On June 1, 2005, Brian Lang, Iowa State University (ISU) Extension field specialist in crops, found soybean aphids in a soybean field near Decorah and on another field near West Union. In most cases, just one or two aphids were found on VC- and V1-stage plants, but a few small colonies of aphids were also found. In addition, Matt O'Neal, a soybean aphid researcher at ISU, found a soybean aphid nymph on a VC-stage soybean plant after looking at more than 500 plants.

Soybean aphids will colonize the upper stem and newly developing leaves on soybeans. (Marlin E. Rice)

This is the earliest date Lang has found aphids in terms of both calendar date and soybean development. For the past five years, the first aphids on soybeans in northeast Iowa have been found on June 18 (2001), June 16 (2002), June 5 (2003), June 8 (2004), and now, June 1 (2005). However, in previous years more colonies of aphids were found. "I could just be getting better at finding them as soon as they show up in soybeans," said Lang.

This soybean aphid activity in Iowa is a little earlier than anticipated, yet there is no need to get excited. It is just an initial detection of the pest and not a prediction of risk later in the season. Later this month, we will address the need to scout and accurately assess field situations to determine the presence of aphid populations.

Soybean aphids clustering on a soybean stem