The effects of management practices on functional diversity in cucurbit production systems

Low natural enemy diversity and abundance in agroecosystems often result in detrimental pest outbreaks. Conventional agriculture often relies on application of synthetic insecticides to manage pests, while organic systems typically combine exclusion tactics and naturally-derived insecticides. Our study was designed to quantify the effects of exclusion by row covers paired with organic approved insecticides on arthropod community structure in cucurbit production systems. Effects were measured by characterizing the functional diversity of natural enemies and the abundance of the key pest species. We hypothesized that the implementation of row covers with insecticides would reduce pest abundance but would also reduce natural enemy functional diversity. Replicated fields of muskmelon and butternut squash were sampled throughout a growing season to explore these questions. The fields were divided into twelve plots and each was randomly assigned to one of three treatments: no management, row covers removed at anthesis and treated with organic approved insecticides, and row covers removed and treated with insecticides then replaced upon pollination. Although natural enemy groups varied in their response to treatments, functional diversity significantly increased throughout the season in all treatments with the highest levels in plots with no management. Conversely, pest pressure was highest in no management treatments, and each of the pest species, Acalymma vittitum, Diabrotica undecimpunctata, and Anasa tristis, responded differentially to treatments. These results underscore the challenge of managing pest complexes. Further analysis will help determine the role of natural enemies for pest management in a continued search for sustainable solutions in cucurbit systems.