CORN-EARWORM (LEPIDOPTERA, NOCTUIDAE) BIOLOGY ON FOOD CORN ON THE HIGH-PLAINS

This research was designed to determine corn earworm, Helicoverpa zea (Boddie), biology in irrigated food corn and identify beneficial insects and diseases associated with them. We were interested in determining the period of oviposition and feeding by com earworms to understand when com is most vulnerable to feeding damage from larvae for designing pest management tactics. These data were collected on corn during pollination and kernel development. Oviposition began with appearance of the first silks but did not peak until late July after silks were dry and continued until late in the dough growth stage. Most eggs were laid on the distal third of silks. After eclosion, larvae quickly moved to the basal third of silks usually under the husk. Larvae began feeding on kernels as third instars appeared. They penetrated 9 and 15 cm into the ear, respectively, in each of the 2 yr. Deep penetration of the ear occurred in August as kernels hardened. Larvae could not eat these hard kernels, therefore, they simply took bites out of many kernels (nipped), which lowers the quality of corn for food processing. Only 1% of the corn earworms were parasitized or infected with disease organisms.