Autoria: BARROS, A. T. M.; GOMES, A.; KOLLER, W. W.

Resumo: Horn fly susceptibility to insecticides was evaluated in the state of Mato Grosso do Sul, Brazil, from October 2000 to september 2002. Insecticide bioassays (n=57) were conducted in 38 ranches from 14 municipalities throughout the state. 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 concetrations. From both pyrethroid bioassays, resistance was detected in 97.4% of the populations. On the other hand, a high susceptibility to diazinon (RR<1.1) was detected in all populations. Pyrethroid products, most cypermethrin (92.3%) and deltamethrin (66.7%), were used in all ranches controlling forn 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.

Ano de publicação: 2007

Tipo de publicação: Artigo de periódico

Unidade: Embrapa Gado de Corte

Palavras-chave: Brasil, Brazil, Haematobia Irritans, Horn flies, Mato Grosso do Sul, Mosca-do-chifre, Piretróide, Pyrethroid, Resistência a Pesticida, Sanidade Animal, animal health, cypermethrin, insecticide resistance, organophosphate, pesticide resistance, pyrethroid resistance