Protective perfumes: the role of vegetative volatiles in plant defense against herbivores.

Herbivore damage to leaves and other vegetative tissues often stimulates the emission of volatile compounds, suggesting that these substances have a role in plant defense. In fact, ample evidence has accumulated in the last few years indicating that volatiles from vegetative plant parts can directly repel herbivores, such as ovipositing butterflies and host-seeking aphids. Volatiles have also been demonstrated to protect plants by attracting herbivore enemies, such as parasitic wasps, predatory arthropods and possibly even insectivorous birds. Even below ground herbivory results in the release of volatiles that attract herbivore enemies. However, plant volatiles are also known to attract enemies of plants. Hence, to determine the true value of these substances in defense, more research is needed especially in natural communities with non-agricultural species.