Development and delivery of post-harvest spotted wing Drosophila cultural control tactics for for NCR tart cherry growers

Progress report for LNC20-435

Project Type: Research and Education
Funds awarded in 2020: $208,507.00
Projected End Date: 11/30/2023
Grant Recipient: Michigan State University
Region: North Central
State: Michigan
Project Coordinator:
Dr. Matthew Grieshop
Michigan State University
Co-Coordinators:
Marianna Szucs
Michigan State University
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Project Information

Summary:

Our research project will develop and deliver cultural post-harvest management tactics for fruit wastes utilized by the invasive pest, spotted wing Drosophila (Drosophila suzukii) (SWD). SWD is the number one insect pest of cherries in the NCR and is currently managed with repeated application of broad-spectrum insecticides. The waste fruit disposal methods developed will include composting and fruit crushing. Preliminary research conducted by our team demonstrates that SWD readily reproduces on waste fruits and that composting fruit wastes with animal manures, introduction of black soldier fly and/or crushing fruit wastes reduce SWD emergence by up to 100%. Project activities will evaluate these tactics at field scale, evaluate the potential of soluble nitrogen in place of animal manures, evaluate the feasibility of using BSF to compost field wastes, demonstrate the tactics to regional fruit growers and develop extension products highlighting these cultural control tactics. Our project meets all three desired outcomes for NCSARE research and education projects. Developing alternatives to costly insecticide applications and integrating cultural/sanitation pest management methods for SWD will improve farmer profitability, by reducing production costs and crop losses. Reduced reliance on broad spectrum insecticides will improve the environmental quality and natural resource base within cherry production systems by conserving biodiversity. Reduced reliance on broad spectrum insecticides and improved profitability will enhance the quality of life for farmers, farm workers and society at large by reducing insecticide exposure as well as by preventing the loss of historically important tart cherry orchards from NW Michigan.

Project Objectives:

1): Determine feasibility of fruit crushing/cultivation/composting as cultural control for SWD on fruit wastes.

2): Determine the impact of soluble nitrogen fertilizers and black soldier fly on SWD reproduction in fruit wastes.

3): Develop and demonstrate optimized practices utilizing combined tactics for managing SWD populations in fruit wastes.

4): Deliver optimized practices to grower clientele

Learning Outcome: Improved understanding of how post-harvest waste management impacts SWD populations and methodology for waste disposal using in field crushing or composting.

Action Outcome: Growers will adopt post-harvest management strategies to reduce local SWD populations, reducing the need for broad spectrum pesticide applications.

Introduction:

Michigan tart cherry growers are the immediate stakeholders served by our project team. However, the project will be applicable to soft fruit producers across the NCR and USA. The project team has a well-developed relationship with the fruit industry in MI and regional commodity groups funded  the development of our preliminary data. While our research has strong regional support, it directly addresses the management of SWD, an insect that is an identified stakeholder priority of the North Eastern, Southern, North Central and Western IPM centers as outlined in numerous pest management strategic plans. Furthermore, all major fruit commodities that have published Pest Management Strategic Plans (PMSP) (sweet and tart cherries, blueberries, raspberries, strawberries and grapes) report the development of new pest management tactics to replace outgoing insecticides as an important priority.

Our proposal will develop cultural management tactics for Spotted wing Drosophila (Drosophila suzukii) (SWD)  that can be integrated into existing IPM programs. We will provide farm scale proof of concept for these sanitation techniques as well as evaluate novel sanitation techniques. Michigan is the leading producer of tart cherries with 32,500 acres, and SWD has rapidly become the biggest economic challenge faced by this important NCR crop. Post-harvest management of fruit wastes is important because tart cherry growers are routinely required to set aside up to 40% of fruit due to marketing orders and fruit that is set aside serves as an important resource for SWD development. Post-harvest management will reduce local SWD populations within a growing season and the number of SWD entering the overwintering period. Ultimately, this will reduce applications of broad-spectrum insecticides to fruit just prior to harvest. Incorporating sanitation based cultural controls into SWD management programs will help growers meet Maximum Residue Limits (MRLs) and minimize negative impacts on beneficial organisms —i.e. bees, pollinators and natural enemies of key pests.

