Bye-Bye Corn Borer

Where did all of the European corn borers go? The "late-night-driving-down-country-lanes windshield moth test” should have been a clue that something was up.

University of Illinois Extension entomologist Mike Gray confirms that there were very few corn borers found in the state in 2009, especially compared with the year prior to Bt use in the mid-1990s.

"The result of our 2009 statewide survey is stunning,” Gray says. "Only 1.2% of the corn plants in the study showed any sign of corn borer injury. The number of second-generation European corn borer was reduced to fewer than one [0.6] borer per 100 corn plants.”

Gray says no borers were found in 23 of the 48 counties sampled. The highest record in the past 11 years for the state was in 2002, when 49% of plants were infested and samplers found 95 borers per 100 plants.

Surveyors didn't distinguish between refuge and nonrefuge corn acres. Fields were chosen at random.

"European corn borers have been unable to survive, thanks to Bt corn,” Gray says. "As refuges decrease in size and additional Bt hybrids with pyramided genes expressing multiple Cry proteins come to the market, European corn borer densities will likely continue their decline.”

He expects the spring 2010 moth flight to be quite low. "These numbers suggest that this once prominent insect pest of corn has been reduced to nearly an insignificant threat,” Gray adds.

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