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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Western corn rootworm larvae (photo: Richard C. Edwards, Purdue University,

Time to think about corn rootworms

Dr. Mike Gray, University of Illinois Entomologist, in a recent Bulletin article, pointed out that western corn rootworm (WCR) larvae are hatching earlier this spring than in the past 35 years, with an estimated hatch date of May 4-6 for central Illinois (Figure). The dry soil conditions in much of our region and early planting this spring favor WCR survival and feeding. This early hatch means that adults might also be present earlier than usual.

In several Bulletin articles last growing season Dr. Gray spoke about producers in Illinois that experienced significant rootworm damage even though they had planted a hybrid with a Bt trait. Each of these farmers had two management practices in common: 1) continuous corn and 2) planting hybrids with the same single Bt trait, Cry3Bb1. Although Dr. Gray had not yet definitively been able to conclude that the WCR populations were resistant to this particular Bt trait, an article by researchers in Iowa showed that WCR populations resistant to the Cry3Bb1 Bt trait are in Iowa.

As you are walking your fields this growing season, please contact Dr. Gray if you observe significant rootworm damage on Bt hybrids.

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