Using a novel banker plant system to prevent spider mite outbreaks in tomatoes grown in protected culture

View the project final report

Commodities

• Vegetables: tomatoes

Practices

• Pest Management: biological control

Tomatoes are a major cash crop for many small farmers, and early tomatoes command high prices at farm stands and markets. Greenhouse and high tunnels are being used increasingly to produce high-dollar fresh tomatoes. Two-spotted spider mites (TSSM) are a key pest of tomatoes, and are especially damaging in protected culture. TSSM are difficult to detect in tomatoes, often establishing large populations before being noticed. Spraying TSSM outbreaks disrupts beneficial insects and pollinators, poses health risks to applicators and are often ineffective as complete coverage is near impossible. To that end, we propose using a banker plant system—corn infested with non-pest mites, Banks’ Grass Mite (BGM)—to support early establishment of TSSM predators, which will suppress TSSM later in the season. Four farms in three states will participate, each farm possessing a treatment and control house. After planting banker plants in treated structures we will release Feltiella acarisuga, a naturally-occurring TSSM predator, and document their reproduction on banker plants biweekly. To assess TSSM populations in the structure, we will use indicator plants for weekly observations of TSSM numbers as well as presence of Feltiella.

TSSM on tomatoes will be observed subjectively biweekly. Costs associated with TSSM control will be calculated and compared between treated and control houses. Outreach will consist heavily of informal communications with growers, as IPM Labs, Cornell Cooperative Extension and collaborating growers are well tied into the Northeastern farming community. To supplement this, we will print pamphlets to circulate and make several presentations in four states.

Proposed Solution

Will a banker plant system, a non-crop plant hosting a non-pest prey species to support reproduction of natural enemies, prevent mite outbreaks and reduce the cost of pest control and crop failures? By introducing a spider mite that is not a pest of tomatoes, we hope to supply prey to support early introductions of predators, thereby preventing later-season TSSM outbreaks.

Banks’ grass mites (Oligonychus pratensis, BGM) will grow on corn, millet or barley, but cannot reproduce on broadleaved plants. With a stable prey population, we hope to see season-long mite prevention with only a few releases of predators.

An important, naturally occurring predator of spider mites, the predatory gall midge Feltiella acarisuga,, can find isolated pockets of spider mites, control them and reproduce in a variety of crops. However, it is most effective at preventing outbreaks when TSSM populations are low—typically before TSSM damage becomes evident in tomatoes.

The objective of the project is to demonstrate long-term establishment of predatory midges using a banker plant system and concomitant pest suppression. We also hope to demonstrate an overall reduction of costs (including materials, equipment costs, and labor in applying controls and scouting) by comparing treated houses to untreated houses.

Project Methods

Set Up

The project is designed to be implemented successfully by growers with minimal training in entomology—hopefully spurring wider adoption of this innovation. The experimental design has the intent of minimizing any alterations to existing tomato cultural practices.

Four sites each possessing two separate test tomato high tunnels (one control, one treatment) in three northeastern states (NY, PA, VT) will perform set up and observations. Set up will entail:

1. Permits secured from USDA APHIS for movement of BGM to test sites (in progress now; some already secured)

2. BGM grown at IPM Laboratories, Inc. (Locke, NY) will be shipped to test sites and released onto corn seedlings sprouted on test sites. Sites will grow sufficient banker plants to have one plant hosting ~10,000 mites every 1,000ft2 of growing space

3. Bush beans sprouted in treated and control hoop houses; one plant per 1000ft2 of growing space

4. Two releases of 100 Feltiella acarisuga released into treated house
5. Tomatoes planted and maintained as during any other year, including pest management Data Collection

Observations will be performed on a weekly or biweekly basis through the growing season, and parameters observed will be the following:

1. Observations of banker plants (biweekly) to include: a: Presence of Banks’ grass mites on banker plants; b: Qualitative assessment of suitability of BGM colony to support further predatory gall midge reproduction; c: Presence of gall midges and life stages observed

