Insecticidal effect of selected medicinal plants on Sitophilus zeamais Mostschulsky in stored maize

The aim of this study was to determine the insecticidal effect and phytochemical analysis of ten medicinal plant extracts against the maize weevil, Sitophilus zeamais (Order: Coleoptera Family: Curculionidae) on stored maize by using contact and repellency bioassays together with the evaluation of the Minimum Concentration of Lethality (MCL) of highly active Annona muricata. Out of the ten medicinal plant species tested, methanol extract of Annona muricata showed the highest mortality (100%) within 7 days. Repellency bioassay was done by using a Y-shaped glass tube. Ocimum selloi showed maximum (57.80 ± 21.2) repellency for the Sitophilus zeamais, while Ailanthus altissima and Eugenia caryophylata showed significant repulsion (46.67 ± 17.6) for this insect. The highly active methanol extract of A. muricata at the concentrations of 1000, 800, 600, 400, 200, and 100 ppm was tested against Sitophilus zeamais on stored maize and a 100% mortality was observed at a minimum concentration of 600 ppm. Preliminary results suggest that medicinal plants could be exploited for the isolation of insecticidal compounds. Phytochemical analysis was performed to ensure the presence of alkaloids, flavonoids, tannins, and saponins.