Foliar application of Cis-jasmone affects oviposition behavior and feeding of Spodoptera exigua (Lepidoptera: Noctuidae)

The role of cis-jasmone (CJ) as a semiochemical and inducer of plant defense is well documented in the literature. In a previous study, we reported increased emission of certain volatile organic compounds (VOCs) in the headspace of CJ-treated tomato plants upon larval feeding, some of which are known to mediate plant-insect and tritrophic interactions. However, it remains unclear if application of CJ to plants would have consequences on the fitness of insect herbivores. Using the generalist herbivore, Spodoptera exigua (Hübner), as a model, we tested the hypothesis that foliar application of CJ would prime plant defenses against insect herbivores. First, the oviposition preference of S. exigua females was compared between filter paper substrates permeated with headspace VOCs from CJ-treated tomato plants versus untreated plants, both with larval infestation. Next, the feeding response of S. exigua larvae was quantified on CJ-treated plants compared to untreated plants. S. exigua females deposited fewer eggs on substrates permeated with VOCs from CJ-treated plants than on substrates permeated with VOCs from untreated plants. In addition, S. exigua larvae showed reduced feeding and significantly lower body weight on CJ-treated plants compared to untreated plants. Liquid chromatograph coupled-mass spectrometry (LC-MS) analyses showed increased accumulation of jasmonic acid in CJ-treated plants compared to untreated plants, following herbivore infestation. These results indicate that exogenous application of CJ can prime tomato plant defense against insect herbivory with potential ramifications for herbivore oviposition and feeding. These findings are discussed in relation to the potential use of CJ to manage agricultural pests.