Final report for OW18-018
Project Information
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.
Cooperators
- (Educator and Researcher)
- (Educator and Researcher)
- (Educator and Researcher)
- (Educator and Researcher)
Research
Objective 1. Evaluate wheat as a trap crop for control of Agriotes spp. in transplanted head lettuce production. This trial was repeated across 3 years including a total of 14 locations years in western Washington.
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). In 2019 management trial was set up at cooperating farms in San Juan County (3 sites), Island County (1 site), Skagit County (1 site), and Thurston County (1 site). In 2020 management trial was set up at cooperating farms in San Juan County (3 sites) and at WSU Mount Vernon Research and Extension Center in Skagit County (1 site). Additionally an observational trial with potatoes was planted in Thurston County in 2020. Over the three years (2018-2020) 10 grower cooperators hosted trials and were involved with the research.
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 'Muir') was be grown from seed in 72 cell trays for three to four 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.
Measurements:
- 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 weighed 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.
- Washington State University Master Gardeners, Extension Staff and Faculty were recruited 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 as well as WSU Extension volunteers across the state in 2019 and 2020. In 2021 lures for the native Limonius genus were included.
- Traps were deployed in established grassland areas from approximately April to July.
- Pheromone traps were monitored weekly to determine number and species of adult males attracted to the pheromone lures.
- Samples were collected and frozen for project team members to count and confirm species identification.
Objective 1 Results and Discussion
The wireworm trap crop trial was conducted at multiple sites over three years. Baseline wireworm pressure varied widely from an average of zero wireworms found in a bait trap after one week to over 33 (Table 1).
Table 1. Presence of wireworms (Agriotes spp.) in wheat bait traps after 1 week.
|
Year |
Farm |
County |
Average Wireworms/ Bait Trap |
|
2018 |
Calliope |
Thurston |
N/A |
|
2018 |
Lopez Harvest |
San Juan |
2 |
|
2018 |
Mama Bird |
San Juan |
33.25 |
|
2018 |
Maple Rock |
San Juan |
7.25 |
|
2019 |
Deep Harvest |
Island |
N/A |
|
2019 |
Mama Bird |
San Juan |
9 |
|
2019 |
Maple Rock |
San Juan |
0.75 |
|
2019 |
Tap Root |
San Juan |
0.25 |
|
2019 |
Well Fed |
Skagit |
2.75 |
|
2019 |
Wheel Herb |
Thurston |
N/A |
|
2020 |
Goose Foot |
San Juan |
0.25 |
|
2020 |
Mama Bird |
San Juan |
0.5 |
|
2020 |
Maple Rock |
San Juan |
0 |
|
2020 |
NWREC BL WW |
Skagit |
0 |
Results of trap cropping trial were analyzed across all site years. Total number of wireworms found in weekly core samples taken from treated area between row ranged from 2.2 for wheat and spinosad (WS) treatment to 0.44 for control (C). Treatments with wheat had significantly more total wireworms in the treated area, indicating that the wheat trap crop was acting as an effective attractant (Table 2). Percentage lettuce loss to wireworm feeding ranged from 31.8% in C plots to 16.8% in Wheat (W) treatment. Plots with wheat had significantly lower percentage loss of plants than the control (Table 2). Total lettuce yield was highly variable and likely impacted by other environmental factors, yields ranged from 231 g/plot in Control to 273 g/plot in WS treatment. There was no significant treatment effect for yield.
Table 2. 1Mean wireworms counted between lettuce rows in each plot over 6 week sampling period +/- standard deviation. 2Mean lettuce survival 4 weeks after transplanting +/- standard deviation. 3Mean lettuce yield calculated as grams per plot ± standard deviation. Letters indicate if treatments are significantly different from one another.
