Resumo

BRAVO, Maribel J; CORONADO, Alfredo  e  HENRIQUEZ, Humberto. Susceptibility to coumaphos on larvae and adult ticks Boophilus microplus in dairy farms from Lara state, Venezuela. Zootecnia Trop. [online]. 2008, vol.26, n.1, pp.41-46. ISSN 0798-7269.

The cattle tick Boophilus microplus is widely distributed in the world and causes significant economic losses. The aim of this work was to determine in vitro susceptibility of coumaphos ixodicide in adult ticks using five different concentrations including the manufacturer’s recommended dosage, and the larvae mortality using therapeutic dose. A sample of 240 engorged females was collected from four dairy farms in Lara state, (60 ticks/farm), divided in groups of 10 ticks averaging 220 mg/tick. Commercial coumaphos formulation (20%) was used to prepare the working concentrations of 125, 250, 500, 1000 and 2000 ppm for the adults immersion test (AIT), and the control group was submerged in water. The Shaw larvae immersion test was applied in larvae obtained of this ticks population. In farm 1, weight average of the total egg masses was significantly smaller in the groups treated with coumaphos at concentrations of 1000 and 2000 ppm with respect to control group. Differences were not observed between the groups treated at the concentrations of 125, 250, 500, 1000 and 2000 ppm in each of the four farms. Statistical differences not were observed in the efficacy among groups. Higher concentrations of coumaphos did not increase the efficacy of the product. The adult ticks of B. microplus were resistant to coumaphos. Mortality in larvae reached 100%.

Palavras-chave : Boophilus microplus; coumaphos; efficacy; larvae; adult ticks.

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