BIOEFFICACY OF PLANT POWDERS IN THE MANAGEMENT OF COWPEA WEEVIL, Callosobruchus maculatus (F.) IN STORED COWPEA, Vigna unguiculata (L.) Walp.

Abstract

The study evaluated the insecticidal efficacy of leaf powders of four locally available plants namely, Indian jujube (Ziziphus mauritiana), Christis thron (Ziziphus spina[1]christi), Camel's foot (Piliostigma reticulatum) and Tallow tree (Detarium senegalense) against Callosobruchus maculatus (cowpea weevils) infesting cowpea seeds (Vigna unguiculata L.). Bioassay was done by direct application of each plant leaf powder using three concentrations of 1, 3 and 5 g/100 g (1%, 3% and 5% w/w, respectively) of cowpea seeds. Permethrin was added at 0.12 g/100 g cowpea seeds as standard check and untreated treatment with no plant leaf powder or synthetic insecticide served as control. Treatments were laid out in completely randomized design (CRD) with three replications. Data were subjected to analysis of variance using Genstat 17th Edition. Significant treatment means were separated using Student Newman Keuls (SNK) test at 5% level of probability. The results showed significant increase in mortality of C. maculatus at 3 % w/w treatment application (80-83%) after 7 days' exposure to leaf power of Z. mauritiana and Z. spina christis compared to the control (0.07%). Similarly, leaf powders of Z. mauritiana and Z. spina christis at 3 % w/w treatment application was the most effective in reducing oviposition (27.00), thereby bringing about a significant reduction in adult emergence (1.11-0.55), number of emergence holes (0.67) and grain damage (1.11), while it competed favourably with the synthetic insecticide (permethin). All the four plant leaf powders did not exhibit any significant negative effect on viability of the cowpea seeds tested. The results from present study showed that the plant leaf powders could be recommended for adoption by local farmers against C. maculatusinfestation and damage to their stored cowpea seeds.