Protective Bioactivity of Moringa (Moringa Oleifera Lam.) Seed Oil against Callosobrochus Maculatus (F.) Infestation in Stored Cowpea (Vigna Unguiculata L. Walp.)

Protection of grains against infestation and damage by diverse storage insect pests is an age long practice, as it ensures availability of agricultural produce and guarantees food security. This study assessed the protective bioactivity of moringa (Moringa oleifera Lam.) seed oil (MSO) against infestation by Callosobruchus maculatus (F.) in stored cowpea (Vigna unguiculata L. Walp.). Ten gram grains of three cowpea varieties (Borno brown, Gwalam and Banjara) were treated with four doses (0.1, 0.2, 0.4 and 0.6 ml) of MSO in three replicates, along with un-treated check. Data obtained on the number of eggs laid, adults emerged (F1) and severity of damage were subjected to the analysis of variance (ANOVA). Mean separation at 5% probability level was performed using the Least Significant Difference (LSD). Results indicated statistical significance (P<0.05) in the mean number of eggs laid on un-treated grains compared to grains treated with higher doses from each of the varieties. Similarly, mean number of adults emerged and severity of damage from un-treated grains were statistically significant (P<0.05) relative to the treated grains with all doses of each variety. Statistical differences in the mean number of eggs laid, adult emergence and severity of damage indicated the good potential of MSO in conferring protection to stored cowpea grains. The protective effect of MSO against C. maculatus seemed to be achieved principally through oviposition suppression and reduced or complete inhibition of adult emergence, consequently reducing or eradicating infestation risk, damage and loss of cowpea grains in storage. While the use of plant essential oils against storage insect pests is being advocated, the availability, affordability and the tendency of tainting protected grains need to be considered.