In vitro evaluation of essential oils derived from Piper nigrum (Piperaceae) and Citrus limonum (Rutaceae) against the tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)
The present research aimed to study the chemical composition and acaricidal activity of Citrus limonum and Piper nigrum essential oils against the cattle tick Rhipicephalus microplus. GC-MS analysis of C. limonum essential oil showed limonene (50.3%), -pinene (14.4%), and -terpinene (11.7%) as the major components; P. nigrum oil was mainly composed of -caryophyllene (26.2%), - ocymene (5.8%), and -pinene (5.5%).Acaricide activity was evaluated at concentrations of 2.5, 5.0, and 10.0% (v/v) of each plant oil, as well as 1 : 1 combination of both oils (5%: 5%, 2.5%: 2.5%, and 1.25%: 1.25%each), by immersing engorged R.microplus females for oneminute.The LC90 of oils from C. limonum, P. nigrum, and the combinationwere 4.9%, 14.8%, and 5.1%, respectively. C. limonum essential oil caused 100% mortality of engorged females at the highest concentration (10%). P. nigrum essential oil inhibited egglaying by up to 96% in a concentration-dependentmanner, suggesting it reduces tick fecundity.When combined, the oils presented toxicity as to C. limonumoil alone, but with stronger inhibition of oviposition (5% : 5%), indicating a possible additive effect against R.microplus.The present data provide support for further investigation of novel natural products to control bovine tick infestations
