Residual susceptibility of fifth instar Plodia interpunctella to cyfluthrin wettable powder

Abstract

Wandering-phase fifth instar Plodia interpuntella (Hübner) were exposed at 3-week intervals for 0.5, 1, 2, and 4 h on concrete treated with sprays of 100, 150, and 200 mg 20% cyfluthrin wettable powder (WP) per m 2 over a 15-week period. Pupation rate and adult emergence were not significantly different ( P≥0.05) with respect to exposure interval at any application rate. Of the larvae exposed at week 0 (1 day after treatment) on concrete treated with 100 mg per m 2 cyfluthrin WP, 8.7±3.8% reached the pupal stage and 3.8±1.5% emerged as adults, but adult emergence at all subsequent weeks was at least 63.8%. No adults emerged from larvae exposed at week 0 or week 3 on concrete treated with 150 mg cyfluthrin WP per m 2. Pupation and adult emergence for larvae exposed at week 0 on concrete treated with 200 mg cyflutrhin WP per m 2 was 12.7±6.8 and 11.4±6.6%, respectively, but adult emergence at week 3 was only 1.9±1.0%. Residual control, defined as the time when pupation and adult emergence were less than 10%, exceeded 3-week only at the intermediate label rate of 150 mg cyfluthrin WP per m 2.