Integrated Crop Management

First soybean aphids found in May

Our first official sighting of soybean aphids occurred in soybeans on May 31 near Ames in Story County. Students in the Soybean Entomology Research Laboratory found several winged aphids and a few colonies on V3-stage soybeans. One colony had about 40 aphids, indicating that the aphids had probably been there for about a week. The following day, soybeans were inspected at McNay Research and Demonstration Farm, Lucas County, and Northeast Research and Demonstration Farm, Floyd County, but no soybean aphids were found in those research plots.

To put this in perspective, last year we found our first soybean aphids in Lucas County on June 1. However, the population in this field reached a peak of less than 250 aphids per plant, which is below the economic threshold. So an early arrival of aphids in soybeans does not forecast a looming disaster in July or August. Many factors, such as weather, soybean hybrid, and beneficial predators, will influence the development of aphid populations during the next two months. We will keep you updated on our findings and aphid populations around the state.

Winged soybean aphid [1]
Winged soybean aphids fly from buckthorn to soybean where they give birth to live aphids. (Marlin E. Rice)

This article originally appeared on page 158 of the IC-496(14) -- June 5, 2006 issue.

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