We report here that the aphid Myzus persicae (Sulzer) is repelled, at a distance of 1-3 mm, from leaves of the wild potato Solatium berthaultii Hawkes. In addition, air from above the foliage induces rapid dispersal of settled aphid colonies, behaviour similar to that of aphids exposed to the aphid alarm pheromone, (E)-β-farnesene1-4. The presence of substantial quantities of (E)-β-farnesene in air around S. berthaultii foliage and in ethanolic washings from it was demonstrated by gas chromatography (GC) and mass spectrometry (MS); the (E)-β-farnesene is probably released from glandular hairs on the foliage. We believe that this represents the first time, and certainly for a species related to a major food crop, that a plant has been shown to use the aphid alarm pheromone as an allomone. If this ability could be introduced into cultivated potatoes, it might provide some protection against aphids and hence aphid-borne viruses.