Our project will complement previous SARE projects in two areas: 1) sustainable control of SWD (15 funded projects) and 2) exploration of black soldier fly (BSF) as an on-farm waste management tool (7 funded projects). SARE funded SWD projects have ranged from evaluating protective culture, attract and kill, mass trapping and botanical insecticides. SARE funded work on BSF has focused on their use as animal feeds and composting farm wastes. Our project will complement these studies by providing farm scale proof of concept data on cultural sanitation approaches to post harvest management of SWD and explore the use of BSF larvae as interference biocontrol.

Need/Problem: Since 2008, SWD has become a global pest of berries and stone fruits and is found throughout the USA with annual damage and control costs in the HUNDREDS of millions of dollars (Bolda et al. 2010). The keys to this pest’s rapid rise to critical importance lie in its unique ovipositor, allowing it to insert eggs into fruit, rapid generation time (as short as 8 days) and broad host range (Lee et al. 2011). Perennial fruit crops threatened by SWD are important to the US economy, with a market value of $11.7 billion, plus they provide important nutrients and are valuable components of local food systems. In Michigan, the Tart Cherry and Blueberry industries have an annual farm gate value of $40 Million and $116 Million, respectively (USDA NASS 2017). Invasive pests notwithstanding, pest management is consistently listed as a prime concern for fruit growers, and insecticides alone can account for as much as 13% of yearly production expenses (Perez & Ali, 2009). Insect pest management in United States fruit production systems has faced unprecedented challenges in the last decade. These challenges include: the loss of insecticides through revised EPA regulations (http://www.epa.gov/opp00001/reregistration/azm/), rapid development of pest resistance to key insecticides (Gress and Zalom, 2018), increasing public concerns about negative impacts associated with insecticides (Damalas & Eleftherohorinos, 2011), and the promulgation of international MRLs (http://www.fas.usda.gov/maximum-residue-limits-mrl-database).

 

Post harvest management provides an opportunity for cultural control: The establishment of sustainable IPM programs for SWD demands that we develop non-pesticide based management tactics. Currently, the most successful non-pesticidal based management tactic has been protecting small fruit crops with insect mesh. While exclusion netting can provide significant reductions in SWD damage it is expensive (~$30,000 per acre) and not easily adapted to existing plantings (Leach et al. 2016; Rogers et al. 2016). Bal et al. (2017) demonstrated that SWD readily reproduces in unharvested fruit and fruit processing remnants, but little attention has been paid to post harvest management. Removal of fruit resources and sanitation can reduce SWD local populations. For example, Leach et al (2018) demonstrated that increased harvest frequency and removal of dropped or waste fruit reduces populations by up to 60%. Burial of wastes has also been evaluated but research suggests that shallow burial is not effective at farm scales with depths of at least 24 cm (10 inches) needed to achieve 95% emergence reductions (Hooper and Grieshop, 2020). 

Preliminary Data: The project team has previously demonstrated that crushing and composting of fruit wastes significantly reduces SWD reproduction under laboratory and semi-field conditions. A series of 2016 experiments conducted by Dr. Rothwell and Ms. Pochubay evaluated mechanical, in-field crushing of post-harvest tart cherries, demonstrating reduced duration and overall level of SWD reproduction. Likewise, experiments conducted in Dr. Grieshop’s program have shown that composting apple pomace (apple cider leftovers) with relatively small volumes (<25%) of poultry manure can reduce SWD utilization of this common fruit waste by over 95%.

Fruit crushing was evaluated in 2016 by collecting ripe, unsprayed, Montmorency tart cherries into small windrows in the center of the sod row middles. A golf cart was used to smash windrows by driving over them twice and samples of smashed and intact cherries were collected 1, 3, 5, 7 and nine days afterwards  and exposed to adult SWD in the lab. Crushing fruit in the orchard reduced the number of SWD larvae at all timings, with 100% reductions recorded for fruit by day 7 and 9.

