Evaluation of neem (Azadirachta indica A.!Juss) seed oil obtained by different methods and neem powder for the management of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpea

Neem seed oil obtained by extraction with analytical grade acetone using a Soxhlet apparatus, NSO(S) and that obtained by the traditional kneading method, NSO(K) were compared with the powder equivalent weights (PEW, the neem seed powder capable of yielding the equivalent amounts of the oil used for the treatments) for their relative efficacy in reducing the reproductive potential of the cowpea seed bruchid, Callosobruchus maculatus in stored cowpea. Also, neem seed oil obtained by cold extraction with analytical grade acetone, NSO(C) was compared with NSO(S) and NSO(K) for their relative effectiveness in suppressing populations of C. maculatus in cowpeas treated before or after eggs had been laid on them. The two NSO formulations, NSO(S) and NSO(K) were significantly more effective in reducing oviposition and adult emergence than the neem seed powder formulation. At 50 mg/5 g seed and higher dosages, the three extracts of NSO significantly reduced egg-laying and adult emergence in pre- and post-oviposition treated cowpeas. (C) 1999 Elsevier Science Ltd. All rights reserved.