Aphid alarm pheromone: An overview of current knowledge on biosynthesis and functions

Aphids are important agricultural and forest pests that exhibit complex behaviors elicited by pheromonal signals. The aphid alarm pheromone – of which (E)-β-farnesene is the key (or only) component in most species – plays important roles in mediating interactions among individuals as well as multitrophic interactions among plants, aphids, and aphid natural enemies. Though many important questions remain to be answered, a large body of research has addressed various aspects of the biology, physiology, and ecology of aphid alarm pheromones. Here we review recent advances in our understanding of (a) the identity and composition of aphid alarm signals; (b) their biosynthesis and production; (c) their effects on conspecifics; (d) their role as cues for other insect species; and (e) their potential application for the management of pest organisms.

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► In response to a danger, aphids secrete alarm pheromones.
► Three metabolites have been shown to have aphid alarm pheromone activity: (E)-β-farnesene, germacrene A, and α-pinene.
► Mechanisms of production and regulation of these compounds are not fully characterized but major advances have been made.
► Aphid alarm pheromones mediate ecological interactions among aphids, and between aphids and other organisms.
► The chemical ecology of aphid alarm signaling has significant applied relevance.