Infochemical Webs and Tritrophic Interactions

Abstract Plant volatiles mediate tritrophic interactions between plants, herbivorous arthropods and the carnivorous natural enemies of herbivores in various ways. These volatiles are classified into two categories: herbivore‐induced plant volatiles (HIPVs) and constitutively emitted plant volatiles. Herbivores and carnivores use these plant volatiles as information for effective foraging. Consequently, infochemical webs based on the multifunctional aspects of HIPVs can be constructed. This article reviews the ecological function of plant volatiles in a single tritrophic system and the effects of the coupling of two tritrophic systems on the function of plant volatiles with emphasis on the infochemical webs in tritrophic systems. Furthermore, prospects for the application of HIPVs that attract specific natural enemies are discussed. Key Concepts: In response to herbivore‐induced damage, plants emit the so‐called ‘herbivore‐induced plant volatiles (HIPVs)’ that are not naturally emitted from plants or in many cases emitted only in trace amounts. The mixtures of HIPVs vary according to the type of plants: herbivores and carnivores. Both HIPVs and constitutively emitted plant volatiles are separately and/or simultaneously used by both herbivores and carnivores to form infochemical webs. Coupling the two tritrophic systems on the same plants affects the infochemical webs of each tritrophic system either positively or negatively. HIPVs would be a new tool for biological control. This requires comprehensive studies on the target agroecosystem.