Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), can cause substantial
damage to a wide range of agronomic and vegetable crops. Two introduced species of wireworm
(Agriotes spp.), have spread in Washington resulting in serious economic damage to high value
vegetable crops. Wireworms thrive on pasture and grain rotations, which are commonly used by
growers to maintain and build soil organic matter. Growers in western Washington have
indicated that wireworms are a primary pest challenge and options for control of this pest are
very limited. Using a preferred host as a trap crop planted near the cash crop is a potential low
cost, environmentally friendly option for wireworm management. Using lettuce as a model crop,
project personnel and cooperating farmers will evaluate trap cropping with wheat as compared to
a spinosad bait product and a no management control. This project will also document current
Agriotes distribution in Washington State using pheromone traps.
The project team includes agricultural professionals with extensive experience in conducting onfarm
research as well as a group of experienced vegetable growers who are proactively engaged
in efforts to improve wireworm management. Project results will be shared directly with
producers and agricultural professionals. Project personnel will hold on-farm field days to
facilitate exchange of information between host farmers and with other producers in the region.
Outreach efforts will also include presentations at established events locally, regionally and
nationally. Fact sheets and trial summaries will be developed to provide accessible information
to producers. The proposed study will engage WSU volunteers in surveying Agriotes spp.
distribution. Utilizing this network has potential to expand the societal benefit of the proposed
research beyond commercial production to the greater community-based food system.
Objective 1. Evaluate wheat as a trap crop for control of Agriotes spp. in transplanted head lettuce production.
Objective 2. Conduct a survey of Agriotes spp. distribution across Washington State.
Objective 1. Evaluate wheat as a trap crop for control of Agriotes spp. in transplanted head lettuce production. This trial will be repeated for at least two years, providing a robust data set to evaluate trap cropping with wheat across multiple locations and growing seasons.
In 2018 management trial was set up at cooperating farms in San Juan County (3 sites), Skagit County (2 sites) and Thurston County (1 site).
Trial Set Up:
- Quantified wireworm population density at each collaborating farm. Bait traps (1 cup of wheat soaked for 12hrs in a stocking) were buried ~6in deep for one week to gauge wireworm pressure prior to planting. After one week bait traps (4 per site) were dug up and the number of wireworm larval feeding on wheat in the stockings was counted. Method modified from Esser 2012. Wireworm Scouting.
- One composite soil sample was taken from each site and submitted for soil nutrient test at Soil Test Labs, Mose Lake, WA to determine baseline soil nutrient condition.
- Lettuce (cv ‘Mirlo’) was be grown from seed in 72 cell trays for three weeks prior to transplanting.
- Establish on-farm trials. The following seven treatments were established in a randomized complete block design with four replicates at each farm. Treatments: 1.) Control: lettuce transplanted without wireworm management; 2.) Spinosad: bait product (Seduce) applied one week prior to lettuce transplanting; 3.) 2x Spinosad: Spinosad applied one week prior to transplanting and at transplanting; 4.) Wheat: Wheat trap crop planted one week prior to lettuce transplanting; 5.) 2X Wheat: Wheat planted one week prior to transplanting and at transplanting. 6.) Wheat + spinosad: Wheat planted and spinosad applied one week prior to transplanting; 7.) 2x Wheat + Spinosad: Wheat planted and spinosad applied one week prior to transplanting and at transplanting.
- Each plot was 6ft long by 4ft wide with a 3ft buffer between plots. Wheat was planted between lettuce rows at rate of 0.5 ounce per 3ft. Spinosad bait will be applied between lettuce rows at rate of 20 lbs product/acre according to product label. Trial start date varied depending on local growing conditions and farmer cooperator needs.
- Soil temperature was monitored for the duration of the field trials using a HOBO data logger recording at hourly intervals at a depth of 6in.
- Lettuce mortality in each plot was recorded weekly following transplanting.
- Wireworm density between lettuce rows in each plot (measured by taking soil core and counting larvae present) was conducted one week prior to transplanting, at transplanting and every week following transplanting. This helped determine if wireworms were being attracted to spinosad bait and or wheat trap crop.
- Lettuce was harvested and weigh after four weeks of growing in the field to determine a fresh weight yield and average size of lettuce plants.
Objective 2. Conduct a survey of Agriotes spp. distribution across Washington state.
This work is planned to begin in early 2019.
- Using on-line webinars, recruit and train Washington State University Master Gardeners and other clientele from key locations statewide to set up pheromone traps and maintain samples collected from traps through the duration of adult Agriotes seasonal activity
- Distribute pheromone traps developed for Agriotes obscures and Agriotes lineatus to Master Gardeners and other WSU Extension volunteers across the state
- Deploy traps in established grassland near or in agricultural production areas. February
- Monitor pheromone traps bi-monthly to determine number and species of adult males attracted to the pheromone lures.
- Process samples and confirmation of species identification by WSDA entomologists.
Objective 1 Results and Discussion
Results from baseline monitoring of wireworms is presented in the table below:
|Year||County||Farm||Average Wireworms/ Bait Trap|
|2018||San Juan||Maple Rock||7|
|2018||San Juan||Lopez Harvest||2|
|2018||San Juan||Mama Bird||33|
Despite reports of wireworm damage at farm sites in Skagit and Thurston County, no wireworms were caught using bait traps located at Skagit Flats or Viva Farms and only 2 wireworms were found at Calliope Farm in Thurston County. Additionally it was found that the wireworms present in the trial at Calliope Farm where Limonius canus (Pacific Coast wireworms), where as the wireworms in San Juan County were Agrioties spp.. In 2019 the project team will look for new locations with higher wireworm pressure in Skagit and Thurston County and continue to monitor for species differences. San Juan County sites all had high levels of wireworm pressure with very high levels found at Mama Bird Farm.
Lettuce mortality, yield and wireworm density and soil temperature data were collected and are being analyzed and prepared to presented at future outreach events and in publications.
Objective 2 Results and Discussion
No results to report to date. This component of the project is scheduled to start in early 2019.
Educational & Outreach Activities
Outreach to Date
Consultations – Project personnel have consulted one-on-one with a minimum of 10 growers and agricultural professionals on wireworm management and distribution.
Field Day – July, 2018. Poster presentation at the Washington State University Northwest Washington Research and Extension Center. Reached an estimated 10 agricultural professionals and 10 Farmers.
San Juan County Fair – August 15- 18, 2018. Wireworm poster was displayed as part of the WSU Agricultural Tent.
On-Farm Demonstrations – Wireworm management trials were conducted on six working farms. Growers were involved in setting up trial and evaluating results and the project was shared with farm owners and field crews. Reached at least 10 farmer cooperators and farm staff.
Outreach to WSU Master Gardener volunteers on click beetle pheromone trapping is scheduled to start in the end of January 2019.
We will be delivering a poster presentation at the Organic Farming Research Foundation, Organic Agriculture Research Forum, Portland, Oregon, Feb 16th, 2019.
A talk to the Whidbey Island Grower’s Association is scheduled for March 4th, 2019.
On-farm field days are being planned for summer of 2019 to showcase trials and preliminary results in San Juan, Skagit and Thurston counties.
Year one results are being prepared for presentation. Gain in knowledge hasn't been evaluated yet.
This is year one of a three year project. Impacts and outcomes will be evaluated over the next two years as preliminary results are presented.