EVALUATION OF NATIVE SOAP (BLACK SOAP) FOR THE CONTROL OF MAJOR INSECT PESTS AND YIELD OF COWPEA (VIGNA UNGUICULATA (L.) WALP) IN ABRAKA, DELTA STATE

Abstract

The experiments were carried out during the early and late planting seasons on a public land adjacent to Campus 2, Delta State University, Abraka, Nigeria. The study evaluated native soap at 1, 2 and 3 percent concentrations for insecticidal property in the control of cowpea insect pests, namely cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. It also assessed influence of control on cowpea yield. The result showed that native soap at 3% concentrations significantly reduced (P<0.05) A. craccivora in the early season. M. sjostedti damage, thrip population, Maruca damage and pod sucking bug were generally low in this season. In the late season, colonies of A. craccivora were reduced at 1 and 2% concentrations. Similarly, all the tested concentrations checked flower thrips. Maruca damage was slightly suppressed at 1 and 2% native soap concentrations. The control plots had the highest population of sucking bugs suggesting that native soap had effect on bugs. Yields were 1,355.90kg ha-1, 1105.20kg ha-1 and 919.80kg ha-1 for 3%, 2% and 1% soap concentration respectively in the early season. Late season grain yield were 570.80kg ha-1, 510.10kg ha-1 and 358.90kg ha-1 for 3%, 1% and 2% respectively. Based on the high yields, particularly in the early season, the study suggests that native soap can be an effective insecticide against cowpea insect pests, and could form component of the integrated pest management. It was however, observed in the field that native soap caused delay and reduction in copious cowpea flowering. Eliminating this factor could be necessary to increase the efficacy of soap in the management of cowpea insect pests.