Final report for LNE20-400
Project Information
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 investigated 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 focused 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 the curriculum was divided into two general categories: knowledge building and skill development. To best support growers our project looked to develop an educational program in conjunction with a research plan to explore novel tactics to better manage wireworm pressure in sweet potato and potato crops. Specifically, our project performed three sets of field trials to test different pest management tactics for wireworm management. These avenues of research included: 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.
Research Results:
Key Conclusions and Recommendations from the Research Results:
- The application of Metarhizium anisopliae and other biorational soil drenches did not effectively reduce wireworm damage in sweet potatoes in some cases and even increased wireworm pressure in others. Farmers should be cautious when considering the use of these specific treatments until their efficacy is further evaluated.
- Biorational soil drenches, including entomopathogenic fungi, did not affect wireworm pressure in the 2021 field season. Farmers may need to exercise caution when considering the use of biorational soil drenches for wireworm control until further research provides more conclusive evidence of their efficacy.
- Rye cover crop treatments exhibited reduced wireworm pressure in sweet potatoes compared to oat cover crops in the 2022 field season. This trend was consistent at commercial farm sites. Farmers should consider using rye cover crops to mitigate wireworm damage in sweet potato plantings.
- Biopesticide trials with entomopathogenic fungi were inconclusive due to an absence of wireworm pressure at the research farms in the 2022 field season. Further research and testing may be needed to assess the effectiveness of biopesticides for wireworm management.
- High glucosinolate mustard (HGM) biofumigation showed significant reduction in wireworm pressure in sweet potatoes compared to no cover crop control. Farmers are recommended to consider implementing HGM biofumigation to manage wireworm infestations in sweet potato plantings.
Overall, the research suggests that implementing high glucosinolate mustard biofumigation and rye cover crop treatments can be beneficial for managing wireworm pressure in sweet potato plantings. Farmers should consider these strategies as potential tactics for reducing wireworm damage and protecting their crop yields.
Milestones
Northeastern diversified vegetable farmers were the primary beneficiaries of this project. Particularly, we focused 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, roughly 48 northeastern vegetable growers acquired advanced knowledge of wireworm ecology and the use of novel management tactics for the control of wireworms through our educational program. Direct application of this knowledge was difficult to estimate in the form of reduced damage estimates but 5 growers out of our educational program indicated that the knowledge generated from our research and educational program will be utilized for managing wireworm in their root cropping systems.
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.
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 investigated 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 focused 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 were divided into two general categories: knowledge building and skill development. Growers participating in our educational program received detailed and practical knowledge on a variety of relevant topics focused on wireworm ecology and currently available tactics. The best support skills development, growers were provided information on the proper deployment of various low-impact and ecologically based IPM tactics for wireworm management. Though comprehensive in nature, the training paid 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 looked to directly support our educational curriculum.
For the research portion of our project, we performed three sets of field trials to test different pest management tactics for wireworm management. These avenues of research included: 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 provided farmers with adaptable and affordable low-tech options for managing wireworms. Furthermore, the development and investigation of non-chemical options can support growers in reducing the use (and cost) of chemical control options and subsequently lower the risk of pesticide resistance.
Cooperators
- (Educator and Researcher)
- (Researcher)
Research
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.
The following research objectives were 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 conducted 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 were 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.
During field season 2021 we planted three different cover crops to assess their affect of wireworm pressure: Oat, Winter Rye, and High Glucosinolate Mustard. The trials were replicated on five farms in the northwest region of Vermont: West Haven, Burlington, South Burlington, and Alburgh and Orwell. Both Burlington and Allburgh site are University farms and the third site in Burlington was located at the Intervale Community Farm. We did not test the HGM treatment only at the UVM research farms research sites . We estimated wireworm damage by the number of wireworm galleries/per sweet potato. Twenty sweet potatoes were selected from each plot.
