European Corn Borer: Yield Losses in Relation to Hybrid and Stage of Corn Development12

Losses in yield due to damage by Ostrinia nubilalis (Hübner) at different stages of plant development and different levels of infestation were ascertained for 4 corn hybrids, Zea mays L., commonly grown in the Midwest. Yield losses resulted primarily from physiological damage due to the corn borer infestation rather than losses due to unharvestable ears. During the whorl stage (stage 2) of plant development, yield losses per unit of infestation were greater for the susceptible, long-season hybrid than for the mid-season hybrid with an intermediate level of resistance to corn borer leaf feeding. However, the yield potential of the long-season hybrid, especially B73 × Mo 17, was great enough to compensate for the greater loss. During the pretassel (stage 4) and pollen-shedding (stage 5) stages, losses tended to be greater for the long-season than for the mid-season hybrids. B37 × Oh 43 was more tolerant to damage than the other hybrids as expressed by yield loss during these stages. Physiological yield losses tended to be lower when an infestation was initiated in stage 6 (kernels blistered), but losses due to unharvestable ears were greater.