Carbamate Insecticides Resistance Monitoring of Adult Male German Cockroaches, Blattella germanica (L.), in Southern Iran

Background: the german cockroach, blattella germanical. (dictyoptera: blattellidae), has become resistant to manyinsecticides due to control failures in hospital and studentdormitory settings of southern iran.objective: this study was thus designed to detect and monitorcarbamate resistance in two strains of german cockroach usinglethal dose bioassay methods.methods: wild dormitory (d) and hospital (h) strains werecollected. adult males were subjected to the jar exposureprocedure. a range of concentrations based on the world healthorganization (who) standard concentration of carbamateinsecticides (carbaryl, bendiocarb, propoxur) were used. foreach insecticide, four to seven different concentrations leadingto > 0% and < 100% mortality were assayed. ten insects wereplaced in each jar and the exposure time of contact was heldconstant for 30 minutes. mortality data (as ld50) were assessedusing probit analysis.results: although both strains showed lethality values abovethose of the who standards, the h strain was more resistant toall of the three carbamate insecticides than the d strain, possiblydue to the frequent and excessive dosage of these chemicals usedin the hospital environment. the order of resistance for h strainwas carbaryl > propoxur > bendiocarb. the ratio of ld50 in hstrain to that of d strain for bendiocarb was about twice that ofthe other two insecticides indicating that german cockroacheswere most susceptible to bendiocarb under both environments.conclusion: it is concluded that excessive reliance on carbarylin both d and h settings has led to resistance.