Biological and Cultural Tactics for the Control of Wireworms in Root Crops

Progress report for LNE20-400

Project Type: Research and Education
Funds awarded in 2020: $116,189.00
Projected End Date: 04/30/2023
Grant Recipient: University of Vermont
Region: Northeast
State: Vermont
Project Leader:
Victor Izzo
University of Vermont
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Project Information

Summary:

 

Problem and Justification

For diversified vegetable farmers, wireworms represent a significant pest as they exhibit an extensive host range including a variety of popular root vegetables (e.g. radishes, potatoes, sweet potatoes, etc.) and grass-based cash crops (e.g. corn.) Feeding injury from wireworms can quickly reduce the marketability of root crops as even limited damage can result in higher disease incidence and reduced consumer value. Because root crops represent a large proportion of the harvested storage crops in the northeast, wireworms are particularly concerning for growers. According to the National Agricultural Statistics Service (NASS) sweet potato production in the USA has increased 6.1% per year since 2000 (23).

Solution and Approach

This project will investigate strategies to best prepare root crop growers for wireworm infestations and reduce the likelihood of significant wireworm pressure in root crop plantings. The primary educational program will focus on assessing grower level of knowledge and familiarity with wireworms in root crops and the currently available tactics for their management in temperate agroecosystems. Learning outcomes for this curriculum will be divided into two general categories: knowledge building and skill development. To best support growers our project looks to develop a robust wireworm educational program in conjunction with a research plan to explore novel tactics to better manage wireworm pressure in sweet potato crops. Specifically, our project will perform three sets of field trials to test different pest management tactics for wireworm management. These avenues of research will include: the use of entomopathogenic fungi for biological control, high glucosinolate mustard (HGM) biofumigation, and the development of a cover crop ranking system to identify the most problematic cover crops for wireworm recruitment.

Milestones and Performance Target

Northeastern diversified vegetable farmers are the primary beneficiaries of this project. Particularly, we will focus our efforts on farmers with a significant investment in root crops, and utilizing grass cover crops in their rotation schedule. By the end of this project, Seventy-five northeastern vegetable growers will acquire advanced knowledge of wireworm ecology and the use of novel management tactics for the control of wireworms. Application of this knowledge will occur on 50 acres of planted root crops protecting $225,000/year worth of root crops. Of these seventy-five growers, ten will report their estimated average recovery of losses. 

Performance Target:

Seventy-five Northeastern growers will each apply at least one novel management tactic for the control of wireworms on a total of 75 acres of root crops. 50 of these farmers producing $225,000 worth of root crops annually will report a reduction in crop losses to wireworms compared to previous years.

 

Introduction:

For diversified vegetable farmers, wireworms represent a significant pest as they exhibit an extensive host range including a variety of popular root vegetables (e.g. radishes, potatoes, sweet potatoes, etc.) and grass-based cash crops (e.g. corn.) Feeding injury from wireworms can quickly reduce the marketability of root crops as even limited damage can result in higher disease incidence and reduced consumer value. Because root crops represent a large proportion of the harvested storage crops in the northeast, pests associated with these crops are particularly concerning for growers. According to the National Agricultural Statistics Service (NASS) sweet potato production in the USA has increased 6.1% per year since 2000 (USDA NASS, 2017). This growth is underscored by the current estimated national economic value of sweet potato harvests, ~$650 million USD (USDA NASS, 2017.) In the northeast region alone, sweet potato production covers close to 1500 acres (~$7 million value). Given the high vulnerability of sweet potato plantings to wireworm pressure, even a conservative estimate (e.g 10-20%) of marketable losses would result in a ~$700K reduction in economic value. 

