Plants smell different when attacked by exotic herbivores

https://phys.org/news/2017-01-exotic-herbivores.html

Plants smell different when attacked by exotic herbivores

A new study to be published in the scientific journal New Phytologist reveals that plants' odour bouquet changes depending on the type of enemy that attacks it. To the surprise of the researchers involved, native plants emit a special odour bouquet when they are attacked by exotic herbivores.
Plants emit odours to call in reinforcements; for example, to let a parasitic wasp know that a caterpillar is present. This may not help the plant immediately, but in the long run, it means fewer butterflies and voracious caterpillars in the next generation. Dutch field mustard (Brassica rapa) emits different odour bouquets in response to exotic as opposed to native caterpillars, slugs and aphids.