Ylang-ylang oil (YYO) from Cananga odorata (Lam.) Hook.f. & Thomson and star anise oil (SAO) from Illicium verum Hook.f. were tested at four concentrations 0.05, 0.1, 0.2, 0.4 µl/cm2. Mortality rates were obtained by counting dead nymphs at 30-min intervals during the first 5 h after the start of exposure and then at 24, 48 and 72 h. Mortality increased with increasing oil concentration and time of exposure. The two highest concentrations of YYO (0.2, 0.4 µl/cm2) gave maximum lethal concentrations (LC) of 50 and 95% mortality after 4.5 h exposure. Mortality of 95% was obtained after 24 h with the next highest dose (0.1 µl/cm2), whereas LC95 required 3 days with the lowest YYO (0.05 µl/cm2). The lethal effect time (LT) was correlated with the duration of exposure, with a significant effect at 0.4 μl YYO/cm2 after 3 h' (LT50 = 3.2 h, LT95 = 4.3 h). In contrast, only the highest concentration of SAO, 0.4 µl SAO/cm2, showed increasing mortality with time of exposure. This reached LT50 after 10 h and LT95 after 24 h. However, with the lower concentration (0.2 µl/cm2) 50% mortality was reached after 24 h and 100% at 72 h. At to the lowest concentration of SAO (0.1 µl/cm2), 67% mortality after 48 h. The study indicates that YYO and SAO exhibit strong acaricidal properties against nymphs of I. ricinus and suggest that both YYO and SAO should be evaluated as potentially useful in the control of ticks.
Keywords: Acaricide; Cananga odorata; Illicium verum; Ixodes ricinus.