Data Collection and Analysis: We randomly subsampled 20 sweet potatoes from each subplot (previously cover cropped bed portions) and collected larval damage (number of wireworm mines). For statistical analysis, damage incidence was designated as the primary dependent variable, and differences among treatments were be determined via a generalized linear model. Cover crop treatment was considered the single fixed factor. Farm site, trial year and their associated interactions were considered random effects.
Farmer Input: This research question was originally proposed by Andy Jones of Intervale Community Farm. Andy was a consultant throughout the project on these specific trials.
Hypothesis II: Soil application of Metarhizium anisopliae and other biological controls will significantly affect the incidence of root damage in sweet potatoes and the marketability of fresh market sweet potato tubers.
Treatments: Experimental treatments included plots treated with Metarhizium and other biological controls and were compared to untreated controls.
Methods: Fields that were previously been in sod (in order to maximize the likelihood of wireworm recruitment in field plots) were 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 used a Randomized Complete Block Design where treatments were randomly assigned to 20bdft long plots (see attached plot diagram).
The treatments and their primary biological control element were the following: Metarhizium (fungus on grain) = met-home; Beuavaria (fungus) = Botega; Grain control = Grain; Entomopathogenic Nematodes (three species)= nematodes; spinosad (insect bait) = seduce
These treatments were applied at three farms: UVM Horticultural Research Farm, UVM Research Farm Borderview, and Intervale Community Farm.
Data Collection and Analysis: We harvested sweet potatoes from 20 plants in each plot, collected larval damage, and conducted the same statistical analysis. Metarhizium treatment was 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 suggested the most appropriate treatments to test and aided in the execution of the trials.
Hypothesis III: High glucosinolate mustard biofumigation will significantly affect pest pressure associated with wireworm infestations in sweet potato plantings.
Treatments: Experimental treatments included plots biofumigated with HGM compared to untreated controls.
Methods:
Field Trial
To test this hypothesis, we conducted a field trial at Bear Root Farm, Williamstown, VT, comparing plots biofumigated with high glucosinolate mustard (HGM) to untreated control plots. We seeded Trifecta Power Blend (Mighty Mustard, PNW Co-op Spokane Valley, WA) at a rate of 12 lbs/acre and incorporated it on April 25th, 2023, allowing for 30 days of growth to accumulate sufficient biomass. On May 25th, 2023, the mustard plants were mowed and then tarped, with the tarps remaining on the plots for 2 weeks to facilitate the breakdown of HGM, release of glucosinolates, and fumigation of the soil. A 100 ft long x 40 in wide bed was established, with half planted with mustard and the other half left without a cover crop. Black plastic and drip tape for irrigation were laid, and Covington variety sweet potato slips were planted on June 1st, with 2 rows per bed and 1-foot spacing within rows.
Harvest and Data Analysis
A total of 250 sweet potatoes were harvested from the HGM and control plots on October 15th, 2023, and were subsequently evaluated for larval damage and marketable yield data. Our data exhibited a non-normal distribution pattern, as determined by the Shapiro-Wilk normality test (p-value < 0.05). To address this, a non-binomial generalized model was utilized to account for the outliers and non-normal distribution, enabling us to analyze potential differences between the HGM treatment and control
Farmer Input:
This research question was originally proposed by Jon Wagner of Bear Roots Farm in Williamstown, VT. To best suit his growing schedule he helped our team develop the protocol to fit his scale for proper execution.
Key Findings for the 2023 field season:
- High glucosinolate mustard biofumigation treatments exhibited reduced wireworm pressure in sweet potatoes when compared with no cover crop control.
Hypothesis III: High glucosinolate mustard biofumigation will significantly affect pest pressure associated with wireworm infestations in sweet potato plantings.
The results of the non-binomial regression analysis for the treatments at Bear Root Farm are presented in Table 1. Specifically, the number of galleries in the control group was found to be significantly different (lower) from those in the HGM-treated plots (see Table 1). Additionally, Figures 2A and 2B illustrate the severity and incidence percentage of wireworm damage in the HGM-treated plots and the control, with the findings indicating a significant reduction in wireworm damage on sweet potatoes as a result of HGM treatment.
