Efficacy of dust formulations of spinosad for controlling insects infesting stored wheat

Laboratory experiments were conducted to compare the efficacy of three new dust formulations (B1, C3, and D1) of spinosad as grain protectants on stored wheat. Evaluations were conducted on grain that was held for 1 d and 12, 24, 39, and 52 wk after insecticide treatments were applied. Bioassays for adult mortality and progeny production were conducted at 28°C and about 65 % r.h. Dust formulations B1 and C3 effectively controlled adult Rhyzopertha dominica and prevented progeny development for 52 wk while formulation D1 was less effective. Only formulation B1 controlled Sitophilus oryzae adults (> 91% parental mortality) but did not prevent progeny production. None of the dust formulations were effective against Tribolium castaneum adults but progeny production was lower on grain treated with formulations B1 and C3. Egg mortality of Plodia interpunctella was similar for all treatments although overall progeny production was less on grain treated with formulation B1. The type of dust formulation of spinosad is critical in controlling stored grain insects