Abstract

An experiment was conducted between April to June 2014 at the Department of Zoology and Environmental Biology, University of Nigeria, Nsukka to compare the biopesticidal effects of Moringa oleifera (leaf, seed and stem bark) methanol extracts (MOLME, MOSME and MOSBME) on the oviposition and foraging rate of stored cowpea weevil (Callosobruchus maculatus) and rice weevil (Sitophilus oryzae). MOLME, MOLME and MOSBME were screened for their phytochemicals and proximate compositions. A Completely Randomized Design of five treatments (100, 200, 300 and 400 mg) replicated three times was used for each extract. Different concentrations were separately evaluated on 5 g each of cowpea and rice with three pairs of male and female of C. maculatus and S. oryzae respectively. The eggs laid by the weevils from the onset of their oviposition were counted on alternate days, while the loss in weight of the grains as a result of foraging activities was recorded. Oviposition and foraging were noted to be dependent on the concentration and duration of biopesticide. Oviposition of the two weevils varied with extract concentrations. Higher concentrations of 300 and 400 mg of MOSME and MOLME significantly decreased (p<0.5) the egg laying potentials of the two weevils when compared with their control groups. The foraging rate of C. maculatus and S. oryzae on their respective grains were significantly reduced (p<0.5) with increase in MOSME concentration when compared with MOLME and MOSBME and their control groups. The study therefore recommended the use of MOLME and MOSME, but more preferably MOSME as biopesticide in the control of C. maculatus and S. oryzae on their respective grains.