KNOWLEDGE GAP 1: While preliminary data demonstrates that crushing fruit reduces SWD reproduction, this tactic has not been evaluated at a scale relevant to farming operations nor have we evaluated whether crushing reduces local populations of wild flies. We will address this Gap in objective 1.

Composting fruit wastes with animal manures has also shown promising results in laboratory and field experiments. A laboratory experiment evaluated five mixtures of organic apple pomace (cider leftovers) with organic poultry chicken manure (100, 99, 95, 90, and 80% pomace). Poultry manure significantly affected SWD reproduction with 19.2%, 34.3%, and 81.8% reductions in the 95%, 90% and 80% apple pomace treatments, respectively  (Hooper and Grieshop 2019). A field experiment with similar pomace/manure mixtures  (100%, 90%, 75%, 50%, and 0% pomace) in 100 liter, caged experimental arenas had similar results. There was a significant effect for the quantity of apple pomace on SWD reproduction with emergence decreasing by 76.3%, 95.0%, 95.9%, and 99.4% for treatments containing 90%, 75%, 50%, and 0% apple pomace, respectively. These results further support the hypothesis that adding poultry manure to fruit wastes significantly reduces the reproductive quality of these wastes.

KNOWLEDGE GAP 2: Composting waste fruit with poultry manure reduces both laboratory and field SWD reproduction at small scales. This tactic has not been evaluated at the farm scale nor have we evaluated the impact of composting fruit wastes on local SWD populations. We will address this Gap in objective 1.

Chicken manure is high in nitrogen, and high nitrogen substrates decrease oviposition and egg viability of SWD and D. melanogaster (Joshi et al., 1997; Belloni et al., 2018). Belloni et al. (2018) determined that high concentrations of dietary urea and ammonia reduced SWD oviposition by 70% and 60%, respectively.  If nitrogen content is the causal mechanism behind the observed reductions in reproduction then growers could potentially use nitrate or ammonia based fertilizers in place of chicken manure. 

KNOWLEDGE GAP 3: Nitrogen content may explain how the addition of manure reduces SWD reproduction. Soluble nitrogen sources are cheaper and easier to handle compared to manures and could be used to manage fruit wastes on planting floors or in canopies. Thus, determining the form and levels of N needed to reduce SWD reproduction in fruit wastes is the 1st step in developing this tactic. We will address this Gap in objective 2.

Black soldier flies (Hermetia illucens) (Diptera: Stratiomyidae) (BSF) are a non-pestilent insect used for biological control of stable and house flies in manure management systems (Sheppard, 1983, Miranda et al. 2019). We have conducted lab experiments evaluating the impact of BSF composting of fruit wastes on SWD reproduction. 200  ml of apple pomace was exposed to SWD adults for 48 hours and BSF larvae added at day 0 (at the same time as SWD), 3 (1 day after SWD) and 7 (5 days after SWD) or not at all (control) after which SWD offspring were collected on a daily basis. The addition of BSF at day 0 completely eliminated SWD reproduction and provided a 10-fold and 3-fold reduction when BSF were added to wastes on day 3 and 7, respectively. BSF can be readily purchased from a variety of sources and may provide another attractive alternative for managing SWD  populations in fruit wastes.

KNOWLEDGE GAP 4: How can BSF be best leveraged as a post-harvest control strategy for SWD and other insect pests that utilize fruit wastes? The first step of this process is to understand the biological mechanisms behind observed reductions. The next step is to develop a “dose-response” curve and the final step is to evaluate and demonstrate this tactic at field scale. We will address this Gap in objectives 2 and 3.

Integration of pest management tactics and strategies is a core IPM principle and one that is desperately needed for the development of sustainable SWD management programs (Lee et al., 2011.; Sial et al. 2018). While the development of a fully integrated program is outside the scope of this project, the development of optimal integrated waste management strategies will provide a vital step forward to this ultimate goal.  Furthermore, our grower collaborators have identified management of sap beetles (Coleoptera: Nitidulidae) as an additional post harvest concern. 

