was at early, full, or late bloom. Notes were also made of species that had recently passed out of bloom and of those that were about to come into bloom.

Samples were collected by removing inflorescences or individual flowers with scissors or pruning shears and immediately placing them in 3.8L, self-sealing, plastic bags. Care was taken when removing flowers to avoid dislodging insects and spiders. Since


Table 1. Sampling sites, habitat type at each site, and sampling frequencies.


Site Location (county)

Hambleton 3.5 km N Tieton (Yakima)

D 4.5 km NNW Tieton urey

(Yakima) Sunset 4.5 km S Tieton (Yakima) Caren 3 km SSE Union Gap (Yakima) Leach 6 km NNE Zillah (Yakima) Lynch 5.5 km NE Zillah (Yakima) Hattrup 5 km SSE Moxee (Yakima) Valicoff oe cane USDA 18 km ESE Moxee (Yakima) Knutson 10 km SE Mattawa (Grant) Alway Peshastin (Chelan) Ing (Oregon) 2 km SSE Hood River (Hood River) Wells (Oregon) : wae feet

13 Sampling Habitat 2002 2003

Sagebrush-steppe W W

Sagebrush-steppe W W Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe W I Sagebrush-steppe BW --

Mixed hardwoods and conifers M --

Mixed hardwoods and conifers M --

Mixed hardwoods and conifers M --

|W, weekly; BW, bi-weekly; M, Monthly; I, irregularly.

WFT is primarily associated with flowers, non-flower plant parts such as leaves and stems were kept to a minimum in samples during the bloom periods. Samples taken outside of the bloom period included primarily rapidly growing vegetative tissue. Samples were transported in a cooled ice chest to the laboratory where they were held in a refrigerated room until processed, generally within 24 h. The amount of plant material collected for a sample varied from species to species depending upon its abundance at a site and the nature of its inflorescence. Abundant species with large or bulky inflorescences were collected in sufficient quantity to loosely fill a bag. Smaller quantities were obtained of

less abundant species and those with small, more difficult to collect flowers. Blooms were collected from several individual plants per species at a site to obtain a sample. The number of individual plants sampled per species depended upon the density of that species at the site.

We were interested in each plant species primarily during its bloom period. A single, flowering period sample was obtained for some species, but many were sampled more than once during bloom. Several species were sampled weekly while in flower with additional samples taken during the pre-bloom and post-bloom periods. The extreme example was bitterbrush Purshia tridentata (Pursh) DC

(Rosaceae), which was sampled weekly at the Durey site from 16 April to 28 October 2003, for a total of 29 sample dates. Most species were sampled at one or two locations, but samples from arrowleaf balsamroot Balsamorhiza sagitatta (Pursh) Nutt. (Asteraceae), a common, widespread species, were obtained at nine sites. In 2002, most of the plant species at each site were sampled on at least one date. Based on the 2002 findings, 16 species that supported high numbers of thrips and predators were monitored in 2003.

Extraction of arthropods. Thrips and predatory arthropods were extracted from plant material using Berlese funnels. Heat from 40 watt light bulbs was used to force arthropods out of the plant material and into 500 ml plastic jars each containing 50 ml of 70% isopropyl alcohol. Samples were held in the funnels for 24-48 h depending on the quantity of plant material. This length of time was sufficient to dry the plant material, which was then weighed on an electronic balance. We calculated thrips numbers per gram dry weight of plant material.

Processing of samples. WFT was the only thrips identified to species (by comparison with vouchers). Species other than WFT were generally few in number (see Results). Larval thrips were counted but were not identified. When the adult thrips in a sample were exclusively WFT we assumed that all larval thrips were