The Sublime Art of War: Herbivore-induced Plant Volatiles

Volatiles released from insect herbivore-damaged plants can attract a third trophic level of parasitoids and predators that prey on the attacking insect. Known as the ‘indirect defense response’ of plants to insect attack, the production of herbivore-induced plant volatiles (HIPVs) requires complex signal cascades in the leaf being attacked, which then spreads to the entire plant, resulting in systemic production of volatiles. To use the parlance of JRR Tolkien, HIPV production in a leaf ‘lights the beacon’ that attracts allies (predators and parasitoids) to the battleground. The saliva of a caterpillar or even the cement that binds the eggs of a female butterfly to a leaf surface contains distinct elicitors (such as fatty acid-amino acid conjugates) that can stimulate the release of HIPVs. These complex bouquets of plant volatiles can repel further insect attacks and potentially warn undamaged neighboring plants. HIPVs have applications in the sustainable management of agricultural pests, such as the ‘push-pull strategy’ used by farmers in Africa. This brief article provides an augenblick on the intriguing role of HIPVs as an important component of plant-insect interactions and the defense arsenal of plants against attacking insect herbivores. © 2024, Indian Academy of Sciences.