Further studies on cross-resistance in the German cockroach.

Four strains of German cockroaches have been exposed to a variety of insecticides in an effort to obtain more information on the cross-resistance phenomenon in this species. The insecticides chlordane, aldrin, and lindane were each tested against chlordane-resistant, lindane-resistant, and non-resistant strains. The insecticides diazinon and Sevin were each tested against DDT-resistant, chlordane-resistant, and non-resistant strains. Adult females were used exclusively in these tests. The data are presented in the form of regression lines.The results show that the DDT-resistant strain is highly resistant to Sevin but is susceptible to diazinon, while the chlordane-resistant strain is susceptible to both of these compounds. Furthermore, the chlordane- and the lindane-resistant strains are both highly resistant to chlordane and to aldrin, but show only low-level resistance to lindane.The over-all picture of cross-resistance between insecticidal groups in the German cockroach is still one of relative simplicity. At the present time the only real exception is that reported in this paper: the DDT-resistant strain was found to be resistant to the carbamate insecticide Sevin.