Progress report for LNE25-500R
Project Information
Project Focus: High tunnel production across the Northeast is increasing to mitigate extreme weather event impacts on vegetable crops. These protected environments also promote the establishment of damaging pests (i.e., aphids, spider mites). Because these pests can overwinter within these structures and increase their populations rapidly before detection, they can cause significant economic damage. Successful management without pesticides using biocontrol requires costly prophylactic releases of commercially-reared natural enemies or attracting those that occur in the wild. This project addresses high tunnel grower needs identified by our regional surveys to provide evidence-based biocontrol guidelines for sustainable vegetable production.
Successful integrated pest management (IPM) combines multiple strategies (i.e., scouting, cultural, biocontrol, etc.). Plant-mediated systems, which use plants in combination with other IPM tactics to reduce pests, are a potential component of IPM. Alyssum is used to attract and sustain natural enemies. Bush beans are a trap and indicator plant for spider mites and thrips. Although both systems are used by some innovative growers, data are lacking about their contribution to reducing pest damage and sustaining natural enemies on crops. Growers need confidence that these systems work and guidelines for their use. The optimal rate of deployment is unknown, but this information is essential for efficacy.
Solution and Approach: The objective of this project is to optimize plant-mediated IPM systems in high tunnel vegetables. Different deployment rates of the systems within tomato and cucumber production will be investigated: (1) bush bean trap plants to detect spider mites and thrips, and (2) Alyssum habitat plants to attract and sustain aphid natural enemies. Our hypothesis is that plant-mediated systems (Alyssum habitat plants and bean trap plants) enhance sustainable IPM in high tunnel tomato and cucumber production. It is assumed that natural enemy establishment increases, and pest suppression improves at higher deployment rates, but how many is best? Results will lead to increased grower adoption of these systems at rates that maximize pest management. By detecting pests and establishing biocontrol populations early, the need for pesticide applications and repeat, costly purchases of natural enemies would be reduced.
Growers will be active research participants. The trials will occur on commercial farms and growers will assist with production and deployment of the systems. They will also receive one-on-one assistance with developing their IPM plans. They will also have opportunities to provide feedback on the deliverables. Guidelines for using these systems in high tunnels to prevent economic crop damage will be produced, presentations at regional workshops/conferences and an on-farm demo will be given and we anticipate a peer reviewed publication to result from this work. Information will be disseminated though our regional network of high tunnel stakeholders, to increase grower adoption across the region.
The objective is to optimize the use of plant-mediated IPM systems in high tunnel vegetable production. Different deployment rates of two systems within tomato and cucumber production will be investigated (1) bush bean trap plants to detect spider mites and thrips and (2) alyssum habitat plants to attract and sustain aphid natural enemies. Results will lead to increased grower adoption of systems and rates that maximize pest management on crops. By detecting pests and establishing biocontrol populations early in the cropping cycle, the need for pesticide applications and repeat, costly purchases of natural enemies would be reduced.
High tunnel production has increased over the past decade. This allows growers to mitigate unpredictable fluctuations in temperature and precipitation and protect high-value crops from extreme, unseasonable weather events(1-3). Vermont farms are small diversified, family-owned operations and specialty crops are critical for their economic survival. According to 2022 Ag Census data, there are 6,537 farms in Vermont and 744 of those (11%) sell vegetables. 30% of the farms are operated by new and beginning producers with 44% of the new wave being comprised on women(4).
High tunnels also provide environmental conditions for pest outbreaks(5-7). Surveys conducted by the PI and other collaborators reflect aphids, thrips, and spider mites, are damaging pests. Over 75% of respondents indicated aphids were most damaging with over 40% rating damage as moderate-severe(8,9). These smaller pests are particularly problematic to manage because they hide deep within the crevices and plant blossoms and go unnoticed by growers until extensive damage occurs.
