Bioinsecticidal Effect of Neem (Azadirachta indica A. Juss) Seed Oil on Some Cowpea (Vigna unguiculata L. Walp.) Field Insect Pests

Abstract

Cowpea is one of the important sources of relatively cheap source of protein to poor families and fodder to farm animals in West Africa  and insures food security to millions of people. This study aimed at evaluating the efficacy of neem seed oil for the management of field  insect pests of cowpea. The research was conducted in two batches of experiments at the Teaching and Research Farm, Faculty of Agriculture, University of Maiduguri. Dried Neem seeds were shelled by pounding and then winnowed to separate the kernels from the  shells. The kernels were ground into a fine powder using a mortar and pestle, then sieved through a 180µm mesh. The powder was  mixed with cold water and kneaded by hand until oil started to ooze out. The oil was then filtered and kept in a tight bottle until used for  the experiment, 5ml/1litre of water was used for the application. The treatments were laid out in a split plot design replicated three  times. Four cowpea varieties were allocated to the main plot factors and three (3) insecticidal treatments were also used as the subplot  factors in the experiment. The neem seed oil was used at weekly intervals for the treatment of cowpea plants against insect pests.  Sampling for insect pest infestations was done after each insecticide treatment once every week against insect pest which included  foliage feeders (whiteflies and aphids), flower feeders (thrips) and pod borers (legume pod borer and pod sucking bugs). Results from  this study revealed that there was no significant difference (P>0.05) between the efficacy of neem seed oil and that of cypermethrin  insecticide. Thus, there was a significant reduction in insect pest’s population which in turn increases the grain yield of cowpea. Hence,  the aqueous neem seed extract could be a good substitute for synthetic insecticide in the management of insect pest of cowpea which  could boost cowpea yield and ensuring food security.