Potentials of Calotropis gigantea and Allamanda cathartica in controlling Callosobruchus maculatus in stored cowpea


Department of Crop Protection, Entomology Unit, Faculty of Agriculture, University of Ilorin, PMB 1515 Ilorin, Nigeria

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Use of synthetic insecticides in storage of grains has resulted in hazards to man, animals and environment. Resurgence of pest resistance also occurred which led to search for alternative means for pest control. This study was carried out to evaluate efficacy of powdered, aqueous and solvent extracts of Calotropis gigantea and Allamanda cathartica in control of Callosobruchus maculatus in stored cowpea and determine phytochemical constituents of C. gigantea and A. cathartica. The experiment was carried out in the laboratory of Department of Crop Protection using a Completely Randomized Design. Eleven (11) treatments applied at 3 rates i.e. 2ml, 4ml and 6ml for aqueous and ethanol extracts and 2g, 4g and 6g for powder. Cowpea variety IT96D-610 was used for the study. Powder, aqueous and ethanol extracts were prepared from mature air-dried leaves of C. gigantea and A. cathartica. Treatments were applied to 50g of cowpea seeds and replicated 3 times. Ten (10) adults of C maculatus ratio 1:1 were introduced into each replicate. Parameters used to assess efficacy of treatments were; adult mortality, oviposition rate, larvae and pupae emergence, F1 progeny emergence, weight loss and seed viability. Findings show leaves of both plants contain alkaloids, cardiac glycosides, tannin, saponin, anthocyanins, steroids, coumarins and terpenoids. The extract of A. cathartica at 6ml/50g was most effective in control of stored cowpea seeds. and can be used successfully in the storage of cowpea seeds by resource poor farmers in Ilorin.

Keywords: Bio-pesticides, bruchid, efficacy, storage.