Organic production is on the rise as consumers demand ‘sustainably’ grown produce without pesticides(10,11). Organic growers have limited cost-effective options for managing pests. Washing pests from infested crops increases labor, repeat applications of biocontrols is expensive and the variety of reduced risk pesticides available are often broad spectrum(12). Not only do these pesticides affect pests, but also natural enemies and pollinators that visit crops(13). Top conservation practices of interest and implemented by Vermont agricultural producers are reducing or eliminating pesticide applications and providing wildlife and pollinator habitat(14).
The adoption of IPM is key to continue the downward trend of pesticide use in agriculture, especially to protect beneficials(13,15). In tunnels, this can be achieved through the use of plant-mediated IPM systems. These systems offer a cost-effective, innovative approach to sustainably manage pests by using plants in combination with other IPM tactics(16,17). There’s a need for the development and refinement of existing IPM strategies, like the incorporation of these systems, and testing new biocontrol agents to combat pests to increase IPM adoption by high tunnel growers. Despite system popularity in ornamentals, use in tunnels is fairly limited, but on the rise. For example, in 2019, 35% of high tunnel growers indicated they used a form of plant-mediated IPM system, a 50% increase from 2016. Use of biocontrols also increased, but with ~50% of growers using them(8). Before investing in biocontrol strategies, growers need the confidence they work and guidelines for their use(8,9).
This project optimizes use of plant-mediated IPM systems (alyssum habitat and bean trap plants) to confirm the strategies are beneficial and feasible in high tunnels and provide guidelines to increase more widespread adoption by growers. It will combine the use of the systems to provide a more comprehensive method to manage pests. This project aligns with the Northeast SARE outcome statement. It recognizes the holistic connection among land, water, air, and all living beings and specifically focuses on a sustainable, cost-effective strategy to manage pests in high tunnel production without the need for pesticides (plant-mediated IPM systems) which promotes an increased quality of on-farm life.
Cooperators
- (Educator and Researcher)
- (Educator and Researcher)
Research
Research sites & design: Eight farms were selected to take part in the research trials. The number of tunnels used for experiments per site ranged from 1-5. The research is being conducted during the summer cropping cycles over three consecutive years (May-September 2025-2027). The most common high tunnel size used for experiments averaged 30x96ft (2,880sqft) each with 5-6 beds for crop production within.
The systems were planted in tunnels in a staggered manner within and between rows. The following treatments were tested based on plant-mediated IPM system deployment rate:
- high rate (20 alyssum habitat plants + 20 bean trap plants tunnel). This equates to 40 systems total; 4 alyssum and 4 bean per bed or ~1 system/72 sqft).
- low rate (10 alyssum habitat plants + 10 bean trap plants tunnel) This equates to 20 systems total; 2 alyssum and 2 bean per bed or ~ 1 system /144 sqft).
- control (no systems)
The systems were tested in two different cropping systems:
- Cucumbers within screened tunnels (3 tunnels x 3 treatments = 9 tunnels total)
- Tomatoes within unscreened tunnels (3 tunnels x 3 treatment = 9 tunnels total)
The rationale for placing both systems in each type of production is that bush bean trap plants for the early detection of spider mites and thrips are suitable in several cropping systems, but may have more value when used in tomatoes because it’s harder to see pest damage on tomato foliage than cucumber foliage. Alyssum may also have value in the screened environments of the cucumber tunnels. Cucumber production in tunnels is challenging due to cucumber beetle damage and screening is often used to exclude them. Natural enemies are excluded due to screening so any that would leave and come back for floral resources would be unable to do so. By providing floral resources with for thrips and spider mite beneficials would enhance their effectiveness by providing a more natural ecosystem within.
Production of plant-mediated IPM systems: Alyssum habitat plants were be grown from seed by the growers at least 4 weeks prior to their crop plantings. We provided the seed and trays and organic potting mix. For the initial planting, bush bean trap plants were also be grown from seed (2 weeks prior to crop transplants) because they grow considerably faster than the alyssum. After the initial planning, bean seeds were sown each scouting date to keep a continuous supply of new growth whereby old bean pants were removed throughout the season. Plantings received drip irrigation and were subjected to standard fertilizers used at each location.
