EVALUATION OF ELDREDGE,J.,C. POPCORN COLLECTION FOR RESISTANCE TO CORN-EARWORM, FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE), AND EUROPEAN CORN-BORER (LEPIDOPTERA, PYRALIDAE)

Discovery that popcorn (Zea mays L.) PI 340856 was resistant to corn earworm (Heliothis zea (Boddie)) led us to evaluate 34 additional lines developed by J. C. Eldredge for resistance to corn earworm, European corn borer (Ostrinia nubilalis (Hubner)), and fall armyworm (Spodoptera frugiperda J. E. Smith). The 35 lines were evaluated for corn earworm resistance in the field with artificial infestation at Ames, Iowa, and Tifton, Ga., and with natural infestation at Hermiston, Oreg. None of the lines was better than the resistant check, 'Zapalote Chico' (PI 217413), at any of the three locations. Several lines had significantly better damage ratings than the susceptible checks. A bioassay of these materials for corn earworm resistance was run in the laboratory at Ames and Tifton by adding dried maize silks to laboratory diets and monitoring insect growth and development. Six lines were evaluated as resistant at both locations. In the field at Ames, two of these six lines were rated resistant to European corn borer. Fall armyworm field resistance ratings at Tifton indicated that one line was resistant after 7 d, but it was intermediate after 14 d. The J. C. Eldredge collection of popcorns provides sources of antibiosis to corn earworm and European corn borer and is available for use by plant breeders. Corn earworm resistance may be enhanced by breeding for husk protection, which may provide an environment that will capitalize on the antibiotic factors found in the maize silks.