First generation corn borer adults are active in Southwestern Ontario. Scout all fields regularly for signs of activity. Look for egg masses on the undersides of the leaves and signs of pin-hole feeding (Figures 3 and 4). Plants at the whorl stage and beyond are most susceptible to corn borer damage. Use a spray threshold of 5% egg masses, or larvae or feeding injury.
To achieve optimum insecticide performance, time sprays to coincide with egg hatch or small larvae. A missed spray at this time will result in poor control for the rest of the season.