Effect of Second‐Brood European Corn Borer Infestation on 45 Single‐Cross Hybrids1

Plots of corn artificially infested with second‐brood corn borer egg masses were compared with plots treated with an insecticide to prevent infestation. Our studies were conducted to determine if the resistance of inbreds would be expressed in hybrids and if the present level of resistance was sufficient to prevent serious yield losses. Resistant ✕ resistant crosses were reduced in yield by second‐brood corn borer damage on the average slightly less than 4%, but the susceptible ✕ susceptible crosses were reduced in yield by 12%. Corn borer infestation decreased yield and the moisture content of the grain, but increased stalk lodging and ear droppage. The number of cavities per plant, which we used as a direct measure of resistance, increased with the susceptibility of the inbreds in the single crosses.