Abstract:
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.
