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European Corn Borer Fall Survey Under Way

September 7, 2001
As the 2001 growing season winds down, the severity of European corn borer injury across the state remains somewhat unclear. We've received scattered reports this season of impressive moth flights in some parts of central and western Illinois counties. To more accurately assess the level of crop injury and densities of the overwintering population of borers, the 2001 survey was initiated in early September. With the help of the crop systems and IPM Extension educators, we will assess the impact of European corn borers in well over 300 cornfields and offer our statewide population and injury reports in an upcoming issue of the Bulletin. Survey results from the past two years (1999 and 2000) revealed very low densities of European corn borers throughout much of the state. As producers make their seed-selection choices this winter, we hope our survey data on overwintering populations of borers can be of some value in the decision-making process. Because the harvest is already under way in some areas of east-central Illinois, don't be surprised to see Extension educators surveying fields in selected counties around the state.

From time to time, we're asked questions concerning how the survey is performed. Because the survey always has been conducted using the same sampling procedures, we are able to compare one year with the next. European corn borers are surveyed by selecting a cross section of 10 fields throughout a county. Within each field, 25 consecutive plants are checked for any signs of corn borer injury (frass, exit holes, broken stalks). Surveyors make sure that the 25 plants are not within border rows and try to check plants 25 to 30 paces away from these field margins. After the number of plants infested is determined, two infested stalks are split and the borers are counted. County and statewide averages are then calculated regarding the percentage of plants infested and the number of borers per plant.--Mike Gray

Author: Mike Gray

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

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