Iowa State Entomologists Focus on Reducing Impact of Soybean Aphids

AMES, Iowa - With soybean harvest underway across Iowa, growers are studying yields and discussing whether their crop is smaller than normal because of a relatively new pest - the soybean aphid. This invasive bug arrived from Asia in 2000, and now is well-established in Iowa and across the Midwest. Matthew O'Neal, an assistant professor of entomology at Iowa State University, is an expert on insects that attack soybeans. "Aphids have piercing sucking mouthparts and they feed on the sap of the plant," said O'Neal. "Aphid populations can grow rapidly from just a few per plant to several thousand in a short period of time. Large numbers can have a dramatic impact on yield."  If left untreated, aphids can cause soybean yield losses of 40 to 50 percent. "Growers are very concerned about this pest, and they have a lot of questions," O'Neal said. "My role is to help answer those questions in a way that protects their soybean yield." O'Neal studies a full spectrum of management tools to use against soybean aphids. "My lab works on everything from developing varieties of soybeans that are resistant to aphids, to the best and most efficient use of insecticides, to biological control and managing habitat for improved beneficial insect abundance and diversity," he said.  Aphid-resistant soybean varieties will be available for the first time for the 2010 season. "Our research shows these varieties may reduce the number of insecticide applications needed to manage soybean aphids," O'Neal said. The resistant plants will have fewer aphids compared to conventional plants, O'Neal said, but growers shouldn't expect fields to be aphid-free. "Growers will still need to regularly scout fields to determine if aphid populations exceed the economic threshold and spray accordingly," he said. O'Neal and Erin Hodgson, an assistant professor and soybean entomologist with extension responsibilities, have developed an Iowa State University Extension fact sheet that explains the development, use and limitations of the new aphid-resistant varieties. It will be distributed this fall to soybean growers across Iowa. Funding for the fact sheet and much of the soybean insect research at Iowa State has come from the Iowa Soybean Association, the North Central Soybean Research Program and other sources. Relying solely on insecticides to control soybean aphids would be a bad thing, O'Neal said. "There would be environmental costs in terms of harming non-target insects such as lady beetles and bees. But there would also be the possible loss of insecticides if harmful insects become resistant to them," he said. "So it's important for us to come up with a management plan that incorporates multiple tools."    While the main focus in recent years has been soybean aphids, work at Iowa State and other land-grant universities has been underway for many years to help develop and implement management programs for soybean insect pests that are economically and ecologically sustainable. Those ongoing efforts have resulted in two national awards that will be presented this fall to a coalition of soybean researchers across the country, including Iowa State's O'Neal and Hodgson. One award is the 2009 National Excellence In Multistate Research Award from the American Public Land-Grant Universities. The other is the 2009 Integrated Pest Management Team Award from the Entomological Foundation.