Effect of temperature on residual toxicity of cyfluthrin wettable powder

Red flour beetles, Tribolium castaneum (Herbst),were exposed for 0.5, 1, an d 2 h at 20, 25, 30, and 35 degrees C on concrete treated with 100 mg/m(2) 20% (AI) cyfluthrin wettable powder (WP) at biweekly intervals for 8 wk. Kn ockdown typically averaged 80-100% at all exposure intervals and temperatur es until week 8, with no significant differences among temperatures. Althou gh the overall F-test indicated a significant difference in survival among the 3 exposure intervals, the only significant difference detected was at w eek 4. After week 0, beetles exposed at 25, 30, and 35 degrees C began to r ecover from knockdown, and by week 6 survival was at least 90%, with 1 exce ption. Survival of beetles exposed at 20 degrees C was 0.0 and 7.5% for wee ks 0 and 2, and <30% for weeks 4, 6, and 8. Beetles were able to tolerate e xposure to cyfluthrin WP at successively lower temperatures as residues age d on the concrete.