Table 1. Non-binomial regression analysis
A)
B)
Field Season 2022:
Key Findings for the 2022 field season:
- Rye cover crop treatments exhibited reduced wireworm pressure in sweet potatoes when compared with oat cover crops. This trend was documented at all of the commercial farm sites.
- Biopesticide trials at the two research farms, Horticultural Research and Education Farm were inconclusive due to an absence of wireworm pressure at both sites.
Hypothesis I: Cover crop types will significantly differ in their recruitment of wireworms and their subsequent effect on sweet potato marketability.
Wireworm Damage (Severity)
Sweet potato plots planted following rye cover crop (green) exhibited significantly less wireworm "galleries" per sweet potato than those plots following oat cover crop (yellow). Intervale Community Farm displayed the highest mean wireworm pressure (>15 galleris/potato) and was the only farm to show significant differences between the two cover crop treatments. However, similar trends were seen at all three commercial farms.
Wireworm Damage (Incidence)
Sweet potato plots following rye cover crop (green bars), on average, displayed fewer incidences of wireworm larval feeding when compared with plots following oat cover crop (yellow bars). Though these differences were not statistically significant, a similar trend was documented at each farm.
Key Findings for the 2021 field season:
- Biorational soil drenches including entomopathogenic fungi did not affect wireworm pressure
- Cover crop treatments of oats and rye exhibited opposing outcomes on the two farms where wireworm pressure reached high enough levels to estimate statistical differences.
Hypotheses I & III (Cover crops)
Due to the low levels of wireworm pressure at Singing Cedars (Orwell), UVM Horticultural Research and Education Center (HREC), and Borderview Research Farm, we do not report any data analysis for those farms. We are potentially adding two new sites this upcoming season at farms with a history of wireworm pressure.
Cover crop treatments (oat/rye) at the ICF (Burlington) and the West Haven sites exhibited opposing results. Sweet potatoes from oat cover crop treatments at ICF (i.e. control) displayed significantly fewer wireworm galleries when compared with rye cover crop treatments (see figure below). At the West Haven site, oat cover crop treatments displayed a mean of 4.75 galleries/sweet potato, with zero incidence of wireworm damage in rye cover crop treatments (graph not shown).
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.
Due to the low levels of wireworm pressure at the UVM Horticultural Research and Education Center (HREC), and Borderview Research Farm, we do not report any data analysis for those farms.
At the Burlington site (ICF), biorational soil drenches failed to reduce wireworm damage, when compared to untreated control. Several treatments increased wireworm pressure and exhibited significant increases in wireworm galleries (see figure below). The grain controls (sterilized barley and millet) also significantly increased the incidence of wireworm damage when compared to the untreated control.
Wireworm soil drench treatments for Intervale Community Farm Trials (2021)
Key Conclusions and Recommendations from the Research Results:
- The application of Metarhizium anisopliae and other biorational soil drenches did not effectively reduce wireworm damage in sweet potatoes in some cases and even increased wireworm pressure in others. Farmers should be cautious when considering the use of these specific treatments until their efficacy is further evaluated.
- Biorational soil drenches, including entomopathogenic fungi, did not affect wireworm pressure in the 2021 field season. Farmers may need to exercise caution when considering the use of biorational soil drenches for wireworm control until further research provides more conclusive evidence of their efficacy.
- Rye cover crop treatments exhibited reduced wireworm pressure in sweet potatoes compared to oat cover crops in the 2022 field season. This trend was consistent at commercial farm sites. Farmers should consider using rye cover crops to mitigate wireworm damage in sweet potato plantings.
- Biopesticide trials with entomopathogenic fungi were inconclusive due to an absence of wireworm pressure at the research farms in the 2022 field season. Further research and testing may be needed to assess the effectiveness of biopesticides for wireworm management.