|
Treatment |
Total Wireworms1 |
Lettuce (% Survival)2 |
Lettuce Yield (g/m2)3 |
|
Control |
0.4+/-0.8 a | 31.9+/-35.6 b | 231.6+/-186.8 |
|
Spinosad |
0.8+/-1.1 ab | 28+/-37.6 ab | 257.3+/-195.5 |
|
2x Spinosad |
0.5+/-0.9 a | 26.9+/-34.4 ab | 245.8+/-188.3 |
|
Wheat |
2.2+/-4.2 b | 16.8+/-24.7 a | 273.4+/-209.8 |
|
Wheat + Spinosad |
2.2+/-4.2 b | 19.3+/-26.6 a | 273.5+/-189.9 |
|
2x Wheat |
1.8+/-2.9 b | 18+/-22.2 a | 238.6+/-136.4 |
|
2x Wheat + Spinosad |
1.8+/-3.5 b | 19.3+/-27.1 a | 239.5+/-166.9 |
|
|
|
|
|
|
p-value |
<0.0001 |
<0.0001 |
0.17 |
Across multiple environments trap cropping with wheat significantly decreased the loss of lettuce transplants. There was no difference between single and multiple wheat plantings. Application of Spinosad bait did not have a significant effect on lettuce loss. The effect of wheat is likely due to the attractant effect which allows the lettuce transplants to grow while the wireworms are feeding on wheat. Results indicate that planting wheat one week prior to transplanting vulnerable vegetables may effectively reduce loss of lettuce transplants, however it was not completely effective in eliminating wireworm damage.
Objective 2 Results and Discussion
2019
In spring of 2019 pheromone lures, pitfall traps and Instructions for monitoring adult Agriotes lineatus and Agriotes obscurus were distributed to project partners and volunteer WSU Master Gardeners representing 19 locations in 12 counties. Trapping occurred between the last week of May and the first week of July. Except one site that was monitored through mid September. Results confirmed presence of Agriotes spp. in 8 western Washington counties and no eastern Washington counties (Table 3).
Table 3. 2019 Click beetle monitoring locations, collection dates and numbers of Agriotes lineatus and Agriotes obscurus.
| County | First Collection Date | Last Collection Date | Days between first and last collection | Number of A. lineatus | Number of A. obscurus |
| Adams | 6/4/19 | 6/30/19 | 26 | 0 | 0 |
| Chelan | 6/3/19 | 7/2/19 | 29 | 0 | 0 |
| Chelan | 5/30/19 | 6/27/19 | 28 | 0 | 0 |
| Clallam | 6/4/19 | 6/30/19 | 26 | 63 | 0 |
| Cowlitz | 6/1/19 | 6/30/19 | 29 | 14 | 0 |
| Cowlitz | 6/3/19 | 6/24/19 | 21 | 1 | 0 |
| Grant | 5/31/19 | 6/28/19 | 28 | 0 | 0 |
| Grant | 5/29/19 | 6/26/19 | 28 | 0 | 0 |
| Grays Harbor | 5/29/19 | 7/11/19 | 43 | 103 | 0 |
| Jefferson | 5/29/19 | 6/30/19 | 32 | 74 | 0 |
| Kitsap | 6/13/19 | 6/13/19 | 0 | 0 | 0 |
| Kitsap | 5/28/19 | 6/25/19 | 28 | 13 | 0 |
| Skagit | 6/27/19 | 6/27/19 | 0 | 3 | 0 |
| Snohomish | 6/2/19 | 6/30/19 | 28 | 12 | 0 |
| Snohomish | 6/6/19 | 6/26/19 | 20 | 45 | 0 |
| Snohomish | 5/30/19 | 6/27/19 | 28 | 54 | 1 |
| Snohomish | 6/4/19 | 6/25/19 | 21 | 25 | 0 |
| Thurston | 5/29/19 | 6/25/19 | 27 | 42 | 0 |
| Whitman | 6/15/19 | 9/15/19 | 92 | 0 | 0 |
2020
In spring of 2020 pheromone lures, pitfall traps and instructions for monitoring adult Agriotes lineatus and Agriotes obscurus were distributed to project partners and volunteer WSU Master Gardeners representing 38 locations in 14 counties (Table 4). Trapping occurred between the last week of April and the last week of July. Building on the results from 2020 this survey confirmed presence of Agriotes spp. in multiple western Washington counties and no eastern Washington counties. It was also possible to maintain weekly collections at several sites which will provide information on timing of peak flights.