This project will investigate strategies to best prepare root crop growers for wireworm infestations and reduce the likelihood of significant wireworm pressure in root crop plantings. The primary educational program will focus on assessing grower level of knowledge and familiarity with wireworms in root crops and the currently available tactics for their management in temperate agroecosystems. Learning outcomes for this curriculum will be divided into two general categories: knowledge building and skill development. Growers participating in our educational program will receive detailed and practical knowledge on a variety of relevant topics focused on wireworm ecology and currently available tactics. Te best support skills development, growers will be trained in the proper deployment of various low-impact and ecologically based IPM tactics for wireworm management. Though comprehensive in nature, these training will pay particular attention to cultural and biological control tactics including those tested in our field trials. Webinars, research site field days, individual and remote consultations, and extension workshops (beginning in year 2) will directly support our educational curriculum.

For the research portion of our project, we will perform three sets of field trials to test different pest management tactics for wireworm management. These avenues of research will include: the use of entomopathogenic fungi for biological control, high glucosinolate mustard (HGM) biofumigation, and the development of a cover crop ranking system to identify the most problematic cover crops for wireworm recruitment. With a mix of cultural (i.e. cover crops) and biological control (i.e. EPFs) tactics the outcomes of our trials will provide farmers with adaptable and affordable low-tech options for managing wireworms. Furthermore, the development of non-chemical options potentially reduces the use (and cost) of chemical control options  and subsequently lowers the risk of pesticide resistance. 

 

 

Cooperators

Click linked name(s) to expand
  • Scott Lewins (Educator and Researcher)
  • Dr. Heather Darby (Researcher)

Research

Hypothesis:

Hypothesis I: Cover crop types will significantly differ in their recruitment of wireworms and their subsequent effect on sweet potato marketability. 

Hypothesis II: Soil application of Metarhizium anisopliae will significantly affect the incidence of root damage in sweet potatoes and the marketability of fresh market sweet potato tubers.

Hypothesis III: High glucosinolate mustard biofumigation will significantly affect pest pressure associated with wireworm infestations in sweet potato plantings.

Materials and methods:

The following research objectives are the product of an ongoing Participatory Action Research (PAR) project whereby participating growers identified their most preferred areas of research on wireworms. Provided this information, we chose field trials to test the three most popular suggestions:

  • To identify the tradeoffs associated with the use of different cover crops in relation to wireworm damage, soil nutrients and yield (originally proposed by Andy Jones – Intervale Community Farm).
  • To test the efficacy of an entomopathogenic fungus, Metarhizium anisopliae, as a biological control agent of wireworms (originally proposed by Becky Maden – Singing Cedars Farm).
  • To test the efficacy of high glucosinolate mustard crops as a biofumigant for the reduction of wireworm pressure (originally proposed by Jon Wagner – Bear Roots Farm).   

Hypothesis I: Cover crop types will significantly differ in their recruitment of wireworms and their subsequent effect on sweet potato marketability.  

Treatments: Experimental treatments at three commercial farms and two experimental farms include two commonly used grass species cover crops – rye and oats. 

Methods: We are conducting field trials on two UVM-associated research farms – Catamount Farm at the UVM Horticultural Research and Education Center in South Burlington, VT and Borderview Research Farm in Alburgh, VT. In addition, on-farm trials are being conducted at three commercial diversified farms that experience wireworm damage in their root crops – Intervale Community Farm in Burlington, VT, Singing Ceders Farm in Orwell, VT, and Israeli Harvest in West Haven, VT.

We employed a split plot design, such that at all five locations, half of the field was randomly assigned to each cover crop treatment. In mid-September (2020 and 2021) cover crops were/will be drilled: rye at 100 lbs/acre, and oats at 100lbs/acre. The following spring the fields will be plowed, disked, and fertilized. At the research farms a 100ft long x 40in wide bed will be formed, and black plastic and drip tape for irrigation will be laid perpendicular to cover crop seeding, thus each bed will be across all cover crop treatments (see attached plot diagram). Covington variety sweet potato slips will be planted, with 2 rows per bed and 1 foot spacing within rows, in mid-to-late June (Summer 2021 and 2022). Specific horticultural practices (e.g. bed prep, plant spacing, etc.) at each commercial farm site will be based on their own best practices, thus will vary from each other and differ from the research farms. 

