Effects of current and future soybean aphid management tactics on soybean aphids (Aphis glycines) and their natural enemies in Illinois in 2007 and 2008

The soybean aphid (Aphis glycines Matsumura) is an exotic pest of soybean (Glycine max (L.) Merr.) discovered in North America in 2000. Since then, the soybean aphid has spread throughout most of the north central soybean growing region of the United States and Canada. When large populations of soybean aphids are sustained in a field, yield reductions as high as 50% may result. The objectives of this experiment were to determine the efficacy of current and future management tactics for soybean aphids and to discover the relationship between these management tactics and natural enemies of the pest in an Illinois soybean field. Management tactics evaluated were the seed-applied insecticide thiamethoxam (Cruiser, Syngenta), the foliar-applied insecticide lambda-cyhalothrin (Warrior, Syngenta), and an experimental soybean line with putative resistance to the soybean aphid (LD05-16060, University of Illinois Soybean Breeding Program). Results from 2007 indicated a trend for thiamethoxam to reduce cumulative aphid days at the end of the growing season and for LD05-16060 to accumulate fewer aphid days than its susceptible isoline. The relationship between these management tactics and natural enemies of the soybean aphid was less clear; however, natural enemies present in the experiment responded to fluctuations in soybean aphid densities. Data and interpretation will be presented from the 2007 and 2008 growing seasons.