Tick repellent activities of supercritical fluid extract from Chamaecyparis obtusa against Haemaphysalis longicornis

Supercritical fluid extraction (SFE) is a rapid, selective, and convenient method for sample preparation prior to the analysis of compounds in a volatile product of plant matrices. In this study, insecticidal activity and repellency were examined in a laboratory study to determine the active constituent of Chamaeparis obtusa and a supercritical fluid extract from Chamaeparis obtusa against hard tick Haemaphysalis longicornis. The repellency of C. obtusa oil was evaluated in comparison with two commercial repellents (Icaridin and DEET) against H. longicornis. Filter-paper diffusion assay revealed that C. obtusa oil (3.2 µg/cm 2 ) had a 100 % repellency and icaridine (3.2 µg/cm 2 ) had a 96.1 % repellency at 120 min. Repellencies of 31 compounds against H. longicornis were compared with the repellency of DEET at 3.2 µg/cm 2. Responses varied according to the test compound and exposure time. Repellencies of α-terpinene, terpinene-4-ol, and α-terpineol were 100 % at 30 min post-treatment. They were 85.5 %, 56.4 %, and 68.9 %, respectively, at 120 min. C. obtusa oil, α -terpinene, terpinene-4-ol, and α -terpineol merit further study as potential fumigants or lead compounds for the control of H. longicornis.