- High glucosinolate mustard (HGM) biofumigation showed significant reduction in wireworm pressure in sweet potatoes compared to no cover crop control. Farmers are recommended to consider implementing HGM biofumigation to manage wireworm infestations in sweet potato plantings.
Overall, the research suggests that implementing high glucosinolate mustard biofumigation and rye cover crop treatments can be beneficial for managing wireworm pressure in sweet potato plantings. Farmers should consider these strategies as potential tactics for reducing wireworm damage and protecting their crop yields.
These conclusions and recommendations provide valuable insights for farmers making decisions about adopting specific practices or strategies to manage wireworm infestations in sweet potato plantings.
Education
48 growers and 6 agricultural service providers across Vermont, New Hampshire, Maine, Massachusetts, Connecticut, Rhode Island, and New York were enrolled in our education program. Our educational curriculum focused 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 the curriculum was divided into two general categories: knowledge building and skill development.
Knowledge Building: Growers participating in our educational program received detailed and practical knowledge on a variety of relevant topics. These topics included: 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 were trained in the proper deployment of various low-impact and ecologically based IPM tactics for wireworm management. Though comprehensive in nature, these trainings paid particular attention to cultural and biological control tactics including those tested in our field trials. Farm demonstrations and field days at the UVM Horticultural Research and Education Center provided 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.
Milestones
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;
150
8
48
6
May 13, 2022
Completed
July 01, 2022
During the 2020 season, 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. We received contacts for 38 growers volunteering to be a part of our program.
We garnered new interest from farmers within the region to participate in our educational program following the 2021 season, adding ten more contacts.
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.
50
2
48
6
April 30, 2021
Completed
July 01, 2022
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.
43
2
20
3
September 01, 2023
Completed
We hosted two field days at HREC in 2022 and 2023 with roughly 10 growers at each.
We presented our research at the 2022 Entomology society of America Conference
20
6
10
3
September 01, 2023
Completed
Growers and extension professionals were informed on our research trials from the previous 2 years.
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.
6
2
4
September 30, 2023
Completed
We supported four farmers with implementing either HGM or rye cover crop as a deterrent for wireworm in their sweet potatoes. We also provided info on the biology, the amount of pest pressure and potential of complication of using entomopathogenic nematodes.
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.
50
3
150
December 30, 2022
Completed
For both the 2021 and 2022 growing seasons our research team initiated a weekly pest and scouting newsletter in collaboration with the Vermont Vegetable and Berry Growers Association. As part of these scouting reports, we included weekly information regarding an array of relevant pests particularly pests that we work directly with in our funded projects. Basic wireworm biology, ecology and recommended best practices were added to the report throughout the entire season.
We also disseminated our research brief including all of our results from the 2021 season in February 2022.
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).
250
50
264
February 28, 2023
Completed
- We presented our research findings and basic wireworm information at to the 144 farmers attending the virtual 2021 Vermont Vegetable and Berry Growers Association's Conference.
- We presented our research at the 2021 New England Vegetable & Fruit Conference
- In addition we presented our work on this project at the NofaVT 2023 Winter Conference.
- We presented our research updates and wireworm ecology knowledge in a VVBGA online webinar in winter 2022.
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.
150
10
12
March 30, 2023
Completed
We sent our verification surveys to the entire list in our educational program. Unfortunately, despite several attempts, we received a very low response of roughly 12 growers. These growers all indicated that the information and research results provided important information and knowledge to better manage wireworms.
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
10
6
August 26, 2023
Completed
Six growers indicated that they plan to utilize the practices directly on their farms. We provided direct consultations for Bear Roots Farm, Intervale Community Farm, Otter Point Farm, Cedar Circle Farm, Last Resort Farm, and Burnt Rock Farm.
