Synergistic effects of entomopathogenic nematodes and trap cropping on adult and larval flea beetle population

Commodities

Practices

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 (EPNs) 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 EPNs 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.  

This project aims to develop a technique for controlling flea beetles in high tunnel Brassica crops using a combination of EPNs and trap crops. EPN applications for flea beetle control will be two-fold, treating both the larvae in the soil within the tunnel, as well as adults that encounter wild turnip trap crops grown outside the tunnel. Evaluation will assess persistence of EPNs through waxworm bioassays on collected soil samples and assess flea beetle control through observations of foliar damage. This project will introduce a novel and more comprehensive method of pest control for flea beetles in organic and low-input production, targeting multiple life stages of the pest and thus providing more complete crop protection. Establishment of trap crops and soil management practices to increase persistence of EPNs can decrease labor and expenses dedicated to control flea beetles.  

Anecdotal accounts from surveyed growers in Indiana identify flea beetles as one of the most economically important, damaging, and difficult to control insect pests in high tunnel production systems. Successful implementation of a system that decreases pest pressures from flea beetles in multiple life stages would benefit growers across the state and region. From the results of the project, growers who struggle with control of flea beetles will gain knowledge on the use of EPNs for biological control as well as a deeper understanding of the flea beetle life cycle, behavior, and additional means of control beyond typical exclusion or treatment within the crop system. With this new knowledge, growers may be inclined to focus attention on the landscape outside of their high tunnels and main crop fields, identifying potential locations to include trap crops and to apply EPNs. Growers that traditionally use pesticides to control flea beetles may be interested in trying a newer, low-input approach. Outcomes can be measured by the proportion of growers that intend or take action to implement biological control measures outside of the high tunnel. Growers may also be inclined to alter the landscape surrounding high tunnels, to either effectively practice trap-cropping, or to eliminate locations of refuge for pests that are not easily managed. Outcomes will be assessed quantitatively by distribution of surveys to growers to indicate interest in implementing this practice in and around their high tunnels.