Field Test for Repellency of Cedarwood Oil and Cedrol to Little Fire Ants

Abstract

Eastern redcedars (Juniperus virginiana L.) are an abundant renew- able resource and represent a potential source of valuable natural products that may serve as natural biocides. The aromatic wood can be extracted to obtain cedarwood oil (CWO) and critical carbon dioxide (CO2) extraction of eastern redcedars gives both high yields and high quality CWO. In this study, CO2-derived CWO and cedrol, the most abundant component of CWO, were field-tested for repellency against the little fire ant (LFA), Wasmannia auropunctata Roger, in a Hawaiian macadamia orchard. Field tests were conducted using chopsticks baited with peanut-butter placed in established LFA trails on macadamia tree trunks and branches. The chopsticks and any ants present were collected after ca. 24 hours and the number of ants determined by visual counting. Four treatments were compared: Hexane only control; mineral oil; CWO; and cedrol. Control chopsticks and chopsticks treated with mineral oil had very high numbers of ants and were statistically equivalent. The CWO-treated chopsticks had significantly fewer LFAs than all the other treatments. Chopsticks treated with cedrol had fewer ants than the control chopsticks but more than the chopsticks treated with CWO. This research suggests that CWO extracts from J. virginianna may provide a renewable source of a natural ant repellent and could help manage this invasive pest.