RESUMEN
The activity of carvacrol was evaluated in R. microplus female ticks by estimating the mean lethal concentration (LC50) and the acaricidal efficacy. Ticks were subjected to the Adult Immersion Test (AIT) to calculate LC50. From this value, the AIT was performed again at the concentrations of 20%, 40%, 60%, 80% and 100% of the LC50. Two control groups were established: one treated with distilled water and one with the solvent (ethanol 50%). The following parameters were evaluated: female weight before oviposition, egg mass weight, pre-oviposition and incubation period, hatching percentage, egg production index, fecundity rate, estimated reproduction, reduction in oviposition and hatching, and product efficacy. The obtained LC50 was 20.11 mg/mL. Egg mass weight, egg production index, pre-oviposition and fecundity rates of groups treated with 80% and 100% of LC50 were statistically different when compared to control groups. The product efficacy in groups treated with 100% of LC50 was 61.10%.