Efficacy of liquid formulations of spinosad for controlling insectsinfesting stored wheat

Abstract: Laboratory experiments were conducted to compare the efficacies of three liquidformulations of spinosad as grain protectants on stored wheat. Evaluations were conducted ongrain that was held for 2 days and 12, 24, 36, and 48 weeks after pesticide treatments wereapplied. Bioassays for adult mortality and progeny production were conducted at 28°C and ~65%relative humidity. All three spinosad formulations effectively controlled adult Rhyzoperthadominica and prevented progeny development for 48 weeks. Overall, all of the formulations hadlimited effectiveness against Sitophilus oryzae adults and did not prevent progeny production,probably because eggs are laid inside kernels where larvae are protected from pesticide exposure.None of the liquid formulations were effective against Tribolium castaneum adults but progenyproduction was significantly lower on these treatments than on grain that was untreated. Percentegg mortality of Plodia interpunctella was similar for all treatments although overall progenyproduction was significantly less on grain treated with liquid formulations than untreated grainand through 36 weeks, grain treated with Contain and Contain II had significantly fewer progenythan grain treated with Spinosad 0.5%. The type of liquid formulation of spinosad is critical incontrolling stored grain insects.