Chemical cues linked to risk: cues from belowground natural enemies enhance plant defences and influence herbivore behaviour and performance

1. Chemical cues are essential for many ecological interactions. Previous studies of chemically mediated multitrophic interactions have typically focused on responses to cues from plants or herbivores aboveground. It is increasingly clear, however, that belowground cues and those produced by organisms at higher trophic levels also have ecological importance. Prey animals often avoid predator odours to improve survival, and previous research documented enhanced plant resistance following contact with belowground natural enemies, though the ecological basis was unknown.

2. Here we investigated plant and insect responses to chemical cues from belowground natural enemies and explored the ecological significance of these cues for multitrophic interactions. More specifically, we examined the influence of odours emitted by entomopathogenic nematodes (EPNs), a natural enemy of insect herbivores, on the performance and behaviour of their insect prey and the defence responses of nearby plants....