Acaricidal activity of various essential oil components against acaricide-resistant Rhipicephalus microplus (Acari: Ixodidae)

Abstract

Rhipicephalus microplus, an important ixodid tick species, poses significant economic and health challenges to the livestock directly by impairing animal productivity and serving as a vector for various pathogens. Although tick control strategies broadly integrate synthetic acaricides and environmental management, the emergence of acaricide resistance undermines these efforts thereby, necessitating alternative approaches. This study evaluated the acaricidal efficacy of six essential oil components (EOCs) such as cedrol, cinnamaldehyde, citral, eugenol, limonene and menthol against deltamethrin and ivermectin resistant R. microplus population by larval packet test. Among the studied EOCs, cinnamaldehyde exhibited the highest acaricide potential (LC₅₀ = 0.042 %), followed by menthol (LC₅₀ = 0.084 %), eugenol (LC₅₀ = 0.171 %) and citral (LC₅₀ = 0.185 %). Cedrol (LC₅₀ = 1.09 %) demonstrated a lower activity, while limonene (LC₅₀ = 22.0 %) was least effective. Probit regression analysis revealed steep dose-response slopes for cinnamaldehyde, citral and eugenol indicating strong acaricidal effects at low concentrations. These findings identify cinnamaldehyde, menthol, eugenol and citral as promising candidates for the development of plant-based acaricides, supporting their potential integration into the sustainable tick management strategies for management of acaricide-resistant R. microplus populations.