In our continuing quest to take stock of the situation with soybean aphids in Illinois and elsewhere, we have surveyed several counties for presence of the aphids and kept in touch with our colleagues in adjacent states to document the distribution of this species. First, I'll provide a status report for Illinois.|
During the week of August 28, and a few days during the previous week, entomologists and plant pathologists embarked on several surveys to look for the soybean aphid. I will report the counties in which aphids were found, but I also offer a caveat. Although people who conducted the surveys found and collected aphids from soybean fields, the aphids have not been identified to species. David Voegtlin, aphid specialist with the Illinois Natural History Survey, will return shortly from a brief trip to Costa Rica, and he will identify the aphids that were collected. We suspect that the aphids we found were Aphis glycines, the soybean aphid that originated in Asia. However, if we learn differently, we will correct our report in a future update on the Web version of the Bulletin, as well as in the next print issue of the Bulletin published in October.
Our survey parameters were simple. Because all we were trying to do was detect presence or absence, we sampled only at field edges, and we examined no more than 50 leaflets per field. Leaflets on which we found aphids were placed in plastic bags with date, county, and specific location indicated. In addition, we gathered five leaves for future examination for the presence of viruses.
Glen Hartman, a plant pathologist with the USDA-ARS and the Department of Crop Sciences, found the aphid as far west as Adams, Brown, and Schuyler counties. David Onstad, a mathematical modeler in the Department of Natural Resources and Environmental Sciences, and I sampled soybean fields along or near highways 136, 67, and 150 on August 31 and found aphids in soybean fields in the following counties: Champaign, Fulton, Knox, Logan, Mason, McDonough, McLean, Peoria, Tazewell, and Warren. We didn't find a lot of aphids in any of the fields; in fact, we had to look for them carefully. But we found at least a couple of aphids in virtually every field. Matt Montgomery, Extension unit assistant in Springfield, found aphids in soybean fields in Menard and Sangamon counties. Mark Hoard, Extension educator at the Mt. Vernon Extension Center, and Robert Bellm, Extension educator at the Edwardsville Extension Center, are checking fields in southern counties to determine how far south the aphid is present.
The soybean aphid also has been found in several northern counties where the aphid was first detected in Illinois: Boone, Carroll, DeKalb, JoDaviess, Kane, Kendall, Ogle, Whiteside, and Will. Jim Morrison, Extension educator at the Rockford Extension Center, reported that on September 5 three soybean fields in Stephenson County still had aphids present, but the numbers had declined significantly since he checked them on August 27, especially in one field in which at least 50% of the leaves were yellow and ready to drop off. In the other two fields in which leaves were still green, Jim found 0 to 15 or 20 per leaflet, considerably fewer than he had observed on August 27.
It's obvious that the soybean aphid is much more widely distributed than we originally thought. Since our last report, we have learned that the aphid has been found and verified in Indiana and Ohio. There are unverified rumors of the aphid's occurrence in at least a couple of other states.
A lot of entomologists and plant pathologists are planning to learn as much as they can about the soybean aphid before the 2001 growing season. Although the soybean aphid is a new pest for us, we want to be prepared for whatever it may bring next year. Through articles in the Bulletin and other published educational materials, and at educational meetings throughout the fall and winter, we will keep you apprised of any new information we learn. In the meantime, you might want to check out the brief video we prepared when we were visiting a soybean field in Kendall County on August 22. You can view the video at http://www.ipm.uiuc.edu/ipm/index.html. Click on "!!!Special Report!!! Soybean aphids," and scroll down to the August 22 video. Many thanks are due Paul Hixson, Grear Kimmel, and Steve Parker, with Information Technology and Communication Services in the College of ACES, for their hard work and excellent ability to shoot, edit, script, narrate, and develop the video very quickly. Thanks, guys.--Kevin Steffey