Submitted to: Journal of Agricultural and Urban Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 7, 1996
Publication Date: N/A
Interpretive Summary: The corn earworm is a perennial economic pest of field crops in the southern United States. Resistant corn silks can provide a biological, economical, ecological, and socially acceptable means of limiting losses by the corn earworm. The effect of silk from numerous commercial hybrids of corn on weight of larvae of the corn earworm reared on silk-diets was studied. The flavone content of silk from each hybrid was determined. We found that Hyperformer HS9704, Stanford S88B, N C + X6485, Zimmerman Z63W, Pioneer 3140, Ag America 6714, and ICI Garst H8285 possessed high silk antibiosis against the larvae of the corn earworm. A highly significant relationship was found between low weight of larvae and high content of maysin and chlorogenic acid in the silks. This information on the antibiotic effects of silks on larvae of the corn earworm indicates that some commercial companies already possess hybrids with high levels of antibiosis against larvae of the corn earworm.
Silks of commercial corn hybrids (ranging in maturity from 60-65 days to mid-silk) were evaluated against feeding response of corn earworm, Helicoverpa zea (Boddie) (CEW) larvae. Flavone (maysin, chlorogenic acid, and apimaysin plus 3'methoxymaysin) content was determined for each hybrid from 2-d-old pollinated silks. Significant (P<0.05) differences among hybrids were found in the weight of larvae fed silk-diets of the commercial hybrids. In 50 of 74 comparisons, larvae that fed on silk-diets with formalin weighed significantly (P<0.05) more than those that fed on silk-diets without formalin. Consistent, significant (P<0.05) negative correlations were found between weight of larvae feeding on silk-diets with and without formalin and maysin and chlorogenic acid among all 4 commercial corn hybrid maturity groups, but not for apimaysin plus 3'methoxymaysin. Several hybrids (Hyperformer HS9843, Stanford S88B, N C + X6485, Zimmerman Z63W, Pioneer 3140, Ag America 6714, and ICI Garst H8285) had silks that exhibited high antibiosis against CEW larvae. Silks of some hybrids contained insufficient maysin or other flavones to account for the reduction in larval growth, i.e., N C + X6485 and Zimmerman Z63W, and SSI UTN 318.