Comparative Efficacy of Neem, False Sesame and the Physic Nut in the Protection of Stored Cowpea against the Seed Beetle Callosobruchus maculatus (F.).

Abstract

A study to evaluate the insecticidal properties of some plants was undertaken. Powder and aqueous extracts of Neem, Azadirachta indica, False sesame, Ceratotheca sesamoides and the Physic nut, Jatropha curcas were evaluated as grain protectants against the cowpea seed beetle, Callosobruchus maculatus (F.) in the laboratory at 1.5, 2.0 and 2.5 (% v/w) concentrations per 20g of cowpea seeds. Seeds of Ifebrown cowpea variety were used for the experiment. Aqueous extracts and seed powder of the plant materials were applied to the cowpea seeds using the contact method of application in the laboratory. Results revealed 2.0 % v/w and 2.5 % v/w had significant increase (P< 0.05) in adult mortality of C. maculatus in both the powder and aqueous treatments of J. curcas. Oviposition, adult emergence and percentage grain weight damage decreased significantly (P < 0.05) in a proportionate, dose dependent manner. Although C. sesamoides was the least effective when compared with the other treatments, it was significantly better than the control in the protection of stored cowpea. There was no significant difference between treatments in the germination percentage of the seeds and there was no observed discolouration of the treated seeds. All the test plant materials (Aqueous and powder) of all the test plants effectively reduced the weight loss of cowpea treated seeds with J. curcas followed by A. indica at 2.5% being the most effective. Farmers in developing countries can use J. curcas and A. indica as an alternative to chemical pesticide in rural grain storage.

Keywords: Cowpea, extracts, Callosobruchus maculatus, botanicals, Natural Pesticides, Pest Management