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European Corn Borer: First-Generation Update

June 22, 2001
So far this season, reports of European corn borer activity have been widely scattered throughout the state. In some areas of Illinois, the development of first-generation European corn borers appears to be highly variable as well. For instance, Matt Montgomery, crop systems educator, Sangamon and Menard Extension Unit, reported on June 19 that producers were finding corn borers that ranged from egg masses to those found in the midribs of corn plants. Andrew Larson, a science instructor at Black Hawk College in Kewanee, Illinois, reported on June 14 that a field of corn in Knox County was infested (30%) with European corn borer larvae (two per plant) that ranged in development from first to third instars. He also indicated that some borers had entered midribs of corn plants. As we've reported numerous times, once corn borer larvae begin to occur in midribs, in very short order, they start to tunnel into stalk tissue. Once this development takes place, rescue treatments are no longer an effective option. Producers are urged to monitor their cornfields carefully for any signs of whorl feeding and midrib injury as soon as possible in central and northern Illinois counties.

Dave Walter, Walter Seed and Fertilizer, Grand Ridge, Illinois, has a network of pheromone traps deployed in LaSalle County. Dave reported that European corn borer moth captures from June 12 through June 17 exceeded 50 moths per evening in some trapping locations. This indicates that the egg-laying process is not over and scouting for first-generation larvae should continue in earnest for much of central and northern Illinois during the latter part of June. For a detailed description of scouting procedures, biology of corn borers, first-generation management worksheets, and suggested insecticides, please refer to issue no. 10 (June 1, 2001) of the Bulletin.

For producers in southern Illinois, Ron Hines, senior research specialist, Dixon Springs Agricultural Center, indicates that the second flight of European corn borers should begin by June 26 or 27. This prediction is based on projected heat-unit accumulations from the date of initial egg laying by the first flight of European corn borer moths. We'll notify you when Ron begins to catch moths from the second flight in his pheromone traps. We appreciate your reports on European corn borer activity. Keep them coming.--Mike Gray

Scouting for first-generation European corn borers.

First-generation European corn borer whorl injury.

Determining the number of European corn borer larvae per whorl.

European corn borer midrib injury.

Author: Mike Gray

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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