Table 4. 2020 Click beetle monitoring locations, collection dates and numbers of Agriotes lineatus and Agriotes obscurus.
| County | First Collection Date | Last Collection Date | Number of A. lineatus | Number of A. obscurus |
| Asotin | 5/5/20 | 6/30/20 | 0 | 0 |
| Asotin | 5/10/20 | 6/28/20 | 0 | 0 |
| Chelan | 5/30/20 | 6/27/20 | 0 | 0 |
| Grant | 5/8/20 | 7/1/20 | 0 | 0 |
| King | 5/6/20 | 7/1/20 | 524 | 133 |
| Kitsap | 5/10/20 | 7/22/20 | 836 | 0 |
| Lincoln | 5/12/20 | 6/29/20 | 0 | 0 |
| San Juan | 4/20/20 | 7/27/20 | 1587 | 0 |
| San Juan | 4/20/20 | 7/6/20 | 174 | 0 |
| San Juan | 4/30/20 | 7/6/20 | 1371 | 0 |
| San Juan | 5/14/20 | 7/9/20 | 7 | 0 |
| San Juan | 5/14/20 | 8/27/20 | 1346 | 0 |
| San Juan | 5/24/20 | 7/26/20 | 468 | 0 |
| Skagit | 4/22/20 | 7/29/20 | 1181 | 12 |
| Skagit | 5/11/20 | 7/29/20 | 419 | 2 |
| Snohomish | 5/3/20 | 8/2/20 | 657 | 0 |
| Snohomish | 5/8/20 | 6/26/20 | 97 | 0 |
| Snohomish | 5/11/20 | 7/7/20 | 397 | 53 |
2021
In 2021 a pheromone and trap for the native Limonius genus was added to the trapping locations. In total results were reported from 22 sites representing 13 counties (Table 5). Consistent with previous years no reports of Agriotes spp. were confirmed in Eastern Washington. Limonius species are present statewide and locally very abundant. In western Washington these genera occurred in the same locations indicating that multiple species of damage causing wireworms may be present. Additional lifecycle specific information may be needed to develop appropriate management methods for different species.
Table 5. 2021 Click beetle monitoring locations, collection dates and numbers of Agriotes lineatus, Agriotes obscurus and Limonius spp.
| County | First Collection Date | Last Collection Date | Number of A. lineatus | Number of A. obscurus | Number of Limonius spp. |
| Adams | 5/19/21 | 7/1/21 | 0 | 0 | 112 |
| Adams | 5/19/21 | 6/10/21 | 0 | 0 | 9 |
| Clallam | 5/14/21 | 6/30/21 | 2 | 0 | 173 |
| Clallam | 5/15/21 | 6/19/21 | 192 | 1 | 440 |
| Clark | 5/2/21 | 7/4/21 | 0 | 0 | 2654 |
| Clark | 5/5/21 | 7/2/21 | 2 | 0 | 171 |
| Grant | 6/14/21 | 7/12/21 | 0 | 0 | 1 |
| Grant | 6/21/21 | 7/12/21 | 0 | 0 | 0 |
| Grant | 6/23/21 | 7/14/21 | 0 | 0 | 0 |
| Island | 5/2/21 | 7/6/21 | 82 | 1 | 720 |
| Island | 5/12/21 | 6/29/21 | 84 | 0 | 4 |
| Jefferson | 5/14/21 | 7/26/21 | 584 | 1 | 5 |
| Kitsap | 4/1/31 | 7/6/21 | 7 | 0 | 72 |
| Kitsap | 5/11/21 | 6/29/21 | 103 | 0 | 193 |
| San Juan | 4/25/21 | 7/11/21 | 2632 | 48 | 1616 |
| San Juan | 4/27/21 | 5/11/21 | 311 | 1 | 3252 |
| San Juan | 5/6/21 | 6/30/21 | 890 | 0 | 208 |
| Skagit | 4/29/21 | 6/25/21 | 840 | 2 | 0 |
| Skagit | 6/10/21 | 7/1/21 | 17 | 65 | 0 |
| Snohomish | 5/30/21 | 7/31/21 | 310 | 3 | 0 |
| Thurston | 5/13/21 | 7/13/21 | 21 | 0 | 406 |
| Whatcom | 5/10/21 | 6/28/21 | 103 | 47 | 863 |
Research Outcomes
Education and Outreach
Participation Summary:
2018
Consultations
- Project personnel have consulted one-on-one with a minimum of 5 farmers and 5 agricultural professionals on wireworm management and distribution.
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 10 farmers.
Field Days
- Brouwer, B. and B. Gerdeman. July, 2018. Poster presentation at the Washington State University Northwest Washington Research and Extension Center Field Day. Reached 10 farmers and 10 ag professionals
Other
- San Juan County Fair - August 15- 18, 2018. Wireworm poster was displayed as part of the WSU Agricultural Tent.
