ARS | Publication request: Efficacy and environmental persistence of nootkatone for the control of the blacklegged tick, Ixodes scapularis (Acari: Ixodidae) in the residential landscape

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 25, 2012
Publication Date: September 1, 2012
Citation: Bharadwaj, A., Stafford III, K.C., Behle, R.W. 2012. Efficacy and environmental persistence of nootkatone for the control of the blacklegged tick (Acari: Ixodidae) in residential landscapes. Entomological Society of America. 49(5):1035-1044.

Interpretive Summary: Homeowners recognize the threat posed by disease-transmitting ticks infesting their yards, but are reluctant to spray chemical pesticides for control. We demonstrated the potential of nootkatone, a plant-derived compound, to control ticks around homes in the Lyme disease endemic area of Connecticut. Formulations that encapsulated the oil provided the best control of ticks when tested by field applications. These results demonstrate that ticks can be controlled using more natural compounds with less potential hazard to homeowners and the environment, and generally support the development of safer pest control technologies.

Technical Abstract: We evaluated the ability of the plant-derived compound nootkatone to control nymphs of the blacklegged tick, Ixodes scapularis Say, applied to the perimeter of lawns around homes in Lyme disease endemic areas of Connecticut. Three formulations of nootkatone ranging from 0.05 to 0.84% (0.06 to 1.03 g ai/m^2^) were applied by a hydraulic sprayer from 2008-2010. The 0.84% emulsifiable concentrate nootkatone formulation provided 100% control of I. scapularis for a few days after application, but control declined to only 21% by 3 wk posttreatment. A combination of 0.05% nootkatone and, an entomopathogenic fungus, Metarhizium brunneum Petch. F52, resulted in 67 and 50% control for the 1st and 2nd wk posttreatment, respectively. The 0.84% emulsifiable nootkatone formulation was phytotoxic, although no damage was observed with the 0.05% formulation. A 0.56% (0.53 g AI/m^2^) lignin-encapsulated nootkatone formulation was applied in 2009, which provided 100% control of I. scapularis for 8 wk. In 2010, a lignin-encapsulated nootkatone (0.74 g AI/m^2^) and a Maillard-reaction encapsulated nootkatone formulation (0.96 g AI/m^2^) provided 80 and 62% tick control, respectively, at ~ 1 wk posttreatment, which declined to 40 and 27% by 3 wk posttreatment, but the difference in tick abundance was not significant (P = 0.05). No phytotoxicity was observed with the encapsulated formulations. Residual analysis of filter paper disks following the nootkatone application showed that 95% or more of the emulsifiable nootkatone was lost within 7 d in 2008. While a similar pattern of loss from filter paper samples was observed with the encapsulated formulations, nootkatone was more persistent in the leaf litter column with 10.3% remaining 7 d post application and some material was recovered up to 70 d posttreatment. Encapsulating nootkatone reduced environmental loss and phytotoxicity, and provided extended control of I. scapularis. While nootkatone can provide effective tick control and is a potential alternative to synthetic acaricides, further work is needed to refine formulations that avoid phytotoxicity and provide effective tick control.