Insecticide susceptibility of horn flies, Haematobia irritans (Diptera: Muscidae), in the State of Mato Grosso do Sul, Brazil.

• Autor(a) principal: BARROS, A. T. M.
• Data de Publicação: 2007
• Outros Autores: GOMES, A., KOLLER, W. W.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da EMBRAPA (Repository Open Access to Scientific Information from EMBRAPA - Alice)
• Texto Completo: http://www.alice.cnptia.embrapa.br/alice/handle/doc/326335
• topic: Mosca-do-chifre; Piretróide; Mato Grosso do Sul; Brasil; Horn flies; Pyrethroid; Organophosphate; Haematobia Irritans; Resistência a Pesticida; Sanidade Animal; animal health; Brazil; pesticide resistance

Horn flies from wild populations were collected on cattle and exposed to filter papers impregnated with cypermethrin, permethrin, or diazinon and mortality was assessed after two hours. Resistance to cypermethrin was detected in all populations, with resistance ratios (RR) ranging from 27.6 to 91.3-fold. Permethrin bioassays provided apparently low levels of resistance (RR<5), however, resistant flies were found in 96.9% of the populations based on diagnostic concentrations. From both pyrethroid bioassays, resistance was detected in 97.4% of the populations. On the other hand, a high susceptibility to diazinon (RR d 1.1) was detected in all populations. Pyrethroid products, most cypermethrin (92.3%) and deltamethrin (66.7%), were used in all ranches controlling horn flies (97.5%). Insecticide treatments, usually incorrectly applied, were routinely delivered by manual backpack sprayers in most ranches (84.5%). This profile of insecticide use helps to explain the widespread resistance of horn flies to pyrethroids in the state as well as their high susceptibility to the organophosphate. Inadequate control practices contribute to aggravate the resistance problem and its consequences.