KNOWLEDGE GAP 5: The effects and practicality of integrating multiple post-harvest fruit waste management tactics for reducing SWD and other pest insect reproduction are unknown. The combination of fruit crushing with either manure or soluble nitrogen applications may provide synergistic reductions in fly populations but the potential costs/benefits associated with integration of these processes is unknown. We will address this Gap in objective 3.

Cooperators

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Research

Hypothesis:

1) Crushing and manure applications will reduce SWD reproduction in waste cherries

2) Nitrogen fertilizers will reduce SWD reproduction in waste cherries

3) Black soldier fly will reduce SWD reproduction in waste cherries.

Materials and methods:

Approach and Methods: Activities for objectives 1 and 3 will involve extensive on farm, grower collaborative work. Objective 2 will involve largely laboratory proof of concept experiments used to inform objective 3. We will meet regularly throughout the project with our collaborating growers to provide updates and to co-create field methodology and extension outputs. A project timetable is presented in figure 7.

 

Objective 1. Evaluate and compare farm-scale feasibility of fruit crushing/cultivation and composting as cultural control tactics for reducing SWD and other drosophilid populations on aggregated post-harvest tart cherry wastes: Our farmer collaborators have expressed a need for “field scale” data on crushing and composting of fruit wastes before they will adopt these practices and have suggested that we monitor additional problem insects that build on waste cherries such as sap beetles. To address these needs we will evaluate the two tactics on waste tart cherries at the MSU Northwest Michigan Horticultural Research Center (NWMHRC) and three collaborating farm/fruit processing locations in years 1 and 2. Shoreline Fruit Growers, Garthe Farms, Cherry Bay Orchards, and Smeltzer Orchard Company will provide field locations, waste cherries and farm labor/equipment to establish experiments. The project team is requesting $30,000 over the course of the project to offset costs to our grower collaborators. 

Experiment 1.1 We will demonstrate and evaluate fruit crushing and composting at farm scale at our four field sites. The experiment will consist of four treatments; an untreated control, 15% and 30% poultry manure composting treatments (by volume) and mechanical crushing of fruit with a tractor mounted roller or flail mower with four replicates per site. Experimental units will consist of 100-300 liter (0.1-0.3 cubic meter) quantities of waste cherries. Fruit wastes will be mixed with poultry manure with a front loader or similar tractor-based implement. SWD and other insect development will be monitored using a combination of emergence cages, laboratory assessment of emergence from sub-samples, and a trapping grid. Waste piles will be separated by at least 20 m and placed in an open field adjacent to fruit production or processing sites. 

We will begin experiments in late July or early August and terminate them after 10 weeks. Adult SWD and other insect emergence will be monitored using emergence cages and weekly fruit samples. A 60 cm x 60 cm x 60 cm mesh emergence cage (Fig. 8) will be placed on the center of each waste pile and adult fruit flies and other insects collected on a weekly basis. Five, 200 ml fruit samples will be collected from each pile and adult fruit flies reared out in laboratory emergence arenas and checked daily for 5 weeks or until no emergence is detected for 7 days.  To assess impacts on SWD density within the treated area, three 946 ml deli cup SWD traps baited with a commercial lure will be situated around each pile with one trap directly over fruit wastes and two traps placed within 5 m of each waste pile. We will record the number of male and female SWD, number of Drosophila melanogaster and other drosophilids and sap beetles at the family level. Data will be analyzed with repeated measures MANOVA with treatment as a fixed factor and block and time as random factors.

Objective 2.  Determine the impact of soluble nitrogen fertilizers and black soldier fly on SWD reproduction in fruit wastes.: When presented with preliminary data on management of SWD on post harvest wastes our grower collaborators requested that we evaluate soluble fertilizers as these products are less expensive, more readily available and require less machinery for handling. Our grower collaborators also expressed interest in evaluation of BSF composting. However, before these approaches are ready for field testing, proof of concept work needs to be conducted. 

