It’s difficult to imagine, let alone count, 1,021 aphids on a single soybean plant. But in soybean fields last August, that’s what Dave Cole and Mark Myers did.

Just what impact that soybean aphids will have on your no-till soybean yields and quality is still largely unknown because the pest was only recently discovered in the U.S. In Asia where Aphis glycines originated, however, growers have suffered yield losses of up to 50 percent, says Cole.

The crop consultant and president of Independent Technical Agricultural Consulting in Prairie du Sac, Wis., credits Nancy Kurtzweil of the University of Wisconsin plant pathology department for discovering the soybean aphid in Wisconsin in July of 2000.

That same year, the soybean aphid was discovered in parts of Illinois, Michigan, Iowa and Minnesota. By 2001, it had spread to 12 states.

Studies were begun in 2000 to gain a better understanding on the effects of aphids. More studies (including research conducted by several universities and by individuals such as Cole and Myers, a technical service representative with Syngenta Crop Protection in Madison, Wis.) were conducted last year to study the pest’s effect on soybean yield and quality, and to define economic thresholds for soybean aphid control.

Wisconsin researchers report that where soybean aphid infestations and the viruses they transmit are severe, soybean yields can be reduced by 10 to 15 percent. But, there are also studies in Michigan and Minnesota that indicate yield losses can run as high as 50 percent when thousands of…