Chemical Composition and In Vitro Acaricidal Activity of Schinus terebinthifolius Essential Oils from Leaves and Fruits Against Rhipicephalus microplus

Resistance of ticks to synthetic acaricides has reduced the effectiveness of commercial products and increased interest in sustainable alternatives such as essential oils (EOs). This study characterized the chemical composition of EOs obtained from leaves and fruits of Schinus terebinthifolius, evaluated the in vitro acaricidal activity of EOs against R. microplus, and assessed its susceptibility to conventional acaricides. Ticks were collected from naturally infested cattle that had not been subjected to acaricidal treatment. EOs were obtained by hydrodistillation and characterized by gas chromatography–mass spectrometry. Adult immersion tests were performed in triplicate using seven combinations of synthetic acaricides, EOs at concentrations of 1%, 0.5%, and 0.25%, and control groups. The leaves and fruit EOs contained 48 and 20 compounds, respectively. Among the commercial acaricides, only two formulations achieved efficacy higher than 95%. The EOs exhibited concentration-dependent activity. At 1%, adult female mortality was 16.67% and 20.0% for leaf and fruit EOs, respectively, while the corresponding acaricidal efficacies were 96.69% and 97.90%. EO concentration showed positive and negative linear associations with oviposition inhibition and reproductive parameters, respectively. These findings indicate that the EOs of S. terebinthifolius exhibit in vitro acaricidal activity against R. microplus, supporting further investigation of their potential for tick control.