Persistence Enhancement of a Promising Tick Repellent, Benzyl Isothiocyanate, by Yeast Microcarriers.

Phenethyl isothiocyanate isolated from root oil and its derivatives were tested at different doses in a bioassay designed to evaluate repellency against individual nymphs. Among the tested compounds, benzyl isothiocyanate exhibited repellency against nymphs at the lowest dose of 0.00625 mg/cm, followed by phenethyl isothiocyanate (0.0125 mg/cm) and phenyl isothiocyanate (0.025 mg/cm). The behavioral responses of nymphs exposed to benzyl isothiocyanate and phenethyl isothiocyanate indicated that the mode of action of these compounds can be mainly attributed to the vapor phase. Encapsulated benzyl isothiocyanate showed repellency up to 120 min post-application at 0.1 mg/cm, whereas pure benzyl isothiocyanate showed repellency up to 60 min post-application at 0.1 mg/cm. The present study suggests that benzyl isothiocyanate is a potential repellent for protection against nymphs, and encapsulation in yeast cells may enhance the repellency effect.