Rice spikelets trap and kill caterpillars using trichomes

Plants possess a suite of traits to defend against biotic and abiotic stressors. Trichomes, the epidermal hairs, are among the most studied surface defenses in plants, that have been shown to have pre- and post-ingestive effects against insect herbivores. Although well studied in dicots, their defense role remains comparatively unexplored in monocots such as rice. Moreover, most studies have primarily focused on leaf trichomes; however, trichomes are also present on floral organs. Here, we show that non-glandular trichomes on rice spikelets act as a strong barrier against fall armyworm (Spodoptera frugiperda) caterpillars, a polyphagous herbivore that can cause significant yield loss. Through a series of behavioral and analytical chemistry experiments, we demonstrate the potential role of rice floral volatiles in guiding the caterpillars, and trichomes in trapping them on the spikelets while feeding, leading to larval death inside the spikelets. This finding provides preliminary evidence that spikelet trichomes may function as a defense mechanism against herbivores feeding on reproductive structures, which should be explored further.