Feeding Responses of Corn Earworm Larvae (Lepidoptera: Noctuidae) on Corn Silks of Varying Flavone Content

Silks of 50 field corn, Zea mays L., inbreds were evaluated in 4 separate bioassays (fresh silks, 2- and 4-g oven-dried silks/100 inl diet, and silk methanol extract deposited on celufil) for their effects on the growth of corn earworm, Helicoverna zea (Boddie) larvae. The silks also were assayed for maysin, isomaysin, and apimaysin plus 3'-methoxymaysin content. Significant differences in larval growth were found among silks from inbreds within each bioassay. The dried silk bioassay was easier to mix and dispense and permitted the use of silks of germplasm with varying maturity. A highly significant negative relationship was found between weight of larvae and maysin content from fresh silk, and maysin and isomaysin content from oven-dried silk. The correlation between larval weight and apimaysin plus 3'-methoxymaysin was not significant. The correlation between larval weight and total flavones from oven dried silks seas enhanced (-0.667 for maysin alone to -0.979 for total flavones) compared with that between larval weight and maysin alone.