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Susceptibility to diazinon in populations of the horn fly, Haematobia irritans (Diptera: Muscidae), in Central Brazil

2002; Instituto Oswaldo Cruz, Ministério da Saúde; Volume: 97; Issue: 6 Linguagem: Inglês

10.1590/s0074-02762002000600029

1678-8060

Antônio Thadeu Medeiros de Barros, Alberto Gomes, Ana Paula K Ismael, W. W. Koller,

Insect Pest Control Strategies

From October 2000 to April 2001, insecticide bioassays were conducted in 18 ranches from 10 counties in the states of Mato Grosso and Mato Grosso do Sul, in Central Brazil. Horn flies from wild populations were exposed to diazinon-impregnated filter papers immediately after collection on cattle, and mortality was recorded after 2 h. A high susceptibility to diazinon was observed in all tested populations. The LC50s ranged from 0.15 to 0.64 µg/cm², and resistance ratios were always lower than one (ranging 0.1-0.6). Pyrethroid products, most applied by backpack sprayers, have been used since the horn fly entered the region, about 10 years ago. The high susceptibility observed to diazinon indicates that this insecticide (as probably other organophosphate insecticides) represents an useful tool for horn fly control and resistance management, particularly in pyrethroid-resistant populations.