Efficacy of carvacrol on Rhipicephalus (Boophilus) microplus engorged female ticks (Canestrini, 1887) (Acari: Ixodidae): effects on mortality and reproduction.

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%.

Acaricidal activity of essential oil of Syzygium aromaticum, hydrolate and eugenol formulated or free on larvae and engorged females of Rhipicephalus microplus.

The cattle tick, Rhipicephalus microplus (Canestrini, 1888) (Ixodida: Ixodidae), is the most important ectoparasite in cattle-breeding areas and is responsible for severe economic losses. Synthetic acaricides have been used to control this parasite. However, the need for safer products has stimulated the search for new acaricides, such as those to be obtained from medicinal plants. The essential oil of Syzygium aromaticum (clove) has many biological properties and shows great potential for use in veterinary applications. In the context of the need for new agents, this study investigated the in vitro properties of the hydrolate, essential oil and the main constituent of S. aromaticum, eugenol, in formulated and free applications against larvae and females of R. microplus. Eugenol and the essential oil caused 100% mortality in larvae at starting applications of 2.5 mg/mL and 5.0 mg/mL, respectively. The hydrolate showed no activity. Both eugenol and essential oil had good efficacy in adult immersion tests at 50 mg/mL and achieved 100% efficacy at a concentration of 100 mg/mL. The results of these tests reaffirm the important potential of clove essential oil and eugenol.