FEEDING RESPONSES OF CORN-EARWORM LARVAE (LEPIDOPTERA, NOCTUIDAE) ON CORN SILKS OF VARYING FLAVONE CONTENT

Silks of 50 field corn, Zen malls L., inbreds were evaluated in 4 sepa rate bioassays (fresh silks, 2- and 4-g oven-dried silks/100 ml diet, and silk methanol extract deposited on celufil) for their effects on t he growth of corn earworm, Helicoverpa sen (Boddie) larvae. The silks also were assayed for maysin, isomaysin, and apimaysin plus 3'-methoxy maysin content. Significant differences in larval growth were found am ong silks from inbreds within each bioassay. The dried silk bioassay w as easier to mix and dispense and permitted the use of silks of germpl asm 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 correlatio n between larval weight and apimaysin plus 3'-methoxymaysin was not si gnificant. The correlation between larval weight and total flavones fr om oven dried silks was enhanced (-0.667 for maysin alone to -0.979 fo r total flavones) compared with that between larval weight and maysin alone.