Persistence and Uptake in Wheat of Malathion and Bromophos Applied on Granary Surfaces to Control the Red Flour Beetle12

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Abstract
Malathion EC and bromophos wp were diluted with water and applied at 0.05 liter/m2 to provide a deposit of one g/m2 AI on concrete, metal, fir plywood, and maple hardwood floor surfaces in a farm granary. The rate of uptake of each insecticide in wheat, in contact with the treated hardwood floor, was determined by analysis of core samples. Insecticide persistence on treated surfaces was assessed by 24-h exposures of adults of Tribolium castaneum (Herbst) from 1–40 wk after treatment. Both insecticides provided 100% mortality on metal surfaces for 40 weeks. Malathion provided 100% mortality on fir plywood for 40 wk and on the maple hardwood floor for 4 weeks. Bromophos provided 100% mortality on fir plywood for 18 wk and on the maple hardwood floor and concrete for 4 weeks. Malathion showed no increased uptake in stored wheat after 4 wk but bromophos showed increased uptake from 0.28 ppm after 18 wk storage to 0.47 ppm after 40 weeks. The experiments indicated that malathion and bromophos need not be applied as frequently to granary surfaces of metal and wood as to those of concrete.