Data Collection and Analysis: We will randomly subsample 100 sweet potatoes from each subplot (previously cover cropped bed portions) and collect larval damage (number of wireworm mines) and marketable yield (lbs) data. We will also trap wireworms to confirm their presence and identify the species. For statistical analysis, damage incidence and marketable yields will be designated as dependent variables, and differences among treatments will be determined via a generalized linear model for both dependent variables. Cover crop treatment will be considered the single fixed factor. Farm site, trial year and their associated interactions will be considered random effects.

Farmer Input: This research question was originally proposed by Andy Jones of Intervale Community Farm.  Andy is consistently inundated with wireworms, and yet, he is also committed to using cover crops for their soil health benefits.  Given this conundrum, Andy helped us to develop research trials to explore the differences among different grass cover crops relevant for his commercial production. He will host field trial and serve on our advisory committee.

 

Hypothesis II: Soil application of Metarhizium anisopliae will significantly affect the incidence of root damage in sweet potatoes and the marketability of fresh market sweet potato tubers.

Treatments: Experimental treatments will include plots treated with Metarhizium compared to untreated controls.

Methods: We will conduct field trials on the same two research farms mentioned above. Fields that were previously been in sod (in order to maximize the likelihood of wireworm recruitment in field plots) will be plowed in with a moldboard plow, disked, and fertilized using Pro Grow. A 100ft long x 40in wide bed will be formed, black plastic and drip tape for irrigation will be laid, and sweet potatoes will be planted in mid-to-late June (2021 and 2022) as described above. We will use a Randomized Complete Block Design where treatments will be randomly assigned to 20bdft long plots (see attached plot diagram). There will be five untreated control plots and Met 52 EC (Novozymes Biologicals Inc., Salem, VA) will be applied as a soil drench at 2qts/acre to five experimental plots. 

Data Collection and Analysis: We will harvest sweet potatoes from 20 plants in each plot, collect larval damage and marketable yield data, and conduct the same statistical analysis. Metarhizium treatment will be considered the single fixed factor, with farm site, block, trial year and their associated interactions considered random effects.

Farmer Input: This research question was originally proposed by Becky Maden of Singing Cedars Farm, Orwell, VT and UVM Extension. Becky has suggested the most appropriate treatments to test, aided in the development of the protocol such that it is compatible to her scale, and will serve on the advisory committee.

 

Hypothesis III: High glucosinolate mustard biofumigation will significantly affect pest pressure associated with wireworm infestations in sweet potato plantings.

Treatments: Experimental treatments will include plots biofumigated with HGM compared to untreated controls. 

Methods: We will conduct field trials on the same two research farms mentioned above, and again we will use a Randomized Complete Block Design. Randomly assigned 20bdft long plots will be planted as either untreated controls or experimental treatments of HGM. In the HGM plots, Trifecta Power Blend (Mighty Mustard, PNW Co-op Spokane Valley, WA) will be broadcasted at 12lbs/acre and incorporated on April 15 (2021 and 2022), and allowed to grow for 60 days to allow for the accumulation of sufficient biomass. On on June 15 it will be terminated using a brush hog, incorporated immediately using disc harrows, and then tarped. Tarps will remain on the plots for 2 weeks to allow the HGM to breakdown, releasing the glucosinolates, and fumigate the soil. A 100ft long x 40in wide bed will be formed, and black plastic and drip tape for irrigation will be laid, encompassing the five plots control plots and five experimental plots (see attached plot diagram). Covington variety sweet potato slips will be planted, with 2 rows per bed and 1 foot spacing within rows, in mid-to-late June (2021 and 2022).

Data Collection and Analysis:

We will harvest sweet potatoes from 20 plants in each plot, collect larval damage and marketable yield data, and conduct the same statistical analysis described above.  HGM treatment will be considered the single fixed factor, with farm site, block, trial year and their associated interactions considered random effects.

