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

Progress 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
  • 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 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).  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). Over the two years (2018-2019) 10 grower cooperators have hosted trials and been 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 'Mirlo') 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. 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
  2. Distribute pheromone traps developed for Agriotes obscures and Agriotes lineatus to Master Gardeners and other WSU Extension volunteers across the state
  3. Deploy traps in established grassland near or in agricultural production areas.
  4. Monitor pheromone traps weekly to determine number and species of adult males attracted to the pheromone lures.
  5. Process samples and confirmation of species identification by WSDA entomologists.
Research results and discussion:

Objective 1 Results and Discussion

2018 Results

Table 1. Presence of wireworms (Agriotes spp.) in wheat bait traps after 1 week.

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
2018 Skagit Skagit Flats 0
2018 Skagit Viva Farms 0
2018 Thurston Calliope Farm 0

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 Agriotes spp.

Agriotes spp. wireworms were found in bait traps at 3 of the farm sites (Table 1). Subsequent analysis was conducted using data from these sites. Treatment was significant for total wireworms found between the lettuce rows, lettuce survival at four weeks after transplanting and final lettuce yield (Table 2). All treatments using wheat as a trap crop were significantly different from the control. None of the spinosad alone treatments were significantly different from the control.

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 meter squared ± standard deviation. *p-value <0.05, **p-value <0.01, ***p-value <0.001 significantly different from control based on Dunnett test.

Treatment

Total Wireworms1

Lettuce      (% Survival)2

Lettuce Yield (g/m2)3

Control

1 ± 1

17 ± 22

29 ± 48

Spinosad

2 ± 1

19 ± 24

32 ± 66

2x Spinosad

1 ± 1

25 ± 19

45 ± 71

Wheat

7 ± 7***

50 ± 25**

69 ± 63**

Wheat + Spinosad

7 ± 7***

47 ± 22**

65 ± 68*

2x Wheat

5 ± 4***

53 ± 16***

77 ± 58**

2x Wheat + Spinosad

8 ± 5***

41 ± 23*

56 ± 60*

 

 

 

 

p-value

<0.0001

<0.0001

<0.0001

2019

Table 3. Presence of wireworms (Agriotes spp.) in wheat bait traps after 1 week.

Year County Farm Average Wireworms/ Bait Trap
2019 San Juan Maple Rock .75
2019 San Juan Tap Root .25
2019 San Juan Mama Bird 9
2019 Skagit Well Fed Farm 2.75
2019 Island Deep Harvest 0
2019 Thurston Wheel Herb 10.5

 

2020

Table 4. Presence of wireworms (Agriotes spp.) in wheat bait traps after 1 week.

Year County Farm Average Wireworms/ Bait Trap
2020 Skagit NWREC 0
2020 San Juan  Mama Bird 0.5
2020 San Juan  Maple Rock 0
2020 San Juan  Goose Foot 0.25

 

Results for 2019 and 2020 management trials are being analyzed. Trials were conducted at 7 trial locations listed above.  In 2020 the Thurston County trial site was modified to replace the lettuce crop with potatoes. Wireworm counts were lower in 2020 at most sites, potentially impacting our ability to determine treatment effects. 

 

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 5. 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. 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 6. 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
Participation Summary
12 Farmers participating in research

Educational & Outreach Activities

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

Participation Summary:

274 Farmers
58 Ag professionals participated
Education/outreach description:

Outreach to Date

2018

Consultations

  • Project personnel have consulted one-on-one with a minimum of 5 growers 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 at least 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. ~10 farmers and ~10 ag professionals

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 growers 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 at least 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. ~10 farmers, ~15 ag professionals
  • Brouwer. B. March 4 2019. Wireworm Biology and Management. Whidbey Island Growers Association. Coupeville, Wa. ~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. ~15 farmers, ~5 ag professionals

  • Brouwer, B. November 9 2019. Wireworm Monitoring and Management in Organic Vegetable Production. Tilth Conference. Yakima, WA. 15 farmers.

  • Brouwer, B.. August 14 2019. WSU Extension Research Updates. San Juan County Fair. Friday Harbor, WA. 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. 25 attendees (10 farmers, 3 ag professionals)

2020

Consultations

  • Project personnel have consulted one-on-one with a minimum of 10 growers 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. (~50 participants)
  • Gerdeman, B. and B. Deihl. July 13 2020.Wireworm: Ultimate Foe. WSU Mount Vernon Brown Bag Webinar. Online. (57 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. 

Learning Outcomes

20 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

19 Farmers intend/plan to change their practice(s)
2 New working collaborations
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.