Insecticide resistance profiles and possible underlying mechanisms in German cockroaches, Blattella germanica (Linnaeus) (Dictyoptera: Blattellidae) from Peninsular Malaysia

摘要

Insecticide resistance and possible underlying mechanisms were studied in 52 strains of the German cockroach, Blattella germanica (L.) field-collected from Peninsular Malaysia. These strains were assayed using a lethal time assay at 10x susceptible LC_(95) concentrations of propoxur (1.10 mu g/cm~2), chlorpyrifos (18.40 mu g/cm~2), permethrin (1.70 mu g/cm~2) and deltamethrin (0.55 mu g/cm~2) using a surface-contact exposure method with reference to the susceptible ICI strain. Results indicated thatpropoxur and permethrin resistance were highly prevalent (73.0% and 80.2% of LT_50 RR > l0x, respectively) while low prevalence of deltamethrin (29.6%) and chlorpyrifos (4.0%) resistance (RR >5) were detected. Resistance level was partially suppressed inmost of the strains when piperonyl butoxide (100 mu g/insect) and S,S,S,-tributylphosphorotrithioates (30 mu g/insect) were used, indicating possible involvement of elevated monooxygenase and esterase. In addition, altered acetylcholinesterase was alsosuspected in eight strains. The percentage mortality of field populations were found to be distributed at two extremes when treated topically with deltamethrin at LC_99 (0.056 mu g/insect), indicating higher numbers of homogenous susceptible and resistant strains, respectively in those populations tested. Results obtained using topical application (percentage mortality) and surface-contact exposure method (resistance ratio) were not well correlated (r~2 = 0.169, P=0.023).