Characterization of pyrethroid resistance in a strain of the German cockroach (Dictyoptera: Blattellidae)

Laboratory strains of the German cockroach, Blattella germanica (L.), that were either susceptible (S, Orlando Normal) or resistant (R, Village Green) to pyrethroid insecticides were compared in studies of the topical toxicity of permethrin, as well as the in vivo penetration, metabolism, and excretion of radioactive material after topical application of sublethal doses of ( super(14)C)trans-permethrin. The objective of these tests, which were done in the presence or absence of the metabolic synergists PBO or DEF, was to obtain a better idea of the possible contribution to resistance of factors other than a previously identified kdr-like mechanism. Toxicity tests indicated the R cockroaches were highly resistant to permethrin (R/S value 38.9). Pretreatment of insects with PBO or DEF strongly increased the toxicity of permethrin to both S and R strains but did not change the level of resistance; the R/S value with PBO was 42.8 and with DEF was 41.5.