Residual Efficacy of Certain Insecticides for Protecting Grain Stores from Infestation of Stored Product Insects

Abstract

Pesticides are relatively inexpensive and easy tool that can be used and applied for controlling stored-products insects attacking grain elevators, grain stores, flours mills and feed mills. Certain contact insecticides of low mammalian can be applied and sprayed in these stores of grains before or during storage to protect them from insect pests or to control established infestations. Four insecticides (lambda-cyhalothrin [Lambada-Magic ® 5% EC], primiphos-methyl [Actellic ® 50% EC], chlorpyrifos [Magic-phos ® 48% EC] and spinetoram [Radiant ® 12 %SC]) were tested against adults of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) , using direct contact application. The response varied with chemical insecticide, insect species and exposure time. Filter paper diffusion method at different doses was used for assaying the different tested insecticides. Spinetoram was highly toxic against T. castaneum after 24 and 48 hrs of exposure. Lambda-cyhalothrin was highly toxic against T. castaneum followed by spinetoram; chlorpyrifos and primiphos-methyl after the period of exposure of 72 hrs. Nevertheless, it could be noticed that the toxic effect of spinetoram (LC 50 =4.12ppm) was close to that of lambda-cyhalothrin (LC 50 =3.28ppm) after exposure period of 72 hrs. Spinetoram was highly toxic against S. oryzae followed by chlorpyrifos, and primiphos-methyl after 24 and 48hrs. Spinetoram was also highly toxic against S. oryzae followed by chlorpyrifos, lambda-cyhalothrin and primiphos-methyl after 72hrs. The results indicated that spinetoram as a novel insecticide is highly toxic to both the red flour beetle T. castaneum and the rice weevil S. oryzae. Implications of these results for stored product insects' management programs would be beneficial.