Detection of the A302S Rdi Mutation in Fipronil Bait-Selected Strains of the German Cockroitch (Dictyoptera; Blattellidae) (vol 106, pg 2167, 2013)

Extensive usage and heavy reliance on insecticides have led to the development of insecticide resistance in the German cockroach, Blattella germanica (L.).Six Þeld-collected strains of B. germanica from Singapore were used to investigate resistance to Þpronil and dieldrin.The three strains (Boat Quay, Cavenagh Road, and Ghimmoh Road) with greatest resistance to Þpronil were subjected to selection with Þpronil bait up to the F 5 generation.Synergism assay and molecular detection of a target site mutation were used to elucidate the mechanism of Þpronil resistance in these strains.With the exception of the Cavenagh Road strain, all parental strains were susceptible to dieldrin.This strain exhibited resistance to dieldrin and Þpronil with resistance ratios of 4.1 and 3.0, respectively.Piperonyl butoxide and S,S,S-tributylphosphorotrithioate were antagonistic toward Þpronil toxicity in all strains.Bait selection signiÞcantly increased Þpronil and dieldrin resistance in the three chosen strains, either in topical bioassay or bait evaluations.There was a signiÞcant positive relationship [y ϭ (6,852.69Ϯ 1,988.37)xϪ (708.93 Ϯ 1,226.28),where x ϭ Þpronil toxicity and y ϭ dieldrin toxicity] between dieldrin and Þpronil resistance levels, indicating signiÞcant cross-resistance between the insecticides.High frequencies of individuals possessing the Rdl gene mutation were found in the F 5 generation of the three strains selected with Þpronil bait.The synergism assays indicated that monooxygenase and esterase were not involved in Þpronil resistance in the strains studied herein.The A302S Rdl mutation was the major mechanism contributing to Þpronil and dieldrin resistance in these strains. KEY WORDS insecticide resistance, Þpronil,