Southwestern Corn Borer Moths Common in Southern Illinois

June 2, 2000
Ron Hines, senior research specialist, Dixon Springs Agricultural Center, reported that since about mid-May, he has been capturing southwestern corn borer moths in southern Illinois. On May 9, Ron captured three moths in a pheromone trap located in Pope County. Since May 19, captures of southwestern corn borer moths in pheromone traps in Massac County have been steady. This year's first flight appears to be earlier than last season's. In 1999, Ron reported that the first flight of southwestern corn borer moths occurred on May 30 in Massac and Pope counties. By knowing when the first captures of moths occur each year, we can begin to estimate important life-cycle events for this insect pest. After 190 heat units (base 50°F) have accumulated beyond the first flight of southwestern corn borer moths, first instars can be found; second instars at 361 heat units; third instars at 533; fourth instars at 713; fifth instars at 902; pupation at 1,153; and emergence of adults at 1,321.

Each female southwestern corn borer moth deposits eggs in masses on the upper and lower surfaces of corn leaves. Female moths lay approximately 250 eggs over a 5- to 7-day life span. Eggs are yellow-green when first laid; however, after 36 hours they become cream colored with three orange-red lines on each egg. Economic infestations of the first generation of southwestern corn borers are not common, and most generally occur in corn planted near last season's infested and undisturbed corn residue. Yield losses caused by subsequent generations of this insect pest can be significant due to stalk lodging caused by the internal girdling of plants by larvae.

We'll keep you posted on future reports from Ron Hines regarding the flight activity of southwestern corn borers and other moths in southern Illinois.--Mike Gray

Author: Mike Gray