The Journal of

  Background: German cockroach, Blattella Germanica, is a mechanical vector of various pathogenic agents such as viruses, bacteria, protozoa and parasite eggs. The purpose of this study was to determine the susceptibility level of German cockroach to bendicarb and carbaryl from carbamate insecticides, and malathion and chlropyrifos from organophosphorous insecticides.

  Methods: In this study, after collecting wild German cockroach strains from several hospitals and dormitories in Tehran, they were transferred to Cockroach Insectarium and were reared under the same laboratory conditions. Then the susceptibility level of these wild strains were compared by discriminating dose of bendicarb, carbaryl, malathion and chlropyrifos insecticides which were estimated by susceptible strain via surface contact method.

  Results: Results from the effect of discriminating dose against wild German cockroach strains showed that the lowest and the highest concentration of discriminating dose was allocated to chlropyrifos (6.63 mg/m2) and carbaryl (390.11 mg/m2), respectively. Most wild strains showed a degree of resistance and tolerate to bendicarb, carbaryl, malathion and chlropyrifos insecticides.

  Conclusion: This study shows that the carbamate insecticides, especially carbaryl do not currently have efficiency against German cockroach, so application of these insecticides should be stopped as a recommendation. Due to their malathion resistance and possible cross-resistance among them, organophosphorous insecticides are also recommended not to be used.