Farmer Input:

This research question was originally proposed by Jon Wagner of Bear Roots Farm in Williamstown, VT. Jon has struggled with wireworms in his root crops and is interested using low-tech solutions like biofumigant cover crops. To best suit his growing schedule he helped our team develop the protocol to fit his scale, and has offered to host a field trial and serve on the advisory committee.

Research results and discussion:

There are no results to report at this point. We have planted our cover crop treatments and will be beginning our field trials and assessments this upcoming field season (as detailed in our methods above). Our data will be collected over the course of the 2021 and 2022 growing seasons.

Research conclusions:

There are no conclusions to report at this point, conclusions will be made after the 2021 and 2022 growing seasons

Participation Summary
10 Farmers participating in research

Education

Educational approach:

82 growers and over 20 agricultural service providers across Vermont, New Hampshire, Maine, Massachusetts, Connecticut, Rhode Island, and New York have been erolled in our education program to date. Our educational curriculum will focus upon adaptable information to aid farmers in applying sustainable IPM tactics both new and old for the management of wireworms in susceptible root crops. Learning outcomes for this curriculum will be divided into two general categories: knowledge building and skill development.

Knowledge Building: Growers participating in our educational program will receive detailed and practical knowledge on a variety of relevant topics. These topics shall include: 1) the ecology and biology of wireworms in vegetable cropping systems; 2) cultural control tactics for wireworm management; 3) ecological considerations for biological control applications; 4) descriptions of the general biology and mode of actions for several biologically based IPM tactics including HGM fumigation (tested in this project), Entomopathogenic fungi (tested in this project) and Entomopathogenic nematodes; 5) any results stemming from our research trials.

Skills Development: Growers will be trained in the proper deployment of various low-impact and ecologically based IPM tactics for wireworm management. Though comprehensive in nature, these training will pay particular attention to cultural and biological control tactics including those tested in our field trials. Farm demonstrations and field days at our experimental sites will provide growers the opportunity to directly observe the basic protocols for assessing wireworm presence and damage, choosing suitable control strategies and effective execution of chosen tactics. These field day presentations will be digitally recorded for wider distribution.

Milestones

Milestone #1 (click to expand/collapse)
What beneficiaries do and learn:

Northeastern vegetable growers (from NY, NH, VT, MA, CT, PA, NJ and ME) will receive a survey distributed with the assistance of agricultural service providers in each state. These surveys will look to assess general wireworm knowledge, vulnerability, currently used tactics and interest in adopting new practices including those being tested in the research portion of this project. Four solicitations in the first year (2020) - June, Aug, Sept, Nov;

Proposed number of farmer beneficiaries who will participate:
150
Proposed number of agriculture service provider beneficiaries who will participate:
8
Actual number of farmer beneficiaries who participated:
82
Actual number of agriculture service provider beneficiaries who participated:
20
Proposed Completion Date:
November 30, 2020
Status:
In Progress
Accomplishments:

During this past season (2020), our research team reached out to our own network of growers and enlisted the support of other extension service providers to distribute a streamlined survey to gauge interest in our educational program.  

Milestone #2 (click to expand/collapse)
What beneficiaries do and learn:

Growers will return the survey and will agree to participate in an education and outreach program addressing wireworms, available biocontrol and HGM fumigation suppliers, including webinars and/or consultations.

Proposed number of farmer beneficiaries who will participate:
50
Proposed number of agriculture service provider beneficiaries who will participate:
2
Proposed Completion Date:
April 30, 2021
Status:
In Progress
Milestone #3 (click to expand/collapse)
What beneficiaries do and learn:

Participating growers and UVM's Horticultural Research and Education Center will host field days in consecutive years detailing the project on both commercial and research farms. Growers attending the field days will gain practical insight into the knowledge, resources and skills necessary to successfully apply wireworm management tactics.