Experiment 2.1 will determine the effect of soluble synthetic nitrogen on SWD reproduction on waste cherries and Experiment 2.2 will determine if soluble nitrogen on fresh tart cherries will reduce SWD oviposition. Experiment 2.3 will determine the optimal “dose” of black soldier fly (BSF) to use per liter of waste cherries to minimize SWD emergence. Waste cherries will be collected and stored in a walk in freezer located on the MSU campus. Fresh cherries will be purchased as needed from local produce suppliers. Laboratory trials will be conducted in growth chambers located at the MSU insectary and Department of Entomology during the fall, winter and spring months.

Experiment 2.1: In fall 2021 we will evaluate five rates of urea, ammonium, nitrate and calcium nitrate, an untreated control and a positive control containing 20% (by volume) organic chicken manure treatments with at least ten replicates. Nitrogen treatments will be assigned based on the estimated percentage nitrogen and density of chicken manure at 25% moisture –5.415% and 1.08 g/ml, respectively. We will evaluate the three fertilizers based on the mass of Nitrogen estimated to be contained in 10%, 25%, 50%, 100%, and 150% chicken manure/fruit blends. For example, for a 46% Urea fertilizer the resulting mass of fertilizer added to 200 ml of fruit waste would be: 1.18 g, 2.95 g, 5.9 g, 11.8 g, and 17.7 g, respectively. Experiments will use emergence arenas described in Experiment 1.1 (Fig. 9). Ten, 7 d old female adult SWD will be placed in each arena and allowed to oviposit for 48 h after which they will be removed with an aspirator. Arenas will be held in a growth chamber (25˚C, 70% RH, 16:8 L:D), and checked daily for emergence and flies counted and removed for five weeks or after 7 days without emergence.  Data will be analyzed utilizing a repeated measures ANOVA with nitrogen source (fertilizer) and rate as fixed factors and experimental run and collection date as random factors.

Experiment 2.2: We will determine the impact of soluble nitrogen applications to fresh cherries on SWD oviposition and development. We will evaluate at least five fertilizer types/rates (identified in Experiment 2.1)  tested in choice bioassays. The bioassays will be conducted in a 25 cm (H) x 25 cm (D) x 75 cm (W) arena containing untreated and treated fruit. Fertilizers will be applied by dipping five cherries into solution. The five treated fruits and a second set of water dipped fruit (control) will be placed at opposite ends of the arena and 10 7 d old, mated female SWD released into the arenas. Flies will be allowed to interact with fruit for 24 hours and presence on fruit recorded throughout the experiment. Fruits will be collected, oviposition scars counted using a stereomicroscope and offspring from the fruits reared out and counted. Fly count data will be analyzed utilizing a repeated measures ANOVA with nitrogen source (fertilizer rate) and rate (% chicken manure equivalent) treatment as fixed factors and experimental run and observation time as random factors. Oviposition scar and offspring data will be analyzed utilizing an ANOVA with nitrogen source (fertilizer) and rate treatment as fixed factors.

Experiment 2.3: We will determine an optimal dose of BSF larvae (g of larvae/l of waste) for disrupting SWD reproduction in waste cherries. Laboratory experiments will be conducted in arenas containing 2 l of cherry waste with 5 rates of BSF evaluated (0.1, 0.3, 1, 3 and 10 g per l of waste) and an untreated control and replicated 5 times. Arenas will consist of aluminum baking pans placed within a mesh cage. Wastes will be infested with SWD by introducing 100 SWD mated females to the arenas 48 hours in advance of introducing BSF as 3rd instar maggots. Arenas will be sampled and data analyzed as outlined in Experiment 2.1. This experiment will be carried out between September 2021 and April 2022 and used to inform Experiment 3.3. 

Objective 3. Develop and demonstrate optimized practices utilizing combined crushing, manure and/or nutrient inputs for managing SWD populations in post-harvest fruit wastes in field or orchard plantings: The ultimate goal of our project is to provide NCR tart cherry growers with an integrated set of tactics for post harvest management to reduce SWD use of these resources. In the final field season of the project we will address this in a series of three on farm experiments conducted with grower collaborators at the NWMHRC and 3 grower locations. 