Press Articles
- Project featured in Western IPM Center news article "Wireworms in Western Washington" and video written and produced by Steve Elliot has 925 views.
2019
Consultations
- Project personnel have consulted one-on-one with a minimum of 10 farmers and 5 agricultural professionals on wireworm management and distribution in 2019.
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 10 farmers.
Presentations
- Brouwer, B., B. Gerdeman, S. Bramwell, C. Looney, and T. Murray. Feb 16 2019. Managing Wireworms (Agriotes spp.) in Western Washington Organic Vegetable Crop Production. Organic Agriculture Research Forum, Portland, Oregon. Poster and Abstract. Reached 10 farmers and 15 ag professionals.
- Brouwer. B. March 4 2019. Wireworm Biology and Management. Whidbey Island Growers Association. Coupeville, WA. Reached 16 farmers.
- Brouwer, B and B. Gerdeman. Sep 19 2019. Wireworms: Lifecycle and Management in Organic Systems/ Gusanos de alambre: Ciclo de vida y gestión orgánica. Viva Farms. Mount Vernon, WA. Reached 15 farmers and 5 ag professionals.
- Brouwer, B. November 9 2019. Wireworm Monitoring and Management in Organic Vegetable Production. Tilth Conference. Yakima, WA. Reached 15 farmers.
- Brouwer, B.. August 14 2019. WSU Extension Research Updates. San Juan County Fair. Friday Harbor, WA. Reached 3 farmers.
Field Days
- Brouwer, B and B. Gerdeman. July 11 2019. Poster and table on wireworm management. NWREC Field Day. Mount Vernon, WA. ~10 farmers and ~10 ag professionals
- Brouwer, B., J. Post, and S. Bramwell. July 17 2019. Wireworm Field Day at The Wheel Herb Farm. Tumwater, WA. Reached 10 farmers and 3 ag professionals (25 total participants).
2020
Consultations
- Project personnel have consulted one-on-one with a minimum of 10 farmers and 5 agricultural professionals on wireworm management and distribution in 2020.
On-Farm Demonstrations
- Wireworm management trials were conducted on 4 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 8 farmers. Additionally, one management trial was established at the Washington State University Mount Vernon Northwest Research and Extension Center.
Presentations
- Brouwer, B.. February 21 2020. Wireworm (Agriotes spp.) lifecycle, monitoring and possible management. 38th Annual Western Washington Potato Workshop. Mount Vernon, WA. Reached 30 farms and 20 ag professionals
- Gerdeman, B. and B. Deihl. July 13 2020.Wireworm: Ultimate Foe. WSU Mount Vernon Brown Bag Webinar. Online. (116 views)
- Brouwer, B.. August 2020. Wireworms: Who they are, where they come from, what they eat, and how to discourage them. San Juan County Fair. Online. (25 Views)
Social Media
- Four Instagram posts on wireworm and click beetle research by @wsuextension_sjc had an average reach of 102.
2021
Consultations
- Project personnel have consulted one-on-one with a minimum of 10 growers and 5 agricultural professionals on wireworm management and distribution in 2021
Presentations
- Brouwer, B. July 7 2021. Wireworms: Lifecycle and Integrated Management Strategies. Virtual Dirt Talk hosted by Kitsap, Clallam and Jefferson County Extension Offices. Reached 36 farmers and 1 ag professional.
- Brouwer, B.. February 19 2021. Wireworm Research Update: Lifecycle, Distribution and Management. 39th Annual Western Washington Potato Workshop. Mount Vernon, WA. Reached 30 farmers and 16 ag professionals.
- Brouwer, B. July 8 2021. Distribution and management of wireworms in Western Washington organic vegetable production. 106th Annual Meeting and Professional Improvement Conference National Association of County Agricultural Agents. Virtual – Philadelphia. Reached 20 ag professionals.
2022
Consultations
- Project personnel have consulted one-on-one with a minimum of 5 farmers and 5 agricultural professionals on wireworm management and distribution in 2022.
Presentations
- Brouwer, B.. February 25 2022. Distribution and Management of Wireworms in western Washington. 40th Annual Western Washington Potato Workshop. Mount Vernon, WA. Reached 40 farmers and 20 ag professionals.
Education and Outreach Outcomes
Wireworm biology and life cycle
Identification of wireworms and damage
Methods for wireworm scouting
Trap cropping to manage wireworms
General strategies for wireworm management