Project Overview
Commodities
- Agronomic: mustard
- Vegetables: greens (leafy)
Practices
- Crop Production: high tunnels or hoop houses
- Education and Training: extension, on-farm/ranch research
- Pest Management: biological control, trap crops
- Production Systems: agroecosystems, organic agriculture
Abstract:
Flea beetles (Coleoptera: Chrysomelidae) are major agricultural pests, feeding on Brassica vegetables, greens, and solanaceous crops. Their larvae are minor root pests, while adult foliar feeding leaves characteristic shotgun patterned damage, often significantly reducing crop quality and yield. Current control measures include insecticides and exclusion netting to prevent adult feeding. However, due to the small size of these insects, fine netting poses additional issues, including temperature extremes and exclusion of beneficial insects. Additionally, netting does not protect the crop from newly emerging adults from the root zone. While chemical pesticides can knock down flea beetle populations, there are few options for organic growers when controlling this pest.
Biological control is an option for growers who focus on sustainable farming methods and reducing pesticide use. Currently, several commercially available species of entomopathogenic nematodes (EPN) are recommended for control of flea beetle larvae. However, this technique fails to address the high mobility of adult beetles, which emerge from overwintering locations and disperse into the crop. Thus, applications of EPN at the crop root zone alone have little effect on foliar damage. Because of this overwintering behavior, trap cropping to intercept adult beetles seeking hosts in early spring has also been used. Trap crops alone may reduce feeding damage on the main crop but fail to reduce pest populations without pesticide application. While some organic pesticides are registered for use against flea beetles, efficacy when treating the trap crop alone remains low. These outcomes suggest that management of flea beetles must provide control within the crop and in the landscape, attacking multiple life stages.
To address this problem, we aimed to develop a technique for controlling flea beetles in high tunnel Brassica crops using a combination of EPN and trap crops. We hypothesized that the cultural control provided by the trap crop would interact with the biological control services provided by EPN in a synergistic manner; i.e., adult flea beetles would be intercepted by and preferentially feed and oviposit on the trap crop, increasing effectiveness of the targeted EPN application to the soil to treat flea beetle larvae. Specifically, we used commercial EPN products that are readily available to growers, rather than lab strains that are used in a lot of EPN research. This management strategy is sustainable, requires low-inputs, and is compatible with organic production, all while targeting multiple life stages of the pest and providing more complete crop protection.
Our evaluation included experiments conducted in the greenhouse, at research high tunnels at Meigs Horticultural Farm, part of Throckmorton Purdue Agricultural Center in Lafayette, IN, as well as on-farm, working closely with high tunnel grower collaborators. We implemented this trap crop and EPN system first in the greenhouse at a small scale, to assess beetle feeding preferences to affirm trap crop choice, and determine the effect of EPN applications on soil-dwelling flea beetle larvae. In the high tunnels, we implemented the trap crop design at a larger scale, placing the trap along the entire length of the high tunnel to physically intercept beetles. Our data collection included sticky card and visual observation counts of adult flea beetles, and feeding damage assessment.
Our educational approach to this project includes not only close work and on-farm demonstrations with grower collaborators, but presenting to and communicating with larger grower audiences in order to increase the dissemination of our experimental findings. Over the course of the project, we shared information with a total of over 100 attendees of grower conferences and field day demonstrations, and reached further audiences through an online extension bulletin. We worked most closely with our grower collaborators and their farm support staff, who demonstrated interest in adopting trap cropping, EPN, or both, to their high tunnel cropping systems.
Our findings from this project ultimately support the use of trap cropping to prevent feeding damage to high tunnel Brassica crops. However, the data we collected in this project as well as the current literature suggest that EPN have potential to be an effective tool for controlling flea beetles, but we plan to continue to investigate this specifically in Brassica specialty crop systems beyond the timeline of this project. Beyond the immediate scope of the project, we opened a conversation with growers about allocating high tunnel or adjacent space for non-crop plantings, including companion plantings that support other natural enemies, to ultimately minimize the use of insecticides. All growers at collaborating farms plan, to some extent, to adopt a similar system in their Brassica crops to prevent feeding damage from flea beetles. Additionally, non-collaborating growers who were audience members at field days and grower conferences showed interest in adopting some of these practices, even to different cropping systems.
Project objectives:
Flea beetles are routinely identified by growers as a major pest, resulting in economic loss throughout most of the growing season. The ultimate goal of this project is to investigate means to decrease flea beetle pressures on Brassica crops and develop a system that is low-input and easily adapted by high tunnel growers. To address this problem, our research objectives are as follows:
Objective 1: Assess efficacy of Brassica juncea trap crop in combination with commercially available EPN species.
To begin the project, work conducted in the greenhouse and at the research farm will investigate the trap crop system and effectiveness of commercial EPN products to control flea beetles.
Objective 2: Cater low-input multi-generation control of flea beetles to grower high tunnels.
In the second half of the project, we will work with growers to modify the trap crop system to best meet their individual needs, and implement the system at their high tunnels, to test these management approaches in a less controlled environment than the research farm.