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

Abstract

A laboratory experiment was conducted to evaluate the insecticidal property of Cymbopogon citratus 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 Zea mays grains infested with 10 pairs of sexed Sitophilus zeamais 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 C. citratus extracts on weevil mortality (toxicity test) and protection of maize against S. zeamais. 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 S. zeamais. The aqueous extract gave the highest protection of the maize grains followed by chloroform, methanol and acetone extracts respectively. The insecticidal potency of C. citratus extracts and its availability places it as an attractive biopesticide in traditional post-harvest seed protection.