Biocontrol plans: We developed biocontrol plans for each site. The biocontrols were released in the tunnels with the systems established within as both preventatives and when outbreaks occurred. Releases in control tunnels were made by the farmers only when outbreaks were detected. In year we, tomato tunnels received regular releases of Aphidoletes (a predatory fly), Aphidius colemani and ervi (parasitic wasps for aphids), N. fallacis (predatory mite for spider mites prevention) and Micromus (brown lacewings) for when aphid hotspots occurred. In the cucumber tunnels, we used N. cucumeris (predatory mites for thrips), P. persimilis (predatory mite for spider mites), Orius (predatory bug for thrips) and an initial release of N. fallacis predatory mites as a spider mite preventative.
Assessment of natural enemies and pests on the plant-mediated IPM systems: Data was collected every 2-3 weeks throughout the summer growing season (~ 6 total observation dates/year). On each outing, attracted natural enemies (i.e., parasitic wasps and parasitized aphids ‘mummies’, predatory bugs (Orius sp.), syrphid flies, etc.) and pests were counted. We visually inspected each system for 1-minute to observe flying insect activity. We will then shake 3-random sections of the system 10x over a laminated white paper to dislodge small arthropod hiding within. We also placed a yellow sticky card on a stake above the canopy (~5cm above) of a subset of the to trap flying insects for passive sampling and assess in the lab. The same location will be used in each tunnel for the cards (including the control tunnel where no habitat plants will be established). The condition of the planting will be assessed using a rating system (1) healthy (0% damage) - (5) severe decline/death (~76-100% damaged). The system size was measured because attraction may be related to size.
Assessment of pests and natural enemies on crop plants: Crop plants were inspected in the same manner as the IPM systems for pests/natural enemies and occurred at the same time intervals in each tunnel. 16 plants/bed were be inspected at random each outing with the exception of a subset that were inspected adjacent to the habitat or trap plant. We wanted to ensure a comparison of insects in the vicinity of the systems vs. plant that were not. Within each plant, sampling occurred at three levels (low, medium, high) and consisted of 3 leaves per level. The pest damage for each plant was also assessed using the above rating system.
Year 1 Preliminary Results:
This past summer was the first field season and we collected a large amount of data at the farms to help answer our primary research questions. Some preliminary findings are as follows:
Natural enemies observed on alyssum habitat plants: There was a total of 512 natural enemies counted on alyssum habitat plantings in the screened cucumber tunnel and 367 in the unscreened tomato tunnels. In the cucumber tunnels, alyssum provided resources to predatory mites (60% of observed natural enemies). We also saw wild Anystis ( crazee mites) on several occasions. Syrphid flies (15%), parasitic wasps (11%) the predatory bug Orius (5%), spiders (5%), predatory thrips (3%), lady beetles (1%) and others (1%). In the tomato tunnels, alyssum provided resources primarily to wild syrphid flies (44%), parasitic wasps (18%), predatory mites (16%) lady beetles (7%), Orius (6%), spiders (4%), predatory thrips (2%), and others (2%).
Crop pests observed on alyssum habitat plants: In the cucumber tunnels, there was a total of 815 pests counted on alyssum habitat plantings and 1226 in the tomato tunnel. In the cucumber tunnels, thrips (37%), flea beetles (29%) and tarnished plant bugs (23%), spider mites (7%), aphids (3%) and others (2%) were observed. In the tomato tunnels, the top 3 top pests followed a similar pattern with thrips (37%), flea beetles (25%) and tarnished plant bugs followed by (13%), aphids (15%) and others (2%).
It’s not surprising that there were an abundance of predatory mites on the alyssum as they were released on crops for thrips and spider mite suppression (N. cucumeris for thrips, and N. fallacis and P. persimilis for spider mites). Because floral resources are limited in these tunnels, we suspect alyssum was providing resources (pollens and attracted pests like thrips) to them. We were surprised that Orius was not more abundant on the alyssum because they were released for thrips suppression as part of the biocontrol programs that we setup for the tunnels. They are also naturally occurring but it’s impossible to tell if alyssum was drawing them in from outside. The alyssum attracted syrphid flies from outside in all tunnels. Despite the cucumber tunnels being screened, syrphid flies were frequently observed visiting the habitat plantings. The number of flea beetles and tarnished plant bugs on the plantings were an interesting, but not surprising, observation. Flea beetles are attracted to plants in the Brassicaceae family (like alyssum); however, we did not find them to be damaging crop plants nearby. We hypothesize they may have the potential to act as a trap crop for them used in this context.
