Resistant hybrids and Bacillus thuringiensis for management of European corn borer (Lepidoptera: Pyralidae) in sweet corn

Field studies done in 1991 and 1992 to determine the potential for integrating host plant resistance and Bacillus thuringiensis Berliner variety kurstaki for control of the European corn borer, Ostrinia nubilalis (Hubner), in sweet corn. Three experimental hybrids resistant to ear feeding in 1991 and 5 in 1992 were treated with encapsulated B. thuringiensis, permethrin, or left unsprayed. The commerical hybrid 'Jubilee' was included as a susceptible control. In 1991, all resistant hybrids (with and without B. thuringiensis) controlled O. nubilalis larvae as well as or better than Jubilee + permethrin, a predominant management combination in the midwestern United States. In 1992, two untreated resistant hybrids, and 4 treated with B. thuringiensis controlled total larvae as well as Jubilee + permethrin. In addition, 2 of the hybrids treated with B. thuringiensis consistently provided >95% control of late instars (3rd-5th) in the corn ear. Based on fresh market standards (no larvae or damage in ear, husk, or silk), ear protection from 4 of 5 resistant hybrids trated with B. thuringiensis did not differ from Jubilee + permethrin. Based on processing marketability (no larvae or damage on ear kernels), all 5 resistant hybrids treated with B. thuringiensis were not different from the conventional management strategy. Population densities of generalist predators did not differ between the untreated plots and those treated with B. thuringiensis; however, predator density was lower in the plots treated with permethrin. Results from this study suggest that the integration of resistant hybrids and B. thuringiensis can provide a viable alternative to insecticide-based O. nubilalis management programs for sweet corn in the upper midwerstern United States.