Toxicity and Repellent Activity of Momordica charantia (L.) Extracts against the Cowpea Weevil, Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae)

Olufunmilayo E. Ajayi

Abstract


Green pesticides are one of the focuses to solve environmental problems caused by the intensive use of synthetic chemical pesticides. The aim of the present study is to investigates the toxicity of acetone, n-hexane, and methanol extract of Momordica charantia (L.) leaf to adult and egg stages of Callosobruchus maculatus (Fab.) at 0, 10, 15, 20, and 25% concentrations. Repellent effect of the leaf extracts to adults was also tested at the same concentrations. Adult mortality was monitored after 24, 48, 72 and 96 h from exposure to the leaf extracts. Adult emergence from pre- and post-oviposition treated seeds was used as index of ovicidal activity of the tested extracts. The obtained data indicated that all extracts significantly (P<0.05) killed adults and inhibited adult emergence of the insect at all concentrations and exposure-periods at a concentration-dependent manner. The 25% n-hexane extract caused 100% adult mortality at 96 h after treatment. The order of extract toxicity was n-hexane > methanol >acetone. Regarding post-oviposition treated experiment, n-hexane extract caused complete inhibition of adult emergence at all concentrations while methanol and acetone extracts caused 100% inhibition of adult emergence at 15-25% concentrations. On the other hand, all extract-treated cowpea seeds in repellent tests revealed complete repellent effect against the insects. The efficacy of extracts of M. charantia in this study indicated that the plant contained some active components against the tested insect.

Keywords


Bioactivity, Callosobruchus maculatus, Momordica charantia plant extracts

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