Background/Question/Methods
Aphids have evolved strategies to survive even in the presence of natural enemies. When aphids get attacked by natural enemies they emit alarm pheromone which alerts colony members. They then show a typical behavior when perceiving the alarm pheromone like waving with the antennae, kicking, walking, and dropping off the host plant. It is also known that the perception of alarm pheromone can induce production of winged offspring which then can leave the host plant. In most tested aphid species (E)-β-farnesene is the main, sometimes only, component of the alarm pheromone. But also plants can emit (E)-β-farnesene, however mostly in combination with other compounds. One compound widely spread in plants is the (E)-β-caryophyllene. In our study we investigated whether the pea aphid's (Acyrthosiphon pisum) behavior differ after the perception of (E)-β-farnesene alone, (E)-β-caryophyllene alone, or different mixtures of both compounds. The two compounds alone, mixtures of the two compounds, and the solvent n-hexane as a control were applied to pea aphid colonies, and the behavior of the aphids was recorded. Results/Conclusions
Pea aphids got less alerted when they perceived (E)-β-farnesene in combination with (E)-β-caryophyllene as when they perceived (E)-β-farnesene alone. The higher the proportion of (E)-β-caryophyllene in a mixture the weaker was the response of the pea aphids. (E)-β-caryophyllene alone had no influence on aphid behavior. These results give insights of a possible plant defense strategy against aphids.