Antibiosis to Corn Earworm, Helicoverpa zea Boddie, by Cowpea Genotypes

Abstract

ABSTRACT Corn earworm (Helicovrpa zea Boddie) is a pest of cow-pea in many regions of the United States. The larvae chew round holes in cowpea pods to feed on the developing grains, and thus, affect the yield and seed quality. Studies were conducted to identify antibiosis to corn earworm (CEW) in diverse cowpea genotypes which had been identified to provide better yields in the Delmarva (Delaware, Maryland and Virginia) peninsula region. A series of bioassays were performed to evaluate the newly formed terminal trifoliolates of field grown cowpea for antibiosis to CEW. Results showed significant differences in larval weights in all bioassays. The genotypes which gave the lowest larval weights were Mississippi Silver and Quick pick Pinkeye, while the genotype, Champion, provided the largest weights of larvae in virtually all tests. Therefore, this genotype could probably be used as a susceptible check for future cowpea antibiosis studies to CEW. Results also indicate that some genotypes of cowpea that provided consistently lower weights of larvae, including Mississippi Silver and Quick pick Pinkeye, have higher levels of antibiosis to corn earworm larvae than genotypes Champion and Dixielee. These superior genotypes need to be evaluated for multiple pest resistance and other desirable agronomic traits. The antibiosis could be integrated with other methods of cowpea pest management to reduce the amount of insecticides for the management of CEW and other insect pests of cowpea.