2. Observations of bush beans (weekly) to include: a: Severity of TSSM on first fully expanded trifoliate leaf on a 0-3 scale (0: no mites, 1: fewer than 10 mites, 2: 11-50 mites, 3: >50 mites); b: Presence of gall midges and life stages observed

3. Observations of tomatoes (biweekly) to include: a: Severity of TSSM on each cultivar, subjectively assessed on a 0-3 scale (0: no mites present; 1: TSSM present but below damaging levels; 2: TSSM causing some stippling and discoloration; 3: TSSM causing defoliation); Presence of gall midges and life stages observed

4. All TSSM controls beyond those previously mentioned will be collected through the season. including labor, biocontrols, chemicals, PPE and overhead costs for operating spray

Rationale: Banker/Indicator Plant Data

Maintenance of the test site will involve four sets of banker plants being introduced through the growing season. As with other banker plant systems, the predators can eventually overwhelm the prey on the banker plants, and it becomes necessary to refresh that supply. Bush beans will be replaced once in mid-season, to account for their natural growth cycle.

The data collected on the banker plant will help us determine how long the mite colony remains suitable for Feltiella reproduction. As with other banker plant systems, prey may become exhausted from continuous predation. To keep a constant supply of BGM, some plants are introduced into the growing space, while others are held in reserve to allow BGM to build its population before being exposed to the predators. BGM “reserves” will remain at IPM Labs, to lessen the burden on collaborators. Observations on how long the mites remain present on banker plants will help develop standard practices on successful implementation of this system.

With this in mind, we expect to replace the banker plants four times during the course of season. In real world circumstances, the grower would be able to culture their own BGM using similar practices to other banker plant

Beans are very attractive to TSSM, becoming infested and showing damage before tomatoes, and finding TSSM on beans is much easier than on tomatoes. Data collected from the beans will be used to document when the first TSSM arrive in the hoop house (requiring weekly scouting), roughly what numbers they arrive in and whether the Feltiella are finding TSSM throughout the structure. This will give us a rough sense of pest pressure coming in from outside and will be compared to TSSM levels detected in the crop to determine whether Feltiella are suppressing the spread of TSSM.

Rationale: Crop Data

TSSM levels on the crop are the integral finding of the study. If tomatoes in the treated house become more heavily infested and require greater control measures than the untreated house, the project is a failure. However, Feltiella seen in conjunction with TSSM will constitute a success if TSSM levels remain consistently low.

Eradication of pests is never the goal of an IPM program; maintaining pests below damaging thresholds is. Using a subjective scale for severity of infestation is useful as TSSM is difficult to assess on tomatoes and because all growers use their own judgment to assess pest outbreaks anyway. The cultivar data is useful to determine susceptibility of certain varieties to spider mite infestation to inform future cultivar recommendations.

Finally, the cost analysis is used to make a stronger case for adoption of the banker plant system, should it prove successful. Chemical and protective materials costs will be calculated on a per ounce basis at 2015 prices from Griffin Greenhouse Supply, Inc. to keep prices standard between growers. Labor costs will be calculated based on what the farm pays the pesticide or biocontrol applicator. An extra 10% will be added to pesticide and concomitant labor costs to account for spray equipment wear and tear. The data will be compared between control and treated houses and also between farms to assess the real-world costs of TSSM control in tomatoes.

Data Analysis

Data should be relatively clean and easy to comprehend even without much analysis. Seeing as the quantitative variables have been simplified to only four possible outcomes, a simple graph of TSSM on beans and tomatoes over time would synthesize data into a compelling and comprehensible figure that would resonate with the farmers to whom we hope to disseminate the results. If need be, we can look at significant difference between costs accrued between treated and control houses, but with only four replicates, the power of any statistical analysis is limited.

