The essential oil of Hemizygia petiolata Ashby (Lamiaceae) contains high levels (>70%) of the
sesquiterpene (E)-β-farnesene, the alarm pheromone for many economically important aphid species. In
order to test the suitability of H. petiolata oil as a source of (E)-β-farnesene for use in new integrated
aphid control strategies, behavioural responses of pest aphid species were studied in laboratory and field
experiments. In alarm pheromone assays the peach-potato aphid, Myzus persicae Sulzer, and the pea
aphid, Acyrthosiphon pisum (Harr), showed a lower level of response to the oil than expected given the
high levels of (E)-β-farnesene. It was shown thatminor components in the oil, (+)-bicyclogermacrene and
(−)-germacrene D, caused inhibition of the alarm response for M. persicae and A. pisum respectively.
Nevertheless, in olfactometer studies the oil was directly repellent to A. pisum and the grain aphid,
Sitobion avenae F. Sitobion avenae was not only repelled by (E)-β-farnesene but also by (−)-germacrene
D. Furthermore, although it was not directly repellent to M. persicae, the oil interfered with its attraction
to host plant stimuli. In field plot experiments, numbers of A. pisum were significantly reduced in plots
treated with a slow release formulation of the oil, when compared with control plots.
2005 Society of Chemical Industry