Do reconstructed prairies affect predation rates of soybean aphids (Aphis glycines) at the watershed scale?

Reconstruction of perennial native plants (i.e. prairie) around annual crop production can deliver ecosystem services, including water purification, carbon sequestration, and biological control. The amount and configuration of perennial habitat affects the delivery of ecosystem services to crops. An ongoing study at Neil Smith National Wildlife Refuge in Iowa has investigated the contribution of varying configurations and quantities of prairie reconstructions to ecosystem services in small watersheds in a corn-soybean rotation. The replicated treatments include watersheds without prairie, 10% of the land in prairie located at the base of the watershed, and 10 or 20% of the land in prairie distributed throughout the watershed. Our initial surveys of the insect natural enemy communities within the experimental watershed during 2009 suggest that though more natural enemies were present in prairie than the adjacent soybean fields, there is no treatment difference in natural enemy abundance in crop fields. During the 2011 growing season, we will determine if the adjacent prairie will increase predation rates of soybean aphid (Hemiptera: Aphididae). We hypothesize that predation rates will vary among experimental watersheds, with changes in prairie quantity and distribution. To test this hypothesis, we will compare caged and uncaged soybean plants and monitor predation rates of soybean aphids during a two-week period in July. We hypothesize that predation rates will increase with proximity to prairie edge, which will be tested using transects with caged and uncaged soybean plants in the soybean row adjacent to prairie and 50 meters from the edge of the prairie.