Acaricidal activity of illicium verum, Laurus nobilis and Origanum vulgare essential oils against Rhipicephalus microplus (Acari: Ixodidae)

Abstract

Due to the increase of Rhipicephalus microplus populations resistant to synthetic acaricides, as well as the need for safer products to be used in cattle breeding, it becomes necessary to search for new products, such as those to be obtained from plants. Thus, this study aimed to determine the chemical composition and evaluate the acaricidal activity of Illicium verum, Laurus nobilis and Origanum vulgare essential oils against R. microplus in vitro. The essential oils were obtained by hydrodistillation, and chemical characterization was performed by gas chromatography coupled with mass spectrometry (GC-MS). The acaricidal activity of each essential oil was first evaluated on larvae at concentrations 2.5, 5.0, 10.0, 15.0 and 20.0 mg/mL. The results of the larval treatment indicated that only the essential oil of I. verum caused mortality. Thus, immersion tests of this oil were conducted on engorged females of R. microplus at concentrations of 10.0, 20.0, 40.0, and 60.0 mg/mL. GC-MS analysis of I. verum, L. nobilis and O. vulgare essential oils showed E-anethole (88.32%), 4-terpineol (24.92%) and 1.8-cineol (74.23%) as the major components, respectively. Regarding the acaricidal activity both in larvae and R. microplus engorged females, only I. verum essential oil showed effective, causing 99.8% of larvae mortality at concentration 15 mg/mL and achieved 84.9% efficacy on engorged females at concentration 60mg/mL. This study provides support for further investigation of I. verum essential oil components as novel natural products to R. microplus control.