Insecticidal Evaluation of Some Plant Materials as Grain Protectants Against the Maize Weevil, Sitophilus zeamais (Mots) (Coleoptera: Curclionidae)
Laboratory experiments were carried out to investigate the efficacy of ethanolic extract of four plant materials, namely: Zanthoxylum xanthoxyloides (Lam.) Waterm., Aristolochia ringens(Vahl), Colocasia esculenta (L.) Schott and Morinda lucida (L) on the maize weevil Sitophilus zeamais (Mots). Parameters assessed were adults toxicity, adult emergence, percentage of reduction of plants and damage effect of weevils to the grains at 0.0, 1.0, 1.5 and 2.0% (w/v) concentrations. Zanthoxylum xanthoxyloides evoked 100% adult mortality within 24 h after treatment; and A. ringens also significantly caused 100% mortality within 48 h. Aristolochia ringens at all concentrations provided good protection to the grains stored for 49 days and also gave 100% reduction value as well as 0.00% damage and 0.00 Weevil Perforation Index. This study therefore revealed the grain protectant ability of A .ringens and Z. xanthoxyloides on the maize weevil, Sithophlius zeamais. The bioassay procedure used and results obtained are reported.