Abundance of pest insect natural enemies in watersheds consisting of annual crop systems intercropped with perennial tallgrass prairie systems

Non-crop habitat within and around farmland can provide several benefits such as erosion reduction. Non-crop habitat may provide refuge for insects that respond negatively to disturbance regimes within annual cropping systems. In addition, many beneficial insects are attracted to flowering forbs found in prairies; to what extent their abundance and diversity in adjacent cropland is affected by this resource is not clear. Our goal is to determine how ecosystem services and biodiversity respond to the amount and placement of non-crop habitat within watersheds devoted to crop production. We hypothesize that strategic placement of small amounts of perennial habitat (reconstructed native tall grass prairie) within agriculturally-dominated watersheds have disproportionate effects on key ecosystem services and biodiversity. Insects were collected from prairie and soybeans with a sweep-net once a month beginning in May 2009 and continued until the first hard frost. In 2010, insects were collected from cornfields using a modified leaf-blower. To date we have collected over 120,000 insects representing several taxa critical for ecosystem services like pest regulation (Coccinellidae, Syrphidae, Chrysopidae, Hemerobiidae) and pollination. The abundance of natural enemies was significantly higher in prairie than in adjacent soybean fields in June and September of 2009, however the effect of the surrounding habitat of each site suggests that treatment effects were silenced. Drastic decreases in the abundance of natural enemies due to mowing prairie strips in July 2009 demonstrated the effect of disturbance on natural enemy abundance, and the ability of these communities to repopulate with increased availability of suitable habitat.