Residual susceptibility of fifth instar Plodia interpunctella to cyfluthrin wettable powder

Wandering-phase fifth instar Plodia interpuntella (Hubner) 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 diff erent (P greater than or equal to 0.05) with respect to exposure interval a t any application rate. Of the larvae exposed at week 0 (1 day after treatm ent) on concrete treated with 100 mg per m(2) cyfluthrin WP, 8.7 +/- 3.8% r eached the pupal stage and 3.8 +/- 1.5% emerged as adults, but adult emerge nce at all subsequent weeks was at least 63.8%. No adults emerged from larv ae exposed at week 0 or week 3 on concrete treated with 150 mg cyfluthrin W P per m(2). Pupation and adult emergence for larvae exposed at week 0 on co ncrete 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). (C) 1998 Elsevier Science Ltd. All rights re served.