Updated 01/16/09

Eric H. LaGasa¹ Jasmine Loucks², and Lisa Spurrier²

Figure 1. Wireworm Larva. Figure 2. Adult Click Beetles

Background

Wireworms are the juvenile stage (larvae) of click beetles (family Elateridae), a diverse group of beetles that includes beneficial as well as plant-feeding species. Pest species live in soil where the tough, wire-like larvae feed on seeds, plant roots, and underground plant parts. Crop damage begins in the spring, when larvae can be particularly destructive of planted seeds. During the summer and early fall, wireworms feed on the developing root systems and stems of many plants, including grains, corn and garden vegetables. Larvae also burrow into the tubers and stems of potatoes and ornamentals such as dahlias, gladioluses and tuberous begonias.

Two European pest wireworms, Agriotes obscurus (L.) and Agriotes lineatus (L.) (Figures 1 and 2), were known to be present in British Columbia, Canada, since 1950 and A. obscurus was found for the first time in the United States near Lynden, in Washington State in 1997 (Vernon and Päts, 1997). In 2000, a preliminary WSDA/USDACAPS detection survey of areas of western Washington found both species in several counties along the east side of Puget Sound (Figures 3 and 4, from LaGasa et. al., 2000).

In recent years these two species have become the most important pests of many crops throughout the lower Frasier Valley, causing between $500,000.00 and $800,000.00 in crop losses in 1994 (Vernon, 1998). Both species are major economic pests in Europe and western Asia (USDA APHIS, 1978).

Figure 3. A. obscurus Traps 2000 Figure 4. A. lineatus Traps 2000

For more information on these pest wireworms, damage, monitoring, and management in the PNW region, a number of internet links and recent publications is included at the end of this report.

2004 Project Objectives

1. Delimit Agriotes lineatus and A. obscurus distribution in selected areas of western Washington.

• Survey to detect or delimit Agriotes spp. in areas adjacent to known populations (in Pierce county) and in the adjacent county (Thurston county).
• Survey to detect or delimit Agriotes spp. in Clark county, in collaboration with the Oregon Department of Agriculture to survey the greater Vancouver, Washington / Portland, Oregon port area.

Project Methods and Materials

This one-person field survey used pheromone-traps and lures recently developed by Dr. Bob Vernon (Agriculture Canada) and PheroTech Inc. of British Columbia, Canada.

Figure 5. Click Beetle Trap Figure 6. Trap Site Preparation Figure 7. Trap Installation Figure 8. Checking Trap Contents

The trap captures and confines adult beetles that are attracted to a internal pheromone lure and fall in after ascending shallow ramps. Pheromone lure formulation remains proprietary information at this point, but the trap configuration is presented here courtesy of PheroTech Inc. (Figure 5). No kill agent or preservative was used in the traps, which relied on regular servicing to provide specimens in good condition.

Physical criteria for trap sites included proximity to areas of turf, pasture, or other grassy locations, which are considered favored wireworm habitat, and protected situations where traps would be less likely disturbed or damaged (Figure 6.). Traps were placed at ground level, with entry ramps flush with or slightly covered by adjacent soil to provide unimpeded beetle entry (Figure 7). Checking and sample collection involved removal of one of the ramp inserts and shaking the trap contents into a tray (Figure 8).

Traps were placed beginning in early March and checked weekly until removal in early June, to coincide with spring adult beetle activity. Survey sites were around port facilities or navigable waterways, and near previous positive sites in Pierce county.

In total, 159 sites were trapped in this survey. Trap site numbers and catch status by county are presented in Table 1. Beetles captured were identified in the WSDA Olympia Entomology Lab and new county record collections were sent to Dr. Paul Johnson, a USDA Systematic Entomology Laboratory identification collaborator at the University of South Dakota, for confirmation (received July 29, 2004).

Project Results and Discussion

Both A. lineatus and A. obscurus were found at sites in Pierce and Thurston counties, but neither were collected in Clark County (Table 1.). The Pierce County collections of A. obscurus represent the first detections in that county, and the Thurston County collections are the first for both species. Survey results by trap site for both target species are presented in figures 9 through 12.

Figure 9. Pierce County A. lineatus Survey Sites Figure 10. Pierce County A. obscurus Survey Sites Figure 11. Thurston County Survey Sites Figure 12. Clark County Survey Sites

This surveys' collections of both A. lineatus and A. obscurus at multiple sites in Pierce and Thurston counties continue to suggest both pests may be widely established throughout the Puget Sound area. However, significantly more survey is needed to make that determination. Whether the detected populations in Snohomish (in 2000), Pierce, and Thurston counties represent natural spread from British Columbia (i.e. are part of a contiguous population) or are the result of independent introductions has not been determined.

Figure 13. Agriotes lineatus and A obscurus Captured by Week in Pierce County in 2004.

Capture data does indicate survey timing was appropriate to record adult beetle phenology (emergence timing) in Pierce County this year, and the total weekly beetle capture at all Pierce County trap sites is displayed in figure 13. Adult beetle activity for both species apparently peaked about the second week in April and gradually declined until late May.

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This survey was funded in part by a Cooperative Agricultural Pest Survey (CAPS) grant from the USDA APHIS Western Region (#02-8553-0249-CA) and does not necessarily reflect APHIS' views. 1 Eric 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 2 WSDA Entomology Aide (Project Field Staff) This report is provided as a public resource for the detection and identification of insect pests described. This entire report, as well as individual graphic images, may be freely copied, distributed, and used in electronic and printed format as long as they are not modified for content or used for commercial purposes.