Comparative Susceptibility of North American Bluttellu (Orthoptera: Blattellidae) Species to Insecticides

Abstract

Toxicities of six insecticides to susceptible and resistant German cockroach, Blattella germanica (L.), Asian cockroach, B. asahinai Mizukubo, and field cockroach, B. vaga Hebard were determined. Toxicity by chemical class was pyrethroid > carbamate = organophosphorus for each species. In surface contact and topical application ( µ g/insect) bioassays. the susceptible German cockroach strain was more tolerant than the Asian cockroach to diazinon, propoxur, fenvalerate, and cypermethrin. Both species were equally susceptible to bendiocarb residues and to chlorpyrifos that was applied topically. The Asian cockroach was more susceptible to all insecticides when LD50's were expressed as µ g/mg body weight. The susceptibility profile of the field cockroach was similar to that of the susceptible German cockroach strain except that the field cockroach was relatively tolerant of chlorpyrifos. High organophosphorus resistance (>14-fold in topical application tests) was observed in the resistant German cockroach strain; however, the degree of resistance was lower when estimated by the contact toxicity test. We conclude that insecticides that are used for control of the German cockroach will also control the Asian cockroach. Our data suggest that topical application assays are the most sensitive method for monitoring resistance in the German and Asian cockroach.