No. 14 Article 4/June 30, 2006

Keep Watching Closely for Soybean Aphids

The results from our weekly survey of 26 soybean fields in Woodford County (10 fields); Marshall, Putnam, Bureau, Lee, Whiteside, and Ogle counties (1 field in each county); and Stephenson County once again revealed low numbers of soybean aphids in the fields surveyed. However, the surveyors found relatively large colonies of soybean aphids on selected plants in a field in Woodford County and a field in Stephenson County. In Woodford County, the surveyors counted more than 200 aphids per plant on two plants and more than 100 aphids on another plant. The average density of aphids for the field (20 plants sampled) was well below the threshold of 250 aphids per plant, but the observation of larger colonies bears watching. Fortunately, multicolored Asian lady beetles were active in the field. In Stephenson County, the surveyors counted 72 aphids on one plant in one field.

The recent return to lower temperatures will favor growth and development of soybean aphids. So despite the slow start and reports of low numbers of the pest throughout the Midwest, vigilance is imperative if we hope to stay on top of the situation.--Kevin Steffey

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