Chemical Composition and Acaricidal Activity of the Essential Oils of Some Plant Species of Lamiaceae and Myrtaceae against the Vector of Tropical Bovine Theileriosis: Hyalomma scupense (syn. Hyalomma detritum).

ABSTRACT

The present study aimed to investigate the acaricidal properties of six essential oils. They were extracted from some plant species (Lamiaceae and Myrtaceae) using the technique of hydrodistillation with the Clevenger apparatus. The chemical compositions of the essential oils under study were determined by gas chromatography-mass spectrometer (GC-MS). An Adult Immersion Test (AIT) and a Larval Immersion Test (LIT) were used to evaluate the acaricidal activity of these essential oils against the adults and larvae of Hyalomma scupense. GC-MS analysis showed the major constituents of each essential oil 25.49% of α-thujone (lavender); 46.82% of carvacrol (oregano); 78.78% of carvacrol (thyme); 40.27% of 1,8-cineole (blue gum); 17.45% of p-cymene (river red gum); and 26.96% of 1,8-cineole (rosemary). The biotests on the essential oils revealed that they inhibit the reproduction of H. scupense engorged females at a rate of 100 % with doses of 0.781 µl/ml of rosemary, 1.562 µl/ml of thyme, 3.125 µl/ml of lavender and oregano, and 6.250 µl/ml of blue gum and river red gum. After a treatment that lasted for 24 hours, essential oils showed a larvicidal activity with respective values of lethal concentrations (LC) LC50, LC90, and LC95 (0.058, 0.358, and 0.600 µl/ml for thyme; 0.108, 0.495, and 0.761 µl/ml for rosemary; 0.131, 0.982, and 1.740 µl/ml for oregano; 0.155, 2.387, and 5.183 µl/ml for blue gum; 0.207, 1.653, and 2.978 µl/ml for river red gum; and 0.253, 2.212, and 4.092 µl/ml for lavender). This is the first report on the acaricidal activity of these essential oils against H. scupense. The results obtained showed that the essential oils with chemotype carvacrol, 1,8-cineole, α-thujone, and p-cymene are highly acaricidal, and they can be used for ticks control. However, further studies on their toxicity in nontarget organisms are required.