One of the strategies that plants employ to defend themselves against herbivore attack is the induced production of carnivore-attracting volatiles. Using elicitors and inhibitors of different steps of the signal-transduction pathways can improve our understanding of the mechanisms underlying induced plant defenses. For instance, we recently showed that application of jasmonic acid, a key hormone in the octadecanoid pathway involved in herbivore-induced defense, to Brassica oleracea affects gene expression, hormone levels and volatile emission, as well as oviposition by herbivores and host location behavior by parasitoids. Such defense responses vary with the dose of the elicitor and with time since application. This addendum describes how the use of inhibitors, in addition to the use of elicitors like jasmonic acid, can be applied in bio-assays to investigate the role of signal-transduction pathways involved in induced plant defense. We show how inhibition of different steps of the octadecanoid pathway affects host location behavior by parasitoids.