Abstract

Three pyrethroid insecticides, cypermethrin, fenvalerate, and permethrin, were applied at 0.2, 0.5, and 1.0 g of Al/m2 to plywood panels, 12 by 12 by 0.6 cm. The panels were stored for 33 weeks at 10, 20, and 30°C and were bioassayed at these temperatures with groups of 20 adult Tribolium castaneum (Herbst) at 1, 3, 6, 13, and 33 weeks after insecticide applications. All insecticides produced high knockdown of T. castaneum at 33 weeks, with the exception of fenvalerate at 0.2 g of AI/m2, which resulted in only 26, 9.5, and 85% knockdown at 10, 20, and 30°C, respectively. None of the insecticides produced 100% mortality even at 1.0 g of Al/m2 after exposure at 1 week. Cypermethrin and fenvalerate often resulted in significantly higher mortalities at 20°C than at 10 or 30°C, whereas permethrin generally resulted in mortalities which increased with temperature. The use of these insecticides in empty granaries is unlikely, because of high cost and the high concentrations required for effective insect control.

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