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Northern Illinois Agriculture

University of Illinois Extension
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A week in the nineties!

Thankfully the weather is about to break, most northern Illinois crops appear to have weathered this past weeks temperatures well. Dr. Emerson Nafziger has stated that corn plants can withstand warm temperatures into the nineties, if soil moisture is not limiting. A lesson learned from 2012. This week at the NIARC our wheat variety trials were harvested, treatments were applied to several studies including high yield soybeans. I had the opportunity to make several farm visits and traveled through areas of substantial Japanese beetle numbers. This was ascertained by the number of beetles bouncing off my windshield and the leaf feeding taking place on soybean.


In Illinois Japanese beetles have one generation per year and have a wide host range, feeding on over 300 species of plants including soybean and corn, (especially corn silks). The economic threshold for this insect in soybean is 20% defoliation after the soybean is in full bloom and for corn


  1. there are there are 3 or more beetles per ear,

  2. silks have been clipped to less than ½ inch,  and

  3. pollination is less than 50% complete

Very importantly, when scouting for Japanese beetle, be aware of their propensity to congregate. Scout a minimum of five locations wthin a field to assess an economic threshold.

Visit this site for additional information on the Japanese beetle in Illinois.

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