FIELD EVALUATIONS OF HYDROXAMIC ACIDS AS ANTIBIOSIS FACTORS IN ELITE MAIZE INBREDS TO THE WESTERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

The relationship between total hydroxamic acid content in roots of 9 i nbreds of maize, Zea mays L., and root damage by western corn rootworm , Diabrotica virgifera virgifera LeConte, larvae was investigated. Mea surements of root damage made just before adult rootworm emergence rev ealed a significant negative correlation between root damage rating an d the logarithm of total hydroxamic acid content detected Lv high-pres sure liquid chromatography. However, no correlation was found between these variables at the end of the growing season, Plant morphological factors, plant height, and total leaf count were not affected by infes tation with western corn rootworm larvae and are therefore insensitive as measurements of plant damage. Generally. relative number of days t o silk of susceptible inbreds was significantly increased with increas ing infestation with western corn rootworm larvae, but remained unaffe cted in resistant inbreds. Inbreds containing high levels of root hydr oxamates had significantly lower reductions in seed yield than inbreds containing low levels of root hydroxamates. It appears that resistanc e, in the form of antibiosis, is present in midwhorl maize inbreds to the western corn rootworm larvae and that root hydroxamic acid content may be contributing to this resistance.