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Northern Illinois Agriculture

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Soybean aphids in northern Illinois

Posted by Russel Higgins - Soybeans

Several soybean trials at the NIARC require full plant evaluation on a weekly basis. Despite observing the presence of Lady beetles for several weeks  (normally a good indicator of Sb aphids, a food source) I was unable to find aphids on the plants. That changed last Friday. While present in low numbers, Soybean aphids were easily found on plants in several trials at the NIARC. In a Bulletin article released this week Dr. Mike Gray, Extension entomologist shared the following recommendation and threshold information.

"Producers are encouraged to scout their soybean fields vigilantly over the next several weeks for soybean aphids. Cool to moderate late-summer temperatures will promote favorable conditions for aphid development and survival.

The economic threshold for soybean aphids remains at 250 aphids per plant with 80% of plants infested.  A rescue treatment through R5 (beginning seed) may prove worthwhile and should be considered. It is important to recognize that actual economic injury does not generally occur until aphids reach 675 aphids per plant. The economic threshold is designed to enable producers sufficient time to make a rescue treatment if aphid densities are increasing."

It has been several years since the Soybean aphid has been an issue in northern Illinois, but it is an insect pest that warrants attention until the crop reaches R6.

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