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The Search for Soybean Aphids in Soybean Fields Begins

June 21, 2002
We haven't said much about soybean aphids this spring because there hasn't been much to report. However, with the first findings of soybean aphids in soybean fields in Illinois, Iowa, Michigan, Minnesota, and Wisconsin, it's time to start watching more closely.

The first two reports of soybean aphids in soybean fields this year came from Michigan and Wisconsin. In the June 13, 2002, issue of Michigan State University's Field Crop Advisory Team Alert, entomologist Chris DiFonzo reported finding soybean aphids in soybean during the week of June 10. The aphids were found in East Lansing and in Saginaw County at the Beet and Bean research farm. Following is a quote from her article: "Judging by the largest aphids found, colonization began about June 5-6." In the June 13, 2002, issue of Wisconsin Crop Manager, entomologist John Wedberg reported that David Hogg's crew also found soybean aphids in soybean during the week of June 10, close to their first detection in 2001 (June 15). Following is a quote from John's article: "Two years' experience has failed to show threatening levels of aphids in V0-V1 soybean, but it's still worth spot checking these seedling beans."

The Minnesota Department of Agriculture reported finding soybean aphids in a soybean field in Houston County (extreme southeastern Minnesota) on June 12. Approximately 50% of the plants were infested with one to two aphids each. This field was the only field among 195 fields sampled in which aphids were found.

More recently, someone in Iowa reported finding soybean aphids in a soybean field in Winneshiek County. This report has been registered at the Web site "2002 Soybean Aphid Watch": This Web site has expanded from last year to include all of eastern North America. The big map on the front page of the Web site shows all of the counties in eastern North America. Counties in which soybean aphids in soybean fields have been reported are red. Navigate to the area of interest by clicking an individual state or province. To view all of the reports submitted from a county or division, click on the appropriate administrative unit on the map. There are links to other sites, too. You can access the 2001 data, information on soybean aphids, and diseases that they transmit using the navigation menu.

Most important for producers in Illinois, soybean aphids were found for the first time in Illinois this year on June 19 in Kendall County. Ron Estes, research specialist in agriculture in the Department of Natural Resources and Environmental Sciences, sampled 30 V1-V2 stage plants in the field and found aphids on two of the plants--only 1 aphid on one plant and a small colony of about 12 aphids on the other plant. Aphids have begun their annual movement from their primary host (buckthorn, Rhamnus spp.) to soybeans throughout the upper Midwest, so it's time to start watching them closely. At least a couple of teams of folks from the University of Illinois will be searching in northern counties during the next couple of weeks, and we will report our findings in future issues of the Bulletin. Don't hesitate to contact us if you think they have found them.

As we have stated previously, we really don't know whether soybean aphids will reach economic levels in 2002. However, the lateness of planting of soybeans this year might have an impact on soybean aphids this year; later-planted soybeans are more likely to suffer economic damage caused by soybean aphids.

We have developed a fact sheet that includes updated information about soybean aphids in Illinois. You can view it on the Web at agriculture/soybeans/nsrl_4.pdf. If you want a paper copy of the fact sheet, please contact your local Extension office or contact Extension Entomology, Department of Crop Sciences, University of Illinois, S-318 Turner Hall, 1102 South Goodwin Avenue, Urbana, IL 61801; telephone (217)333-6652.

We'll do our best to keep you informed about soybean aphids throughout Illinois and elsewhere this year.--Kevin Steffey

Author: Kevin Steffey

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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