Updated 01/16/09

Eric H. LaGasa¹ Patrik Hertzog², Dan Barshis², Kelley Turner² and Hannah Smith²

Background

Figure 1.

In 1998 and 1999, three male adults of European poplar shoot borer (EPSB), Gypsonoma aceriana (Duponchel), were collected, as non-target captures in various exotic pest surveys, in western Washington State. The first EPSB was found in the Seattle port area, in a mercury vapor light trap. Another specimen emerged inside a cage placed over leaf litter beneath hybrid poplars at the Washington State University Research Station near Puyallup, in Pierce Co. (T. Murray, collector). A third was found at a tree nursery near Roy, also in Pierce Co., in a trap baited with European pine shoot moth, Rhyacionia buoliana [D. & S.], lure. (Figure 1.)

EPSB is a notable pest of many poplar species, Populus spp. (Salacaceae), as well as hybrids in plantations and nurseries in Europe, where infestation of up to 93.7% of growing tips has been recently reported (Georgiev and Velcheva 1999). Young larvae mine leaves and older larvae bore into terminal shoots, often causing gall-like swellings (Bradley et al. 1979).

In exterior appearance, adults of G. aceriana (Kuznetsov 1987) (Figure 2.) are very similar to those of the North American cottonwood twig borer, G. haimbachiana (Kearfott) (Miller 1987) Genital anatomy provides the most reliable means of distinguishing the two species. For a more thorough review of EPSB pest status, biology, diagnostic characters, and the associated technical literature, please see Miller and LaGasa, 2001.

2001 Project Objectives

Figure 2. Adult Gypsonoma aceriana (Duponchel)

1. Determine survey methods and survey area priorities.

• Research / acquire suitable pheromone attractant, dispensers, and trap type to conduct adult delimiting survey.
• Plan a prioritized trap coverage of contiguous areas of poplar hosts in western Washington.

2. Conduct a preliminary delimiting survey of EPSB distribution in western Washington.

• Conduct survey to delimit EPSB in as large an area as resources allow, beginning at known positive sites.

3. Observe and record biology and impacts of EPSB in Western Washington.

• Examine host trees at sites of higher EPSB pheromone-trap captures for evidence of infestation.
  
• Capture digital graphics of EPSB life stages, biology, and feeding damage where possible.

Project Methods and Materials

Five hundred and forty two pheromone-lure baited traps were placed in counties along the Interstate-5 corridor in western Washington, from the Canadian border south to Clark County on the Columbia River / Oregon border. Trap placement, by county, is presented in Table 1. Traps were hung in roadside or residential yard Populus spp. trees, primarily cottonwood and various ornamental poplar varieties.

Because the principal survey objective was delimitation of EPSB in Western Washington, project funding allowed only three months of field activities, which limited most EPSB flight-season data collected. Trap placement began in May, to allow for completion of all initial trap sets by the beginning of expected adult moth flight in late-June or early-July, and most traps were removed by the end of July. To collect additional adult-flight information, trapping in Pierce County, where EPSB captures were highest in initial trap-captures, was continued until early- September.

Pherocon 2® type traps (a.k.a. "diamond" traps) were used in this survey, based on trap performance in prior WSDA CAPS surveys, ease of use, and the avoidance of small-bird capture/mortality (which is a problem with other trap designs, particularly “wing-traps”). Traps were baited with pheromone-lures provided by the USDA APHIS Otis Methods Development Center. The EPSB pheromone-lures consisted of gray rubber septa (West Co., Lionville, PA.; cat.no. 1060-0275), each loaded with 0.1 ml (1 mg) of the following pheromone components (ISCA Technologies, Inc., Riverside, CA) in an approximate 3:1 mix:

(E)-10-Dodecenyl acetate (0.725 mg/lure)
(E)-10-Dodecen-1-ol (0.275 mg/lure)

Pheromone lures were changed every two weeks as much as possible during the observed period of adult flight. Traps with specimens were processed at the Olympia Entomology Lab, where EPSB specimens present were identified and counted. Selected sub-samples of EPSB were removed from the traps with Hemo-D citrus based solvent and had genitalia extracted and cleared (in KOH) to confirm identification.

To document EPSB biology, several visits to positive trap sites were conducted to collect and photograph life stages and host plant damage. EPSB larvae and other unknown immature insects found infesting poplar tips in May were also reared to the adult stage and/or identified at the WSDA Olympia Entomology Lab. Larvae were reared in individual containers, in the original poplar host material as much as possible.

Digital image files created for this project were captured with a Nikon® 990 camera, hand-held or mounted on a Leica® MS5 microscope, and macro-photographic images were created using daylight-corrected fiber-optic incandescent lighting and mylar diffuser-filters. Images were also cropped, adjusted, and labeled with Photoshop® 5.5.

Project Results and Discussion

A total of 4,245 adult male EPSB were captured in the delimiting survey traps, with EPSB recorded from every county surveyed. Catch data is summarized by county in Table 2.

These survey results clearly show that EPSB is well established across most of Western Washington. However, it should be noted that direct comparison of summary trap information from one county to another is difficult, given the variation in trapping duration (e.g. survey timeframes) due to survey emphasis, travel distances for field staff, and other variables.

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This project was a cooperative effort of the Washington State Department of Agriculture, Agriculture and Agri-Food Canada, and the USDA Animal and Plant Health Inspection Service (APHIS). Funding for field and lab support staff was provided in part by a Cooperative Agricultural Pest Survey (CAPS) grant from the USDA APHIS Western Region (#01-8553- 0249-CA). 1Eric LaGasa, Chief Entomologist, Pest Program / Plant Protection Division, Washington State Department of Agriculture,  P.O. Box 42560, Olympia, Washington  98504-2560,  (360) 902-2063  PestProgram@agr.wa.gov 2Entomology Aides (Project) - Washington State Dept. of Agriculture, Olympia, Washington 98504-2560 Inquiries regarding availability of this publication in alternative formats should be directed to the WSDA Receptionist at (360) 902-1976.