Proposed number of farmer beneficiaries who will participate:
43
Proposed number of agriculture service provider beneficiaries who will participate:
2
Proposed Completion Date:
September 1, 2022
Status:
In Progress
Milestone #4 (click to expand/collapse)
What beneficiaries do and learn:

We will present research updates at consecutive Summer Northwest Crops and Soils Field days in VT (2021/2022). These info sessions will provide up to 100 (50/year) growers the most up to date information on our research.

Proposed number of farmer beneficiaries who will participate:
100
Proposed number of agriculture service provider beneficiaries who will participate:
30
Proposed Completion Date:
September 1, 2022
Status:
In Progress
Milestone #5 (click to expand/collapse)
What beneficiaries do and learn:

Six high risk growers will receive personalized remote or on-farm consultations to assess the best course of possible action (for the following season) on their farms to reduce the impact of wireworms in sweet potatoes.

Proposed number of farmer beneficiaries who will participate:
6
Proposed number of agriculture service provider beneficiaries who will participate:
2
Proposed Completion Date:
September 30, 2022
Status:
In Progress
Milestone #6 (click to expand/collapse)
What beneficiaries do and learn:

Updates on the research trials will be distributed at the end of each field season to all growers participating in the educational program and on regional listserves. The yearly distributions will provide growers ample time to adopt the new tactics or make plans for the implementation of the tactic in the following season. These updates will increase the likelihood that farmers will participate in the verification surveys to properly assess the project's success.

Proposed number of farmer beneficiaries who will participate:
50
Proposed number of agriculture service provider beneficiaries who will participate:
3
Proposed Completion Date:
December 30, 2022
Status:
In Progress
Milestone #7 (click to expand/collapse)
What beneficiaries do and learn:

Growers attending the annual Northeast NOFA Winter Conferences, Eastern NY Fruit & Vegetable Conference, Mid-Atlantic Veg and Berry Convention, VT Veg and Berry Winter Conference and the New England Vegetable & Fruit Conference will participate in info sessions and workshops detailing our research in consecutive years (WInter 2022/2023).

Proposed number of farmer beneficiaries who will participate:
250
Proposed number of agriculture service provider beneficiaries who will participate:
50
Proposed Completion Date:
February 28, 2023
Status:
In Progress
Milestone #8 (click to expand/collapse)
What beneficiaries do and learn:

The final verification surveys will be distributed following the final field season. They will be disseminated on regional listserves and other networks developed over the course of the grant to evaluate knowledge of the pest, the regional adoption rate of new practices and success of the tactics.

Proposed number of farmer beneficiaries who will participate:
150
Proposed number of agriculture service provider beneficiaries who will participate:
10
Proposed Completion Date:
March 30, 2023
Status:
In Progress
Milestone #9 (click to expand/collapse)
What beneficiaries do and learn:

Growers committed to implementing any of the new tactics being tested in our research trials will be provided with one-on-one support (e.g. email, webinars, on-farm consultations, etc.) as they implement new tactics

Proposed number of farmer beneficiaries who will participate:
10
Proposed Completion Date:
August 26, 2022
Status:
In Progress

Milestone Activities and Participation Summary

1 Enrollment in education program through either direct email contact or through filling out our online survey

Participation Summary

82 Farmers
20 Number of agricultural educator or service providers reached through education and outreach activities

Performance Target Outcomes

Target #1

Target: number of farmers:
75
Target: change/adoption:

Northeastern growers will acquire and apply the advanced knowledge of wireworm biology, ecology and the use of novel management tactics for the control of wireworms in root crops.

Target: amount of production affected:

Application of this knowledge will occur on up to 50 acres of sweet potato cropland

Target: quantified benefit(s):

Protecting $225,000/year worth of sweet potatoes from wireworm damage. Of these seventy-five growers, ten will report their estimated average recovery of losses.

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.