Effect of nootkatone on the in vitro mortality of the ticks Rhipicephalus microplus and Amblyomma sculptum (Acari: Ixodidae)

ABSTRACT In Brazil, two tick species are mainly involved in public health and livestock issues: Amblyomma sculptum and Rhipicephalus microplus, respectively. Nootkatone, a sesquiterpenoid isolated from Chamaecyparis nootkatensis, has been described in the literature as an environmentally friendly alternative method of control, with repellent and toxic action against different insect and tick species from the Northern Hemisphere. The objective of the present study was to evaluate the effect of nootkatone on the in vitro mortality of R. microplus and A. sculptum. Different dilutions of nootkatone (0.5, 1, 2, 5 and 10%) were used on instars of both tick species. In A. sculptum engorged larvae, unfed nymphs, and unfed adults, 2% nootkatone resulted in 95% mortality in almost all tests. An in vitro mortality rate of 95% was observed for larvae and engorged females of R. microplus with 1% and 0.5% nootkatone, respectively. Additionally, 5% and 10% nootkatone were at least 97% effective against engorged larvae, unfed nymphs, and unfed adults of A. sculptum and larvae and engorged females of R. microplus. This was the first study to use nootkatone against ticks from Brazil and the data suggest that nootkatone has great potential as a tool for tick control.