This project leveraged agricultural diversity to mitigate the recent attack of the invasive yellow-margined leaf beetle (Microtheca ochroloma) on leafy brassica greens across the Southeastern United States. This new pest is reviled among farmers in Alabama, Florida, Georgia and South Carolina, is rapidly expanding its range northward as winters become milder. Unfortunately, the biology of M. ochroloma is not well known, and organic farmers have not found a viable tool for protecting their brassica crops. However, strong host plant preferences revealed by M. ochroloma suggest that it might be successfully manipulated with strategic combinations of attractive trap crops and repellant intercrops. Our project focused on identifying companion plants that reduce destruction by M. ochroloma in the absence of other viable tools. We tested three methods to control Microtheca ochroloma, including intercropping, trap cropping, and biological control via predator gut content analysis. Our purpose was to identify accessible strategies that limit damage from this pest while minimizing pesticide use on organic farms. First, we found that lemongrass and tomato companion plants may reduce herbivore populations on turnip greens while commonly employed companion plants like basil and marigold may actually backfire to attract herbivores, relative to crop monocultures. Predatory insects were highly correlated with herbivore populations; suggesting that they are more influenced prey availability than companion plants. Next, we found that mizuna is a strongly preferred host plant by M. ochroloma, relative to other Brassica napa hosts, but may only serve as an appropriate trap if pest spillover is managed. Last, we identified several generalist predators that commonly consume M. ochroloma that were unknown previously by screening predator guts for M. ochroloma DNA.
