Plant Oils to ControlSitophilus zeamaisMotschulsky

Abstract

The maize weevil, Sitophilus zeamais Motschulsky, is the most important pest of stored maize, Zea mays L. The pest causes estimated losses of 5–10% worldwide. Oil extracts from plants show promise to control maize weevil with important advantages over conventional insecticide, such as non-toxicity to humans, biodegradability, and ecosystem safety. The objective of this research on maize weevils in laboratory conditions was to determine the insecticidal effect of 10 plant oils: garlic, Allium sativum L.; cinnamon, Cinnamomum verum J.; hot pepper, Capsicum annuum L.; clove, Syzygium aromaticum L.; mint, Mentha piperita L.; black pepper, Piper nigrum L.; rosemary, Rosmarinus officinalis L.; rue, Ruta graveolens L.; thyme, Thymus vulgaris L. and allyl (commercial product). Residual film was used to test plant oils at five concentrations: 9,000, 7,000, 5,000, 3,000, and 1,000 ppm. The number of weevils killed was counted at 72 hours, and treatment means were compared using a Tukey multiple separation test. PC-Probit analysis determined LC50 and LC95. Most weevils, 52.47 and 60.38%, were killed by garlic and black pepper oils, respectively; at 9,000 ppm; fewer than 50% were killed with the other plant oils. Use of garlic and black pepper oil might be an alternative method to manage this insect pest in stored maize.