Comparison of Fenitrothion and Malathion for Treatment of Plywood and Galvanized Steel Surfaces for Control of the Red Flour Beetle (Coleoptera: Tenebrionidae) and the Rusty Grain Beetle (Coleoptera: Cucujidae)1

Abstract

Fir plywood and galvanized steel panels were treated with either 0.25 or 0.50 g AI/m2 of fenitrothion or malathion spray. Panels were stored at 25 :± 2°C and bioassayed after 1, 2, 4, 8, 16, and 35 weeks with adult Tribolium castaneum (Herbst) or adult Cryptoleste ferrugineus (Stephens) using exposure periods of 1, 3, or 6 hat 30 ± 1°C, 75: t 2% RH. Insect mortality observed 3 days after exposure to insecticide was considerably higher than was knock-down immediately at the end of the exposure periods. Over 35 weeks, malathion was significantly more toxic than fenitrothion at 0.50 g AI/m2, The type of surface did not affect the relative toxicity of the chemicals except that with malathion at 0.50 g AI/m2,C. ferrugineus mortality was significantly higher on steel than on plywood. The uptake of both insecticides by rapeseed adjacent to steel surfaces was more rapid and resulted in higher residue levels than in seed adjacent to wood surfaces. Fenitrothion levels in rapeseed were consistently higher than were malathion levels. Malathion would be slightly more effective than fenitrothion for treatment of empty granaries at similar rates of application under the conditions studied.