Identification of the Alarm Pheromone of Cowpea Aphid, and Comparison With Two Other Aphididae Species

In response to a predator attack, many Aphidinae species release an alarm pheromone, which induces dispersal
behavior in other individuals within the colony. The major component of this pheromone is the sesquiterpene (E)-
β-farnesene (Eβf), but variations occur between aphid species. In the present work, we collected, identified, and
quantified the alarm pheromone of Aphis craccivora Koch (Hemiptera: Aphididae), before quantifying the escape
behavior induced in the neighboring individuals. We compared the semiochemistry and associated behavior of alarm
signaling with two other aphid species: Myzus persicae (Sulzer) (Hemiptera: Aphididae) and Aphis fabae Scopoli
(Hemiptera: Aphididae). Eβf was the only volatile found for each species. M. persicae produces a higher quantity of
Eβf (8.39 ± 1.19 ng per individual) than A. craccivora (6.02 ± 0.82 ng per individual) and A. fabae (2.04 ± 0.33 ng per
individual). Following exposure to natural doses of synthetic Eβf (50 ng and 500 ng), A. craccivora respond more
strongly than the two other Aphidinae species with 78% of the individuals initiated alarm behavior for 500 ng of Eβf.