Landscape affects on soybean aphid and natural enemy abundances in Iowa

The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is a new invasive pest in soybean Glycine max here in the United States. Research has shown that a natural predator community exists here in the U.S. that is capable of suppressing the soybean aphid below economic populations. Therefore, in the course of a 3-year project from May to September, we aim to determine how landscape heterogeneity impacts the soybean aphid and it’s natural predator community. The study site was located in and around the Neal Smith National Wildlife Refuge (NSWR) located in the Southwest corner of Jasper County, Iowa. The NSWR is the largest reconstructed tallgrass prairie in the U.S. with >5,000 acres planted. In each year approximately 30 soybean fields were sampled with visual-counts, yellow-sticky cards, and sweep-net samples each week from June – September. In 2006 we found that soybean aphids have a positive response to more diverse landscapes, contrary to what we predicted. Also, predators did not respond to landscape diversity. Interestingly, 2006 had very low populations of soybean aphids (below economic levels); in contrast, in 2007 we had very high populations of aphids and initial analyses suggest aphid response to landscape varies temporally.