Effect of Temperature on Residual Toxicity of Cyfluthrin Wettable Powder

Red flour beetles, Tribolium castaneum (Herbst), were exposed for 0.5, 1, and 2 h at 20, 25, 30, and 35°C on concrete treated with 100 mg/m2 20% (AI) cyfluthrin wettable powder (WP) at biweekly intervals for 8 wk. Knockdown typically averaged 80–100% at all exposure intervals and temperatures until week 8, with no significant differences among temperatures. Although the overall F-test indicated a significant difference in survival among the 3 exposure intervals, the only significant difference detected was at week 4. After week 0, beetles exposed at 25, 30, and 35°C began to recover from knockdown, and by week 6 survival was at least 90%, with 1 exception. Survival of beetles exposed at 20°C was 0.0 and 7.5% for weeks 0 and 2, and <30% for weeks 4, 6, and 8. Beetles were able to tolerate exposure to cyfluthrin WP at successively lower temperatures as residues aged on the concrete.