Susceptibility of the Californiathrips,
Frankliniella occidentalis
(Pergande) to formetanate (Dicarzol 500 SP), methamidophos (Tamaron 600 SL), dimethoate (Perfekthion), and spinosad (Success 48) was evaluated using serial concentrations of insecticides sprayed on bean leaves with a PotterTower. In the bioassays, adult females collected in three localities of the V
th Region (Ocoa 32°55' S lat and 71°05' W long, 365 m.o.s.l.; Auco 32°52' S lat and 70°40' W long., 762 m.o.s.l., and Vichiculén 32°52' S lat and 70°57' W long, 279 m.o.s.l.) were used. The results were submitted to a Probit analysis, and the resistance factors (FR) were calculated with lethal concentrations 50 (LC
50) of the most sensible strain to the four insecticides. The FRs obtained forspinosadwere: 1, 1.3 and 1.5; to dimethoate 1, 1.6 and 7.4; to metamidophos 1, 1.5 and 4.2 and, to formetanate 1, 2 and 2, in Ocoa, Auco and Vichiculén, respectively. The Vichiculén strain had lowest susceptibility to all insecticides tested. For all strains, the response to spinosad showed the highest susceptibility. Recommendations to develop strategies to manage resistance of
F. occidentalis to insecticides are discussed.