Assessment of resistance to permethrin of german cockroaches (Blattella germanica L.) caught in Poland

: Resistance to permethrin was tested in cockroaches caught in health service institutions in various parts of Poland. The tests were carried out by the contact method as recommended by the WHO. The density of the insecticide was 20 mg/m2. The experiment was done only on male insects, calculating the values of LT50 and LT90 in insect groups caught in various localities. These values were compared with LT50 and LT90 values in sensitive insects exposed to the insecticide, and the resistance indices R50 and R90 were calculated. This made possible determination of permethrin resistance of the populations from various areas. The results showed that the sensitivity of the insects varied. Cockroaches caught in Opole, Biala Podlaska, Szczecin, Warsaw were highly resistant to permethrin, while those from Plock, Piotrkow Trybunalski, Chojnow, Nowy Sacz tolerated the insecticide, and those from Jedrzejow were as sensitive as control laboratory insects.