We are in the period when soybean aphid populations are increasing throughout the Midwest, so observers continue to report finding them. At some point in the near future, the focus will shift from distribution to population size. However, right now it's important to share some of the information about where soybean aphids have been found.|
In Illinois, soybean aphids have been verified in Boone and Kane counties (along with the other northern Illinois counties indicated in the previous two issues of the Bulletin). More recently, soybean aphids were found in Sanga-mon and Champaign counties. On June 28, David Voegtlin, Illinois Natural History Survey, found aphids on V3-stage soybeans in a field on the outskirts of Springfield. He found 6 aphids on one plant and 32 aphids on another plant, the latter suggesting that colonies are increasing in size. Ron Estes, Department of Natural Resources and Environmental Sciences, found two aphids in a field on the outskirts of Champaign on July 1. So, the presence of soybean aphids is confirmed in central Illinois.
Elsewhere in the Midwest, Marlin Rice, extension entomologist at Iowa State University, reported a finding of soybean aphids in far western Iowa. It's probably only a matter of time before the aphids are found in Nebraska. Doug Johnson, extension entomologist in Princeton, Kentucky, reported an unconfirmed finding of soybean aphids in Ballard County, the far western county of the state near where the Ohio and Mississippi rivers converge. To our east, Keith Waldron, with the New York State Integrated Pest Management Program, observed soybean aphids in central New York on June 20 and 27. Although he found only 1 or 2 aphids per leaflet on most plants, a few leaflets had more than 20 aphids. One plant had numerous very recently born aphid nymphs.
As you scout for the many other pests that may show up in soybean fields during July (e.g., bean leaf beetle, grasshopper, twospotted spider mite), keep watching for the buildup of soybean aphids. Actually, you spot the other pests as you sample for soybean aphids. Regardless, now more than ever, scouting in soybeans is critical. As the soybeans become reproductive, they will be vulnerable to insect and mite injury. Stay alert.--Kevin Steffey