Abstract
ABSTRACT. Nascimento C.G., Grisi L., Fazio-Junior P.I., Lambert M.M., Coelho C.N., Magalhães V.S., Coumendouros K. & Scott F.B. [Monitoring resistance of Haematobia irritans (Linnaeus, 1758) (Diptera: Muscidae) to insecticides in the Northwest State of São Paulo]. Monitoramento da resistência de Haematobia irritans (Linnaeus, 1758) (Diptera: Muscidae) a inseticidas no noroeste do estado de São Paulo. Revista Brasileira de Medicina Veterinária, 34(Supl. 1):21-27, 2012. Convolution - Divisão de Antiparasitários, Avenida Norma Valério Correa, 571 casa 97, Bairro Jardim Botânico, Ribeirão Preto, SP 14021-593, Brasil. E-mail: cristiano.grisi@convolution.com.br The objective of the present study was to monitor the resistance of populations of Haematobia irritans insecticide tests were carried out on properties in the northwest region of São Paulo, using filter paper impregnated with insecticides in Petri dishes. The pyrethroids cypermethrin and permethrin and organophosphate diazinon were tested in different concentrations. For each dilution three replicates were used, with at least twenty flies each of the horns. The readings of the plates were made with two and four hours of exposure, calculating the lethal concentration 50 (LC50) and the resistance factor (RF) for each population. Populations of H. irritans northwestern state of São Paulo can be considered highly susceptible to cypermethrin and resistant to permethrin and diazinon. The results found in three farms in the northwestern state of São Paulo were compared with data recorded thirteen years ago by researchers at the Federal Rural University of Rio de Janeiro, in the same region, during the initial dispersal of H. irritans. In vitro tests proved to be an important tool in the indication of populations of H. irritans resistant to insecticides.