The efficacy of insecticides was determined in laboratory against Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (Fab.) (Coleoptera: Bostrichidae) exposed to treated shelled corn (Zea mays). Each treatment, which was composed by 1.2 kg of shelled corn, was treated with 5 ml of mixture/kg of corn using a propelling air atomizer. Fifteen days after treatment 200 g of the treated shelled corn, from each treatment, were infested with 40 adult insects of each species and this procedure was repeated every 30 days until 180 days after treatment. The number of dead insects was counted 15 days after each infestation, so the evaluations were made at 30, 60, 90, 120, 150 and 180 days after the insecticide application. After 180 days esfenvalerate + fenitrothion + piperonyl butoxide, esfenvalerate + fenitrothion and fenirothion + deltamethrin + pyperonil butoxide were effective against S. oryzae and R. dominica. Fenitrothion was effective against S. oryzae and deltamethrin + piperonyl butoxide against R. dominica. Esfenvalerate + pyperonil butoxide were ineffective against S. oryzae and the same was observed with fenitrothion against R. dominica. The use of mixtures of organophosphorus plus pyrethroids were more effective against S. oryzae and R. dominica when compared with these insecticides used alone.
Insecta; chemical control; stored product pests
