Synergy of a trap crop and entomopathogenic nematodes for multi-generational management of flea beetles in high tunnel Brassica crops

In North America, Phyllotreta cruciferae and P. striolata, the crucifer and striped flea beetle, respectively, are significant pests of crops in the plant family Brassicaceae. Adult beetles cause “shotgun” feeding damage, which can stunt plant growth and is particularly devastating to crops with marketable foliage. The protected agriculture environment created by high tunnels allows for earlier planting dates, which can, in theory, separate young, susceptible seedlings and emerging overwintering flea beetles temporally. However, multivoltine flea beetle species quickly overwhelm cropping systems when overlapping generations result in constant presence of adult beetles. Management of flea beetles is made difficult by their high mobility, and largely relies on chemical insecticide applications, with few options for growers who use low-input practices. Entomopathogenic nematodes (EPNs) have been considered as a biological control option for soil-dwelling flea beetle larvae, but this method does not decrease damage by the initial adult generation to inhabit the crop. We propose that effective flea beetle control must interrupt host-seeking of the overwintering generation as well as decrease the impact of their progeny. Preliminary data collected in high tunnels identify the EPN species Steinernema carpocapsae as a promising candidate for control of pests in this system. This study evaluates combining the use of a Brassica juncea trap crop and application of S. carpocapsae to intercept overwintering adults, encourage oviposition outside of a collard green (B. oleracea) cash crop grown in high tunnels, and induce larval mortality through biological control.