Comparison of Lethal Effect of Carvacrol, Thymol, Permethrin and Cypermethrin Toxicants on German cockroaches (Blattella germanica)

German cockroaches are one of the most common indoor pests which could be effective in the transmission of viral, bacterial, and parasitic pathogens. Extensive use of pyrethroid pesticides resulted in resistance in the cockroaches. Studies have showed that bioactive herbal compounds can serve as alternative to chemical pesticides. Aim of the present study was to evaluate lethal effect of carvacrol, thymol, permethrin and cypermethrin on German cockroaches in vitro. In this study, toxic effects of carvacrol, thymol, permethrin and cypermethrin by contact and fumigation tests in dilutions of 0.125, 0.25, 0.5 and 1 µg/cm3 were tested. After 24 h treatment in the contact toxicity test, thymol at all tested doses led to significant lethal effects in comparison to the control (p= 0.004). Thymol at all tested dilutions resulted in significant fumigation toxicity in comparison to the control (p= 0.001). In the present study, thymol in comparison to all other tested compounds exhibited more lethal activity on the German cockroaches.