Tuesday, 8 November 2005
3

Antibiosis in Cowpea Genotypes for Corn Earworm (Helicoverpa Zea Boddie).

Fawzy M. Hashem, Robert Dadson, Iqbal Javaid, and Jagmohan Joshi. University of Maryland Eastern Shore, Department of Agriculture, Trigg Hall, Princess Anne, MN 21853

Corn earworm is a potential pest of cowpea in the United States. Crop resistance is one of the strategies which could be used for the management of this insect pest in cowpea. A study was conducted to evaluate 22 diverse cowpea genotypes for antibiosis type of resistance to corn earworm grown in a replicated field trial. Neonatal larvae of corn earworm were reared on newly formed top leaflet of each genotype in the Delmarva Peninsula region of the US. There were significant differences in each test in the weights of larvae after 10 days of rearing on of the leaves of various cowpea genotypes. The cowpea genotypes on which the larvae weighed heavy were regarded as susceptible and those on which they weighed the lowest were regarded as having higher degree of antibiosis. Genotypes Champion, Texas Cream 12, Texas Cream 6, California Blackeye 5 and California Blackeye 46 were found to be significantly susceptible compared with the other genotypes tested. Genotypes Colossus and Quickpick Pinkeye showed higher antibiosis type of resistance and were not significantly different from most of the genotypes included in this studies. Those genotypes which have shown some antibiosis type of resistance to corn earworm need to be evaluated for multiple insect pest resistance in cowpea.

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