Acaricidal Effect of Essential Oils in the Control of Rhipicephalus microplus and Amblyomma mixtum Larvae in Mexico

The objective of this study was to evaluate essential oils (EOs) as an alternative control method for Rhipicephalus microplus and Amblyomma mixtum larvae. The EOs used were obtained by steam distillation from the leaves of cinnamon (Cinnamomum verum), mexican mint (Plectranthus amboinicus), lemongrass (Cymbopogon citratus), peppercorns (Pimenta dioica), and peruvian pepper tree (Schinus molle). To evaluate the acaricidal effect of EOs against the larvae of two tick species, a larval immersion test (LIT) was performed using six concentrations (10 mg/mL, 5 mg/mL, 2.5 mg/mL, 1.87 mg/mL, 1.25 mg/mL, and 0.6 mg/mL), in addition to a negative control group (water + ethanol) and three positive controls (organophosphate, formamidine, and pyrethroid). LIT results were obtained 48 h after exposure. Data were processed using Probit procedure to determine the lethal concentrations at 50% (LC50), 95% (LC95), and 99% (LC99). For R. microplus, 99% mortality was obtained at concentrations as low as 1.4 mg/mL for S. molle, while the highest LC99 was recorded with P. dioica at 23 mg/mL. In the case of A. mixtum, higher concentrations were required to achieve a high mortality rate. EO of P. amboinicus had the lowest acaricidal effect, requiring 26.2 mg/mL to achieve an LC99, while S. molle required a concentration of 6.9 mg/mL to achieve an LC99.