Phenology drives rice-fall armyworm interactions and arthropod community dynamics through foliar volatile signaling

Volatile organic compounds (VOCs) are one of the key mediators of plant-insect interactions. Although several studies have examined the factors affecting volatile-mediated tritrophic interactions, the role of phenology in determining the effects of volatile emission is less understood, especially in rice. Currently, fall armyworm (FAW, Spodoptera frugiperda) is considered a minor pest in rice; however, changes in climatic conditions and the rapid emergence of pesticide resistance can quickly alter this status. To address this, we examined how plant phenology and FAW herbivory affect foliar volatile emissions and the associated arthropod community dynamics in rice.

Among the phenological stages (n = 6 per treatment), the vegetative stage emitted significantly more day volatiles than the reproductive stage. FAW herbivory also induced volatile emission in rice. Furthermore, in the Y-tube olfactometer choice assays, FAW larvae preferred volatiles from the vegetative stage and undamaged plants. After normalizing volatile emissions by plant biomass, the most common volatile compounds emitted included diketone alcohol, ethylhexyl benzoate, and ethylhexanol. In the common garden experiment, more arthropods, regardless of their taxonomic status, were attracted to the vegetative stage, although they were not significantly attracted to FAW-damaged plants. In addition, Diptera was the most predominant order observed, irrespective of the treatments.

Our findings collectively show that phenology is the key driver in mediating volatile-mediated tritrophic interactions in rice. The observed phenology-driven changes in VOC emissions influence differences in arthropod attraction, suggesting ecological consequences in rice-FAW interactions and highlighting the importance of incorporating phenology into sustainable pest management strategies. © 2026 Society of Chemical Industry.