Evaluation of native soap (local black soap) for the control of major insect pests and yield of cowpea (Vigna unguiculata (L) WALP in ASABA, Southern Nigeria

Abstract

Three concentrations of native soap namely 1, 2 and 3 percent were evaluated for the control of four major insect pests and yield of cowpea. The insect pests studied were the cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. The experiments were conducted in the early and late planting seasons in the Teaching and Research Farms of the Agronomy Department, Asaba Campus, Delta State University, southern Nigeria. Effect of chemicals on insect pests indicated that M. sjostedti damage was prevented at all the tested soap concentrations. Similarly, at 2% concentration, Maruca population was reduced in the early season. During the late season, all the tested soap concentrations effectively controlled A. craccivora and pod sucking bugs. At 1% concentration, M. sjostedti was effectively checked. On grain yield, the figures suggested that native soap was an insecticide for pest control in cowpea production. In particular, 2% and 1% concentrations gave cowpea yield of 570.00kg ha -1 and 547.90kg ha -1 respectively in the early season. It was observed however, that during the study, native soap had an inhibitory property by delaying and reducing copious flowering in cowpea. In the late season, yield were relatively low in all the soap treatments due to very low rain. The study suggests that (1) native soap is an effective bio-pesticide against cowpea insect pests (2) more grain yield could be obtained if the inhibitory factor in native soap is removed; local cowpea growers may prefer it to synthetic chemicals, since this could save cost and pose less hazards to health.