Residual toxicity of cyfluthrin wettable powder against Tribolium confusum (Coleoptera: Tenebrionidae) exposed for short time intervals on concrete

Adults of Tribolium confusum du Val, the confused flour beetle, were exposed to concrete treated with 100, 150, and 200 mg cyfluthrin 20% WP (20, 30, and 40 mg[a.i.]) per m(2) for 0.5, 1.0, 2.0, and 4.0 h at tri-weekly intervals for 24 weeks after the concrete was treated. Exposure temperature was approximately 22 degrees C and relative humidity was approximately 60%. At the lowest application rate of 100 mg, the percentage of beetles that were still active after 0.5 h of exposure ranged from 78 to 100% during the study. Except for week 1, knockdown at 24 and 48 h post-exposure was at least 82%, and recovery at 168 h post-exposure was 23 to 53%. As exposure interval and application rate increased there was a corresponding decrease in both the percentage of beetles that were upright and running when they were removed from the panel and the percentage that had recovered from knockdown at 168 h post-exposure. All beetles exposed for 1.0, 2.0, and 4.0 h on concrete treated at 200 mg per m(2) were inactive at 168 h post-exposure. Of the 48 treatment combinations (four exposure times, four post-exposure observations, three application rates), only seven were significant (P < 0.05) with respect to weeks post-treatment. (C) 1998 Published by Elsevier Science Ltd.