RESIDUAL EFFICACY OF CHLORPYRIFOS-METHYL + BIORESMETHRIN AND CHLORPYRIFOS-METHYL + RESMETHRIN FOR CONTROLLING LESSER GRAIN BORERS (COLEOPTERA, BOSTRICHIDAE), RICE WEEVILS (COLEOPTERA, CURCULIONIDAE), AND RED FLOUR BEETLES (COLEOPTERA, TENEBRIONIDAE) IN STORED WHEAT

Soft red winter wheat was treated with chlorpyrifos-methyl alone or combined with either bioresmethrin or resmethrin (synergized and nonsynergized) and stored for 10 mo under ambient conditions in Savannah, Ga. Every 2 mo, wheat was removed from storage and bioassayed with adult lesser grain borers, Rhyzopertha dominica (F.); rice weevils, Sitophilus oryzae (L.); and red flour beetles, Tribolium castaneum (Herbst). Mortality at 5 d, F1 production, percentage damaged kernels, and dockage weight after 49 d of incubation were determined. Lesser grain borers never survived introduction on wheat treated with bioresmethrin, resmethrin, or either pyrethroid combined with chlorpyrifos-methyl. Rice weevils survived on wheat treated with the pyrethroids and caused considerable damage to the wheat. Both pyrethroids suppressed red flour beetle progeny. Chlorpyrifos-methyl alone or combined with bioresmethrin or resmethrin controlled all three species and protected the wheat for at least 8 mo.