Toxicity of pirimiphos-methyl and deltamethrin to Sitophilus oryzae

The overall goal of our research is to evaluate the toxicity of pirimiphos-methyl and deltamethrin to Sitophilus oryza infesting corn and other grain. Food grains and legumes comprise most of the consumed and common stored food products globally. However, insect pests such as S. oryza commonly known as rice weevil cause significant damage to stored food grains globally. This result in loss of grain quality and quantity and hence, the market value. Currently different insecticides are used to control S. oryza; however, they are known to develop resistance against some of these insecticide chemicals that are frequently used. In this study, we conducted laboratory bioassays where adult S. oryzae were exposed to two different formulations of insecticides (i.e., pirimiphos-methyl and deltamethrin) separately at different concentrations. Distilled water was used in the control group. We determined the resulting mortality of S. oryzae from single spray exposure of these pesticides at 24, 48, 72 and 96-hours after treatment. Additionally, lethal concentration of both insecticides was determined. Results from these bioassays are discussed and presented.