Residual studies with cyfluthrin wettable powder:: Toxicity toward red flour beetles (Coleoptera: Tenebrionidae) exposed for short intervals on treated concrete

Red flour beetles, Tribolium castaneum (Herbst), were exposed for 0.5. 1, 2, and 4 h on concrete treated with 20% cyfluthrin wettable powder at rates of 100, 150, and 200 mg (20, 30, and 40 mg [AI]/m(2)). Beetle recovery was assessed at 0, 24, 48, and 168 h postexposure. and residual bioassays were conducted at 3-wk intervals for 24 wk after treatment. At the low application rate of 100 mg/m(2), initial knockdown after exposure increased as the exposure interval increased, but Ly week 18, 60-80% of the beetles had recovered and were mobile after 168 h postexposure. As the application rate increased to 150 and 200 mg/m(2), initial knockdown increased as the exposure interval increased, and survival decreased after 168 h postexposure. The percentage of beetles that remained mobile after they were exposed on the treated concrete was usually correlated with the percentage that were active at 168 h postexposure. Of the 18 possible concentration-exposure-recovery combinations, were described by nonlinear regression, 33 were described by linear regression, and regressions on week were not significant for the remaining 11 combinations (P greater than or equal to 0.05). The period during which survival was <10% was 3.7-10.5 times longer for beetles exposed to the maximum label rate of 200 mg/m(2) compared with the minimum label rate of 100 mg/mg(2).