The objectives of this study were to characterize the resistance of Blattella germanica (L.) to deltamethrin and chlorpyrifos and to evaluate their cross-resistance relationships to fipronil. The isolation of resistance was done under laboratory conditions from field-collected populations. Three cycles of selection pressure with deltamethrin and chlorpyrifos were conducted to obtain the Deltamethrin-R and Chlorpyrifos-R strains. The estimated LD50 for the susceptible (SUS) strain was 0.24 (IC 95% 0.18 - 0.31) and for Deltamethrin-R strain was 10.26 (IC 95% 7.28 - 14.17) mug deltametrina/mg. For chlorpyrifos, LD50 for the SUS strain was 4.16 (IC 95% 2.80 - 5.33) and for Chlorpyrifos-R strain was 24.98 (IC 95% 20.90 - 30.28) mug chlorpyrifos/mg. Therefore, the resistance ratios were approximately 43- and 6-fold to deltamethrin and chlorpyrifos, respectively. A low intensity of cross-resistance (approximately 2-fold) was observed between fipronil and the insecticides deltamethrin and chlorpyrifos. Thus, fipronil can be used as a good candidate in resistance management programs of B. germanica to deltamethrin and chlorpyrifos.
Insecta; German cockroach; urban pest; insecticide
