The susceptibility values for field-collected (BG-BG) and laboratory (KS-BG) strains of German cockroaches, Blattella germanica (L.) to 5 synthetic pyrethroids and 3 organophosphates were assessed by topical application. Both KS-BG and BS-BG demonstrated the highest levels of susceptibility to deltamethrin. The KS-BG demonstrated the lowest susceptibility level to fenthion, while the BS-BG field population showed the lowest susceptibility to bifenthrin. The BS-BG field population showed resistance levels of 50 to 640 fold higher against the eight pesticides evaluated compared to the KS-BG. The resistance ratios (RR) of the eight pesticides were compared using populations of B. germanica that were collected from the same locality during 2007 and 2014. The field population of B. germanica collected during 2014 demonstrated significantly high resistance to an organophosphate and all pyrethroids when compared with those collected during 2007, but RR values were < 10 except for chlorpyrifos-methyl and chlorpyrifos with RR values of 74 and 104, respectively.

• Gi-Hun Kim(Division of Medical Entomology, Center for Immunology and Pathology, NRIH, KCDC)
• Chang won Jang(Division of Medical Entomology, Center for Immunology and Pathology, NRIH, KCDC)
• Young-Ran Ju(Division of Medical Entomology, Center for Immunology and Pathology, NRIH, KCDC)
• Kyu-Sik Chang(Division of Medical Entomology, Center for Immunology and Pathology, NRIH, KCDC)