Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae)

Authors: Weiler, Lina; Behle, Robert; Eller, Fred; Muturi, Ephantus; Rooney, Alejandro - Alex

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2022
Publication Date: 1/25/2022
Citation: Flor-Weiler, L.B., Behle, R.W., Eller, F.J., Muturi, E.J., Rooney, A.P. 2022. Repellency and toxicity of a CO2-derived cedarwood oil on hard tick species (Ixodidae). Experimental and Applied Acarology. 86:299-312. https://doi.org/10.1007/s10493-022-00692-0.
DOI: https://doi.org/10.1007/s10493-022-00692-0

Interpretive Summary: For years, chemical pesticides were heavily used to control ticks known to transmit diseases to humans and livestock. The negative impact of these pesticides on treated environments and the development of pesticide resistance in ticks has prompted exploration for alternative control strategies that are based on natural products and organisms rather than synthesized chemicals. In this research, we showed that oil extracted from cedar wood using pressurized CO2 (CWO) both repelled and killed unfed nymphs of four hard tick species relative to treatment dosages. CO2 extraction produces CWO with high levels of cedrol, reported as the most bioactive component of CWO. The effectiveness of natural CWO as documented in this study will aid in development of CWO as an eco-friendly repellent and/or acaricide to reduce the incidence of tick vectored diseases.

Technical Abstract: The repellency and toxicity of a CO2-derived cedarwood oil (CWO) was evaluated against actively questing unfed nymphs of four species of hard ticks; Amblyomma americanum (L.), Dermacentor variabilis (Say), Ixodes scapularis (Say), and Rhipicephalus sanguineus (Latrielle). Using a vertical climb bioassay for repellency, nymphs of these species avoided a CWO treated filter paper in proportional responses to treatment concentrations. At 60 minutes of exposure, Ixodes scapularis nymphs were most sensitive with 50% repellency concentration (RC50) of 19.8 µg cm-2, compared with RC50 of 30.8, 83.8, and 89.6 µg cm-2 for R. sanguineus, D. variabilis and A. americanum, respectively. Bioassays determined the lethal concentration for 50% (LC50) and 90% (LC90) mortality of nymphs exposed to CWO in treated vials after 24- and 48-hours exposure. After 24 hours exposure, the LC50 values were 1.25, 3.45 and 1.42 µg cm-2 and LC90 values were 2.39, 7.59, and 4.14 µg cm-2 for D. variabilis, I. scapularis and R. sanguineus, respectively, but had minimal effect on A. americanum. After 48 hours exposure, the LC50 values were 4.14, 0.78, 0.79 and 0.52 µg cm-2, and LC90 values of 8.06, 1.48, 1.54 and1.22 µg cm-2 for A. americanum, D. variabilis, I. scapularis and R. sanguineus, respectively. The repellency of CWO on tick species decreased with time. The repellency and toxicity bioassays demonstrated concentration dependent responses of tick nymphs to the oil, indicating the potential of the CO2-derived cedarwood oil be developed as an eco-friendly repellent and/or acaricide.