Efficacy of <i>Cymbopogon citratus</i> Stapf leaf extract as seed protectant against <i>Sitophilus zeamais</i> Motschulsky (Coleoptera: Curculionidae) on stored maize (<i>Zea mays</i> L.)

Abstract

A laboratory experiment was conducted to evaluate the insecticidal property of <em>Cymbopogon citratus</em> leaf extract as seed protectant against maize weevil. One (1) gram each of acetone, chloroform, methanol and aqueous extracts were re-suspended in 5 ml of deionized water and used to impregnate filter papers set in four replicates. Varied concentrations of the aqueous extract per 50 g of <em>Zea mays</em> grains infested with 10 pairs of sexed <em>Sitophilus zeamais</em> for 28 days were tested for insecticidal properties and compared with experimental and synthetic conventional insecticide [Coopex (0.25 g)] controls. Parameters assessed were effect of <em>C. citratus</em> extracts on weevil mortality (toxicity test) and protection of maize against <em>S. zeamais</em>. Data obtained were analyzed using Analysis of Variance (ANOVA) and means were separated using New Duncan Multiple Range Test at 5% level of significance. Results showed significant (P < 0.05) concentration and duration dependent mortalities of <em>S. zeamais</em>. The aqueous extract gave the highest protection of the maize grains followed by chloroform, methanol and acetone extracts respectively. The insecticidal potency of <em>C. citratus</em> extracts and its availability places it as an attractive biopesticide in traditional post-harvest seed protection.