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Title: FEEDING RESPONSES OF CORN EARWORM LARVAE (LEPIDOPTERA: NOCTUIDAE) ON CORN SILKS OF VARYING FLAVONE CONTENT

Author
item Wiseman, Billy
item Snook, Maurice
item WIDSTROM, NEIL

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The corn earworm is a perennial economic pest of field crops in the southern United States. Corn lines with resistance to the corn earworm have been identified. The resistance is due to a chemical called "maysin," or related compounds in the silks of resistant corn. Resistant corn silks can provide a biological, economical, ecological, and socially acceptable means of limiting losses by the larvae of the corn earworm. Silks of fifty corn inbreds were evaluated for feeding responses of larvae of the corn earworm in four different bioassay methods. GE37 and 91201Y silk-diets produced larvae with the lowest weights. A highly significant negative relationship was found between weight of larvae and maysin in fresh silks and isomaysin in dried silks. When all flavones from oven dried silks were combined with maysin, the correlation with weight of larvae was improved from r = -0.667 to r = -0.979. Bioassays with oven dried silk resulted in the smallest larvae, and was the easiest to mix and dispense.

Technical Abstract: Silks of 50 field corn, Zea mays L., inbreds were evaluated in four separate bioassays (fresh silks, 2- and 4-g oven-dried silks and silk methanol extract deposited on celufil) for their effects on the growth of larvae of the corn earworm, Helicoverpa zea (Boddie). The silks also were assayed for maysin, isomaysin and apimaysin plus 3'-methoxymaysin content. Significant differences in growth of larvae were found among the silks from inbreds within each of the four bioassays. 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 weight of larvae and apimaysin plus 3'-methoxymaysin was not significant. The correlation between larval weight and total flavones from oven dried silks was enhanced (-0.667 for maysin alone to -0.979).