ABSTRACT
This work aimed to evaluate the susceptibility of Blattella germanica (Linnaeus, 1767) (L.) populations to deltamethrin and chlorpyrifos, and also to a recently registered insecticide fipronil. For this purpose, topical and tarsal contact bioassays were contrasted. Topical contact bioassay gave better discrimination between the susceptible strain and field-collected populations of B. germanica. For deltamethrin, the resistance ratios (RR) were 10.32; 14.08 and 100.80-fold with topical bioassay and 2.21; 2.25 and 1.98-fold with tarsal contact for RJ-1, RJ-2 and SP-1 populations, respectively. For chlorpyrifos, the RR were 4.98; 6.62 and 30.06-fold with topical bioassay and 1.35; 1.47 and 1.70-fold with tarsal contact, respectively. Results from a survey of B. germanica susceptibility to insecticides revealed the presence of genetic variability that confers resistance to deltamethrin, chlorpyrifos and fipronil in field-collected populations of B. germanica from the states of São Paulo and Rio de Janeiro. The RR varied from 10.32 to 100.80-fold for deltamethrin, 4.98 to 30.06-fold for chlorpyrifos and 2.00 to 6.36-fold for fipronil.
KEY WORDS:
German cockroach; bioassay; chlorpyrifos; deltamethrin; fipronil.