INSECTICIDE RESISTANCE AND SYNERGISM IN-FIELD COLLECTED GERMAN COCKROACHES (DICTYOPTERA, BLATTELLIDAE) IN PENINSULAR MALAYSIA

Twelve strains of German cockroach, Blattella germanica (Linnaeus) wer e collected from various locations in Peninsular Malaysia and tested f or their susceptibility to three groups of insecticides applied topica lly. The levels of resistance were low to high (2.8 to 92x) for carbam ates (propoxur and bendiocarb), low (2.0 to 7.6x) for organophosphate (chlorpyrifos) and low to moderate (1.0 to 23x) for pyrethroids (cyper methrin and permethrin) when compared to a susceptible strain. Five st rains, resistant to both cypermethrin and permethrin, were also resist ant to DDT, phenothrin and deltamethrin. Propoxur resistance in ten st rains was suppressed with the synergists, piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF(R)), suggesting monooxygenase and esterase involvement in the resistance. However, the levels of res istance for cypermethrin and permethrin were not affected when using e ither PBO or DEF(R).