Effect of Moringa oleifera Leaf Powder and Seed Oil on Insect Pests of Stored Maize and Cowpea

The leaf powder of Moringa oleifera was applied as direct admixture at 5g, 10g and 15g while the seed oil was applied at 5ml and 10ml to 100g each of Maize and Cowpea grains respectively, while the control was without insecticide application to test for insect mortality., progeny development and damage caused on stored maize and cowpea (Sitophilus zeamais and Callosobruchus maculatus). The experiment was laid out in a Completely Randomized Design (CRD) and results obtained were subjected to analysis of variance (ANOVA) while means were separated using the Least Significant Difference (LSD). The result showed significantly (P<0.05) progeny reduction of adult Sitophilus zeamais and Callosobruchus maculatus using Moringa oleifera leaf powder at different concentration 0, 5g (23.90, 28.62), 10g and 15g respectively. Control (0) recorded the highest number 68.51 in Callosobruchus maculatus, and 56.85 in Sitophilus zeamais. Mortality test result showed that moringa leaf powder significantly(P<0.05) increased the mortality of adult S. zeamais and C. maculatus with increase in concentration after 96 hours of exposure while moringa seed oil offered 100% mortality after 24 hours of exposure. Germination of maize and cowpea was not affected after treatment with moringa leaf powder and seed oil. Contact toxicity result showed significant adult mortality of S. zeamais and C. maculatus on filter paper with 15% mortality in C. maculatus and 10% in S. zeamais. Damage was significantly reduced in treated grains compared with the untreated control. Moringa seed oil was more toxic to S. zeamais and C. maculatus compared to moringa leaf powder and the untreated control. The protective effect of moringa seed oil against S. zeamais and C. maculatus comes principally through oviposition suppression and reduced or complete inhibition of adult emergence, consequently reducing or eradicating infestation risk, damage and loss of maize and cowpea grains in storage. While the use of plant essential oils against storage insect pest is being advocated, the availability, affordability and the tendency of tainting protected grains should be considered.