Crop pests observed on bean trap plants: In the cucumber tunnels, there was a total of 3095 pests recorded from the bean trap plants and 1434 in the tomato tunnels. In both tunnels, spider mites and thrips were the primary crop pests attracted (70% and 23% respectively in the cucumber tunnels and 34% and 25% in the tomato tunnels). The bean trap plants fulfilled their intended purpose to attract spider mites. Their value as a trap plant for thrips has been overlooked and is a factor we will be looking at more closely over the next two years, especially in the cucumber tunnel. No beans were lost due to aphid damage nor from thrips infestations. However, beans were often severely damaged by spider mites where they were removed from the tunnels and replaced with new plants.
Natural enemies observed on bean trap plants: There was a total of 371 natural enemies counted on alyssum habitat plantings in the cucumber tunnel and 248 in the tomato tunnels. In the cucumber tunnels, similar to alyssum, predatory mites were the dominant natural enemy (81%). In the tomato tunnels, 37% of the natural enemies observed on beans were syrphid fly adults resting on the foliage, followed by predatory mites (19%), parasitic wasps and mummies (18%) and mummies (14%). Parasitic wasps (Aphidius spp.) were released in the tomato tunnels for aphid suppression. Because aphids were occasionally found on the beans, the wasps followed them there and parasitized them.
Arthropods on crop plants: We collected a significant amount of data from crop plants. Some of the tomato tunnels had aphid infestations at varying levels that were kept from reaching crop damaging levels through released on parasitic wasps (Aphidius spp.), the predatory midge Aphidoletes and brown lacewings. This past season was perfect for spider mites with the hot and dry summer we experienced. Spider mites damaged cucumbers in several tunnels and in some, prompted early termination of the crops in some instances, despite our IPM program. One of the research questions we are trying to answer is how much earlier can we detect spider mites on bean trap plants before we can detect them on the crop. To help answer this a subset of the crop plants that we inspected every outing were paired with bean plants in every bed. In general, spider mites were detected two weeks earlier on beans than cucumbers. One interesting observation worth noting is that in some cucumber tunnels with spider mite infestations, the plants that were adjacent to the alyssum, were noticeably healthier than plants not near an alyssum habitat plant at the end of the season. We suspect that it’s because the alyssum was harboring natural enemies that enhanced pest management on the adjacent cop plants. Tomatoes can sometimes succumb to spider mites. Tomato foliage makes it challenging to see spider mite damage early on, however, their damage is easily visible on beans. In the tomato tunnels, we did not find spider mites on tomato plants, but they did eventually show up on the beans by mid-summer. See the attached photo gallery document for some images from this past season. Progress Report 1 Photo Gallery LNE25-500R
Next steps: We are currently analyzing the crop data from year one. We are meeting with our advisory committee this winter (late February) to discuss year one results and how best to proceed in year two. We will be refining the IPM programs for spider mites in cucumbers to prevent crop losses at farms with recurring spider mite issues.
Education & outreach activities and participation summary
Educational activities:
Participation summary:
In addition to the direct on-farm learning experiences by participating farmers, this project was introduced at the 2025 Northeast High Tunnel Conference. Several slides specific to this project revealed year 1 preliminary results about the effectiveness of trap plants to pests and attractiveness of habitat plantings to beneficials.
Sullivan, C., M. Skinner, R. Bamford, S. Ghasemzadeh Dizaji, A. Tallo. Honing In On High Tunnel Habitat & Trap Plants. 2025 Northeast High Tunnel Production Conference. December 10-11, 2025, West Lebanon, NH.