Effect of Insecticide Spray Applications, Sowing Dates and Cultivar Resistance on Insect Pests of Cowpea in the Delmarva Region of the United States

Abstract

ABSTRACT Field studies were conducted to determine the effect of insecticide spray applications, sowing dates and cultivar resistance in diverse cowpea genotypes in the Delmarva (Delaware, Maryland and Virginia) peninsula region of the United States. A mixture of cypermethrin and dimethoate was applied in the first experiment and the number of spray applications ranged from two to six. The second experiment had two sowing date treatments and received four spray applications of endosulfan. Also, ten genotypes of cowpea were planted and observations were taken on the incidence of major insect pests and pod damage. There was a 30% increase in cowpea seed yield as a result of spraying the mixture of cypermethrin + dimethoate insecticides. The damage to cowpea pods was also significantly reduced in the sprayed treatments. The first and second sowing dates of cowpea sprayed treatments gave 30% and 45% increase in the seed yield over the first and second unsprayed dates of sowing cowpea treatments, respectively. The first sowing date treatment gave significantly higher seed yield than the second sowing date treatments. There were significant differences in the number of some major insect pests and also on pod damage among the ten diverse cowpea genotypes grown under the Delmarva field conditions. This study provides information on the incidence of insect pests of cowpea in the Delmarva region, the potential of insect pests to cause significant yield losses, and variation in insect pest resistance among ten diverse cowpea genotypes.