PEORIA, Ill. — Nootkatone, a component of essential oil in grapefruit peels and other sources, is used in many food, beverage and personal care products because of its clean, citrusy taste and smell. Now, nootkatone may have another use: repelling blacklegged deer ticks that spread Lyme disease.

U.S. Department of Agriculture (USDA) entomologist Bob Behle is investigating the possibility with Kirby Stafford, an entomologist at the Connecticut Agricultural Experiment Station in New Haven, Conn.

Stafford began researching nootkatone’s tick repellency in 2008 and sought Behle’s formulation expertise when it became apparent the essential oil lacked sufficient residual activity to kill the tick’s tiny nymph stage, which is more likely to transmit the Lyme disease bacterium than the larger, easier-to-spot adults.

In studies at the Crop Bioprotection Research Unit, operated in Peoria by the Agricultural Research Service (ARS), Behle and colleagues refined a spray-dry procedure that uses lignin to encapsulate the nootkatone. ARS is USDA’s principal scientific research agency.

In nature, lignin acts like a molecular mortar that binds plant cell walls. In this use, the lignin served as semipermeable packaging that extended nootkatone’s residual activity and improved its effectiveness.

In greenhouse tests, the lignin-encapsulated (LE) nootkatone lasted longer than a previously tried emulsified concentrate formulation and caused less harm to cabbage plants when applied at standard field rates. No signs of plant damage were observed when researchers applied the LE formulation in outdoor trials, conducted in 2009 on residential properties. Just as importantly, no live ticks were recovered from treated sites. Another round of tests was conducted this past June on nine residential properties — five of them using another nootkatone-encapsulating formulation devised by Behle.

In 2009, the U.S. Centers for Disease Control and Prevention reported close to 30,000 confirmed cases of Lyme disease, which can affect the joints, heart and nervous system of afflicted individuals if left untreated. — Jan Suszkiw, Agricultural Research magazine

Read more about the research in the January 2011 issue of Agricultural Research magazine by clicking here.