Milestone Activities and Participation Summary
Educational activities:
Participation Summary:
Learning Outcomes
Knowledge of wireworm ecology, biology, and management were indicated as the primary benefits derived from our educational program. Some growers also referenced a better understanding of entomopathogenic fungi and HGM as tactics for pest management. Finally, consistently growers underscored their appreciation for the component ways that biological controls can suppress wireworms as part of a larger IPM program.
We collected our primary verification data via an online survey distributed directly to the farmers participating in our educational program. It is our belief from conversations with some of the growers in the program that survey fatigue is likely the primary factor for the low response rate.
Performance Target Outcomes
Target #1
75
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.
Application of this knowledge will occur on up to 50 acres of sweet potato cropland
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.
6
These farmers either changed their cover crop or looked to use a biological control application to suppress wireworm damage.
3 acres of sweet potatoes
We were unable to directly measure the benefits to production resulting from the change or adoption of the tested practices.
Our verification survey, distributed at the end of the project, was the primary direct indicator for our evaluation. Unfortunately, only 12 farmers responded to the survey despite our large distribution to both our educational program farmers and the entire Vermont Vegetable and Berry Growers Association (VVBGA) listserv. Of the farmers that submitted direct responses in our surveys or informally contacted us, many indicated that they are consistently inundated with surveys and have some level of survey fatigue. This seems to be a growing trend for many of our projects. It seems that our PAR meetings were the best way to capture grower sentiment and feedback. However, in the PAR environment, much of the feedback and discussions are largely informal in the sense that we are not able to tally up or record feedback in the moment, as it can disrupt the normal flow of communication and create an uncomfortable environment.
The primary verified outcome from the project centered upon the use of cover crops and the type of cover crops being used. Several growers indicated through our direct conversations during our PAR meetings (~7-9 farmers per season) and other farm consultations (~3-4 farmers per season) that they were now aware of the benefits of rye cover crops (in comparison to oat) when planting sweet potatoes or other root crops sensitive to wireworm pressure. However, several also mentioned that they might avoid grass-based cover crops altogether when planting a root crop the next season. This was a direct result of our educational program, whereby we underscored the risks of grass-based cover crops for recruiting click beetle females. One farmer that has been growing sweet potatoes and Andean potatoes for over a decade within the region expressed validation for their rotational sequencing where they have avoided grass cover crops.
Furthermore, it was difficult to assess direct measurements of "recovered" losses from farmers. Because many of our farmers are organic growers and are consistently using a suite of tactics to manage pests, it is very difficult to directly assess the benefits of a single tactic. This is a stark contrast from evaluating conventional or industrial methods where single chemical applications are easily isolated from other tactics.
Our team is very curious how other SARE researchers are best verifying the outcomes of their educational programs and research trials. There is no doubt from my interactions with growers that our programs and research is valuable and has supported the grower community. The issue has been developing easy ways to document those outcomes without alienating growers. I think a workshop from SARE on best practices for verification or brainstorming ways to combine efforts among different projects in a single verification survey or the like, could be very valuable. It is frustrating to spend so much time doing research and supporting growers with these projects but remain limited in our capacity to document or verify the tangible outcomes.
Additional Project Outcomes
The project built upon our teams already growing expertise in biological control applications for organic vegetable growers. In addition, the project has provided a fertile ground for educating undergraduate students interested in Extension and entomology. Since the start of the project we have trained 12 different undergraduates in the use of biological control for insect pest management.
One of the key challenges for this project seemed to be the variability in the wireworm populations through fields and locations. The first two years, a couple of trials were uninformative due to a lack of wireworm pressure. This often led to inconclusive results or reduced the statistical power of our experimental designs. That challenge, however, led to an opportunity where we developed a wireworm monitoring protocol modified from other research studies. The new protocol also supported our current novel approaches project as it was the impetus behind our burgeoning lab-reared wireworm colony. This colony has helped us to optimize the dosage for our biological control applications in those field trials.