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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 97, No. 6, 2002, pp. 905-907
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Bioline Code: oc02174
Full paper language: English
Document type: Research Article
Document available free of charge
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Memórias do Instituto Oswaldo Cruz, Vol. 97, No. 6, 2002, pp. 905-907
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Susceptibility to Diazinon in Populations of the Horn Fly, Haematobia irritans (Diptera: Muscidae), in Central Brazil
Antonio Thadeu M Barros; Alberto Gomes; Ana Paula K Ismael & Wilson W Koller
Abstract
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 LC
50
s ranged from 0.15 to 0.64 µg/cm
2, 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.
Keywords
horn flies - insecticide - organophosphate - resistance - Centtral Brazil
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