With the help of the crop systems and IPM Extension educators, the preharvest European corn borer survey is under way. The results from last year's survey indicated near historic low densities of European corn borers throughout much of Illinois. Although European corn borers didn't cause much of a fuss this season, several reports from observers in the field indicated that the second flight of moths was impressive in localized areas. As producers make their seed-selection choices this winter, we hope these data on overwintering populations of borers can be used as one factor to aid in the decision-making process. Because the harvest is under way in some areas of Illinois, don't be surprised to see Extension educators surveying fields in selected counties around the state.|
Mature European corn borer larva inside corn stalk.
Cornfield ready for harvest.
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 populations of corn borers over time. Surveyors randomly select 10 cornfields in cross sections of predesignated counties to sample for European corn borer larvae. Within each field, at least 25 to 30 paces beyond the end rows, we check 25 consecutive plants for any signs of corn borer injury (for example, frass, exit holes, broken stalks). After the number of plants infested is determined, surveyors split two infested stalks and count the borers. In a forthcoming issue of the Bulletin, we'll report our findings.--Mike Gray