Surveying the distribution of introduced wireworms in Washington State and evaluating trap cropping as a low-cost management option

Final report for OW18-018

Project Type: Professional + Producer
Funds awarded in 2018: $49,576.00
Projected End Date: 03/31/2022
Grant Recipient: Washington State University Extension
Region: Western
State: Washington
Principal Investigator:
Dr. Brook Brouwer
Washington State University Extension
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Project Information

Abstract:

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.

Project Objectives:

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

Click linked name(s) to expand/collapse or show everyone's info
  • Todd Murray (Educator and Researcher)
  • Dr. Beverly Gerdeman (Educator and Researcher)
  • Stephen Bramwell (Educator and Researcher)
  • Christopher Looney (Educator and Researcher)

Research

Materials and methods:

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:

  1. 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
  2. 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. 
  3. Lettuce (cv 'Muir') was be grown from seed in 72 cell trays for three to four weeks prior to transplanting. 
  4. 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.  
  5. 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.
  6. 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:

  1. Lettuce mortality in each plot was recorded weekly following transplanting.
  2. 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. 
  3. 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. 

  1. 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.
  2. 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.
  3. Traps were deployed in established grassland areas from approximately April to July. 
  4. Pheromone traps were monitored weekly to determine number and species of adult males attracted to the pheromone lures. 
  5. Samples were collected and frozen for project team members to count and confirm species identification. 
Research results and discussion:

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

 

Participation Summary
12 Farmers participating in research

Educational & Outreach Activities

65 Consultations
1 Curricula, factsheets or educational tools
16 On-farm demonstrations
1 Published press articles, newsletters
12 Webinars / talks / presentations
3 Workshop field days
1 Other educational activities: San Juan County Fair Display in 2018

Participation Summary:

283 Farmers
145 Ag professionals participated
Education/outreach description:

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

 

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.

 

Learning Outcomes

55 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • Wireworm biology and life cycle

  • Identification of wireworms and damage

  • Methods for wireworm scouting

  • Trap cropping to manage wireworms

  • General strategies for wireworm management

Project Outcomes

51 Farmers intend/plan to change their practice(s)
2 New working collaborations
Project outcomes:

Organic control of wireworms remains a persistent challenge in western Washington, however this project contributed to improved knowledge of pest lifecycle, distribution and management. Through our out reach we increased knowledge and provided farmers with information they plan to implement on their farms which in the long term will contribute to the sustainability of crop production in the region. 

Project Objective #1 involved the evaluation of a trap cropping method and an insecticide bait, to reduce damage in transplanted lettuce.  Our work demonstrated that trap cropping was effective in reducing loss at sites with high wireworm pressure. The insecticide was not found to be effective. Reducing unnecessary pesticide applications will reduce costs, as well as potential environmental damage. Demonstrating the effectiveness of trap cropping gives growers another tool for management, as well as with information to assess the effectiveness relative to other methods. This management information has the potential to reduce loss of organic vegetable crops as well as improve cost effectiveness of pest management. 

Through project Objective #2 we were able to increase knowledge of when click beetles (adult form of wireworms) fly and lay eggs, which is a critical component of long term management strategy. We also documented distribution of introduced Agriotes spp. in nearly all western Washington counties, with no reports from eastern Washington. Basic understanding of pest biology and distribution is foundational for future development of sustainable management strategies. 

Participants in outreach events reported increased knowledge and plan to utilize information gained to improve pest identification, avoiding high risk cropping systems and use an integrated approach to management. The outcomes of this project will continue to improve sustainability of organic crop production in western Washington. 

Success stories:

This project contributed to the development of an international collaboration with researchers at Agriculture and Agri-Food Canada.  They provided newly developed pheromone lures and were able to leverage our monitoring network to include an additional genera of wireworm which has not been widely studied in our region.  This collaboration contributed to basic understanding of pest species distribution which is critical for designing effective management tools for sustainable crop production.  Prior to our work there was very limited information on relative abundance of different wireworm species in western Washington. 

 

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.