Introduction
Wild plants have evolved intricate defence mechanisms
against insect herbivores [1–3] over a period of 400 million
years [4]. These depend partly on primary recognition of
the insect mediated by specific herbivore-derived mole-
cules, termed herbivore-associated molecular patterns or
HAMPs [5,6,7]. Induced defence occurs after recogni-
tion of insect attack and includes ‘indirect defence’
entailing the emission of herbivore induced plant vola-
tiles (HIPVs) that allow them to attract parasitoid and
predator insects that are tuned in to these signals and use
them when foraging for prey insects