Evaluation of tea tree oil for controlling Rhipicephalus microplus in dairy cows

•In vitro tests was verified that tea tree oil (TTO) at 5 and 10% had 100% of effectiveness in the controlling ticks.•In vitro tests, pure TTO when used in dairy cows infested by ticks, showed an acaricide effect.•The nanocapsules of TTO lightly interfered the reproduction of these parasites. Our research aimed to test the effects of Melaleuca alternifolia oil (pure and in nanocapsules) in the control of Rhipicephalus microplus in dairy cattle. For this purpose, the in vivo studies used 15 cows distributed in three different groups with the same number of animals. Five cows remained untreated (Group A), representing the control group; other five cows were sprayed with TTO (at 5%) in its pure form (Group B); and five cows were sprayed with nanocapsules of TTO (at 0.75%) (Group C). On days 1 and 4 post-treatments (PT), all cows had their ticks counted. On day 1 PT, two ticks from each cow were collected to evaluate the effect of the treatment on ticḱs reproduction (in vitro assays). The pure form of TTO caused a significant reduction (P0.05). Treatment with TTO in nanocapsules (Group C) interfered with R. microplus reproduction, leading to lower oviposition by female ticks and hatchability (34.5% of efficacy). On the other hand, TTO oil (Group B) did not interfere on ticḱs reproduction, i.e. showed higher hatchability than the control group. Therefore, it is possible to conclude that pure TTO has an acaricidal effect in dairy cows, in addition to an effect on ticḱs reproduction when used its nanocapsulated form.