Project Timetable

For purposes of this study, we will use growing weeks to simplify when tasks need to take place, and all tasks will take place in 2016. Growing week 12 starts Sunday, March 20, and week numbers are sequential after that. Jill Rotondo will perform all tasks at Intervale and Nic Ellis will perform all tasks at J-Mar Farm. Long Island farmers will perform weekly observations of beans and maintenance of experimental organisms, Sandy Menasha will perform biweekly observations of banker plants, beans and tomatoes.

Collaborators are expected to spend roughly 1 hour a week performing observations and 10 hours during the course of the study to grow/maintain banker plants. Different farms plant out at different times, but involvement will begin no earlier than March 21, 2016. An IPM Labs entomologist will be travelling to all the key collaborators to show what the study organisms look like and how to find them. Those trips will happen at dates to be determined in April (Riverhead) and May (Intervale).

Week 12: Project begins: a: Farmers plant 1 pot of corn seeds per 1000ft2 of growing space in treated house and hold in protected place; b: Farmers plant 3 bean seeds every 1,000ft2 growing space among crops in both houses

Week 14: a: BGM shipped to farms to be released onto corn seedlings; b: Corn seeds started at Intervale Community Farm

Week 16: a: Banker plants planted out to treatment house; b: First observation of beans and tomatoes; c: BGM shipped to Intervale to release onto corn seedlings

Week 17: beans observed

Week 18: a: Intervale plants tomatoes, beans and banker plants; b: 100 Feltiella shipped and released in treatment houses; c: Second observation of banker plants, beans and tomatoes (first observation at ICF)

Week 19: a: Second introduction of Feltiella into treatment houses; b: Beans observed Week 20: Banker plants, beans and tomatoes observed

Weeks 21-38: beans observed

Every other week from week 22-38: banker plants and tomatoes observed

Week 22, 26 and 30: corn seeds started in protected site

Week 24, 28 and 32: BGM shipped and placed on corn seedlings

Week 26, 30 and 34: new banker plants planted out; exhausted banker plants removed Week 38: last observation

Observations will be reported to IPM Labs by Friday of every week, who will then compile it into an Excel spreadsheet. Data synthesis and analysis will begin on week 39, with creation of PowerPoint presentation and pamphlets to be completed by week 48.

Outreach

IPM Laboratories already communicates directly with hundreds of farmers throughout the country via email, phone and in-person consultations. We will inform any interested parties about the results of the studies as an ongoing process. Furthermore, Carol Glenister is invited to give presentations throughout the Northeast. Sandy Menasha, as part of Cornell Cooperative Extension, will being doing the same.

Carol Glenister will develop a PowerPoint presentation used by Nic Ellis, Jill Rotondo, IPM Labs and Sandy Menasha at meetings detailed below and others. Funding will create 2,000 printed pamphlets outlining the findings. These will be distributed at the meetings detailed below and several others, as well as circulated with trade periodicals. Additional pamphlets will be purchased by IPM Labs, as needed. IPM Labs will distribute articles to various northeastern extension agents and trade publications to circulate findings via email and trade journal articles.

Carol Glenister will speak at New York State Vegetable Growers Association meeting in Syracuse, NY and the Mid- Atlantic Fruit and Vegetable Convention in Hershey, PA. Funding for those engagements is in our budget.

Furthermore, we will ask for speaking time at Cultivate’17, AmericanHort’s annual meeting in Columbus, OH.

Nic Ellis, being already highly engaged with produce growers in Southeastern Pennsylvania, has regular speaking engagements, which he can use to discuss the findings, as well as his informal outreach with existing and potential clients.Jill Rotondo will present the PowerPoint presentation to Northeastern Organic Farming Association winter conference in Burlington, VT.

Sandy Menasha, being in extension in a heavily agricultural area, talks with growers all the time, and will disseminate findings through informal gatherings. She will send out newsletters and alerts through outlets pertaining to extension. The Long Island Agricultural Forum will also provide an opportunity for Sandy to present on our findings.