Residual efficacy of spinosad-treated surfaces on Rhyzopertha dominica and Tribolium castaneum adults

Rhyzopertha dominica and Tribolium castaneum cause massive losses in stored food. These insects are effectively controlled by synthetic insecticides and fumigants but they accompany many demerits on biotic and abiotic environment. Spinosad is a bacterial formulation and a reduced-risk insecticide which is registered for stored grain protection in many countries. Despite many avenues of research on spinosad, its residual efficacy on certain insect species remains undiscovered. The objective of this research was to evaluate the residual efficacy of spinosad-treated surfaces on the survival of R. dominica and T. castaneum adults. The label rate of spinosad (25 ppm) was sprayed on polypropylene, jute, polythene, metal and filter paper. One-month-old twenty adults of R. dominica or T. castaneum were introduced on to the surfaces treated with spinosad and maintained at ambient environmental conditions. The mortality was counted at 2 and 6 days following introduction of adults. The mortality differed with the surface, insect species and duration of exposure. The current study highlights the possibility of controlling R. dominica or T. castaneum by spinosad sprayed on different surfaces.