Diurnal rhythm of volatile emissions from damaged Brachypodium distachyon affects the temporal preferences of tritrophic interactions

Diurnal rhythm of volatile emissions from grasses in response to herbivory may temporally affect the oviposition behaviors of the conspecific herbivores and prey searching of natural enemies of the herbivores in a diurnal cycle of the ecosystem. We assessed volatiles emitted from the temperate grass Brachypodium distachyon L. (Poaceae) damaged by Mythimna separata Walker (Noctuidae), a specialist herbivore of Poaceae, in light/dark cycle conditions. Volatiles were preferentially emitted from the damaged plants in both light and dark phases, but their quantitative compositions were different. The generalist predator Nesidiocoris tenuis Reuter (Miridae) was attracted to the damaged plants in both light and dark conditions. However, adult females of M. separata preferred to oviposit on undamaged plants mostly in the dark owing to the cue of undamaged plant volatiles, partly in a circadian rhythm-dependent manner. The findings suggested that volatiles released in the dark contribute to both plant-herbivore and plant-herbivore enemy communications.