Title: Anointing chemicals and ectoparasites: responses by ticks and mosquitoes to Citrus (Rutaceae) peel exudates and monoterpene constituents Authors
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 8, 2011
Publication Date: April 18, 2011
Citation: Weldon, P., Carroll, J.F., Kramer, M.H., Bedoukian, R., Coleman, R., Bernier, U.R. 2011. Anointing chemicals and ectoparasites: responses by ticks and mosquitoes to Citrus (Rutaceae) peel exudates and monoterpene constituents. Journal of Chemical Ecology. 37(4):348-359. Interpretive Summary: Mosquito- and tick-borne diseases pose a threat to humans and domesticated animals. Plants are an important source of chemicals that protect against insect and tick bites. Because certain species of mammals and birds rub themselves with Citrus fruits (presumably for protection from harmful external parasites), we tested 24 chemicals that occur in Citrus species to ascertain their effects on mosquitoes (yellow fever mosquito) and ticks (lone star tick). Our behavioral tests showed that at least 10 Citrus compounds deterred the ticks and/or mosquitoes. Nine compounds impaired basic tick behaviors (e.g. climbing, righting themselves). Researchers studying chemical ecology and host/parasite behavior will be interested in these findings. Our results will provide valuable leads for manufacturers seeking to develop repellent products from natural sources.
Technical Abstract: Some birds and mammals rub their feathers or fur with the fruits or leaves of Citrus spp. or other Rutaceae, presumably to deter ectoparasites. We measured avoidance and other responses by the lone star tick (Amblyomma americanum) and the yellow fever mosquito (Aedes aegypti) to lemon peel exudate and to 24 monoterpenes (racemates and isomers), including hydrocarbons, alcohols, aldehydes, acetates, ketones, and oxides, present in citrus fruits and leaves in order to examine their potential as ectoparasite deterrents. Ticks allowed to crawl up a vertically suspended paper strip onto a chemically treated zone avoided the peel exudate and most highly avoided carveol, citronellol, geraniol, a-terpineol, citral, carvone, citronellyl acetate, and geranyl acetate. Ticks confined for 1 h in chemically treated paper packets were most impaired in climbing and other behaviors following exposure to the peel exudate and, of the compounds tested, to carveol. Mosquitoes confined in chambers with chemically treated feeding membranes landed and fed less, and flew more, when exposed to the peel exudate than to controls, and when exposed to aldehydes, oxides, or alcohols than to acetates or hydrocarbons. Mosquitoes in an olfactometer, however, were attracted to a lacerated lemon and some compounds. Our results support the hypothesis that anointing with citrus-derived chemicals deters ticks, but we suspend judgment on its value as a defense against mosquitoes. We suggest that some compounds may be converted into more potent ectoparasite deterrents when oxidized on the integument of anointed animals.