DATCP’s annual fall European corn borer survey measures the average number of corn borer larvae per plant in grain corn fields throughout Wisconsin. Survey results are used to estimate the density of the fall corn borer population and forecast the potential magnitude of the first flight of moths the following spring. Establishing where heavy corn borer infestations occur in fall indicates where excessive populations may lead to economic loss next summer.

The corn borers present during the fall survey will pass the winter as full-grown (5th instar) larvae in corn residue, pupate once temperatures exceed 50°F next spring, then emerge as adults in late May of 2004. The reproductive potential for emerging female corn borer moths is high. When conditions are favorable, each female can lay in excess of 400 eggs; thus, a sizeable fall population may develop into an economic threat in the following growing season.