Experiment 3.1: We will evaluate combinations of crushing, composting and soluble nitrogen applications on SWD, sap beetle and other insect development at our 4 field sites. Waste fruit piles will be established as described in Experiment 1.1 and treatments replicated at least four times per site. We will evaluate at least 5 treatments consisting of crushing fruit with a turf roller or flail mower, mixing fruit with manure at the optimal rate identified in Experiment 2.1, mixing fruit with the optimal rate of the best soluble nitrogen fertilizer as identified in Experiment 2.1, a combination treatment of crushing and manure, and a combination treatment of crushing and soluble nitrogen application. Data will be collected and analyzed as described in Experiment 1.1. 

Experiment 3.2: We will determine the impact of soluble nitrogen applications to the canopy and floor of tart cherry orchards on SWD reproduction, in an experiment consisting of five treatments replicated four times in a randomized complete block design at our four field sites. Treatments will consist of an untreated control and three application rates of a single soluble nitrogen source that will be determined based on Experiment 2.2. Nitrogen will be applied utilizing an optimized radial air blast sprayer using a spray volume of 468 l/ha (50 gallons per acre) to 1/10 ha experimental blocks once per week over a four week period. Data will be collected utilizing three yeast-sugar baited 946 ml deli cup traps per experimental plot and fruit samples (see Experiment 1.1) . Three 200 ml samples per plot will be collected from the canopy and floor for five weeks or until fruit is no longer available. Samples will be reared out in growth chambers using deli cup arenas described in objective 1.1 (Fig. 10). Data will be analyzed utilizing a repeated measures MANOVA for each location with treatment as a fixed factor and block and time as random factors. 

Experiment 3.3: We will evaluate the impact of BSF on SWD and other insect development in waste cherry piles at our four field sites. This experiment will consist of three to four treatments based on the outcomes of Experiment 2.3 and be carried out at the NWMHRC and at 3 grower locations. Waste fruit piles will be established as described in Experiment 1.1 and treatments replicated at least four times per site/fruit. 3rd Instar BSF will be placed within the piles at 2-3 rates plus an untreated control. SWD and pest insect data will be collected and analyzed as described in Experiment 1.1. 

Objective 4. Extend project information to growers and pest management industry: Outreach and extension will be conducted throughout the project through: biannual meetings with our grower collaborators, the development of bulletins and publications, delivery of materials at regional grower meetings and at project specific field days and webinars. Activities for this objective are documented in the “Outreach” section. 

Pitfalls : Our research has two expected pitfalls: crop availability and interdependence between our lab work and field work. The first issue faces all research in fruit crops in the NCR region, because of perennial crop vulnerability to climate change induced crop failures. If we experience regional crop failures, we will seek out alternative fruit and vegetable wastes to work with. The second issue applies to Experiments 2.1-2.3. If laboratory work does not provide satisfactory results, we will work with our growers to develop replacement field trials/demonstrations on the proven management techniques of crushing and composting.

Research results and discussion:

We are processing data and running experiments. Will update when completed.

Participation Summary
2 Farmers participating in research

Education

Educational approach:

We have developed a handout and presented research at a field day at the North West Michigan Horticultural Research Center and at the Great Lakes Fruit and Vegetable Expo. We will continue to undertake these activities through the life of the project.

Project Activities

Field Experiment
Laboratory evaluations of nitrogen fertilizers

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

This presentation on project preliminary results was presented at the 2020 Great Lakes Fruit and Vegetable EXPO in Grand Rapids MI on December 9, 2020. PDF Slideshow

Learning Outcomes

5 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
3 Agricultural service providers reported changes in knowledge, skills, and/or attitudes as a result of their participation
Key areas taught:
  • Cultural sanitation techniques for reducing spotted wing Drosophila in post harvest tart cherries

Project Outcomes

Key practices changed:
  • Crushing fruit wastes to eliminate spotted-wing drosophila

  • Composting fruit waste with poultry manure to eliminate spotted-wing drosophila

2 New working collaborations

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.