Lessons from the Far End: Caterpillar FRASS-Induced Defenses in Maize, Rice, Cabbage, and Tomato.

Plant defenses to insect herbivores have been studied in response to several insect behaviors on plants such as feeding, crawling, and oviposition. However, we have only scratched the surface about how insect feces induce plant defenses. In this study, we measured frass-induced plant defenses in maize, rice, cabbage, and tomato by chewing herbivores such as European corn borer (ECB), fall armyworm (FAW), cabbage looper (CL), and tomato fruit worm (TFW). We observed that caterpillar frass induced plant defenses are specific to each host-herbivore system, and they may induce herbivore or pathogen defense responses in the host plant depending on the composition of the frass deposited on the plant, the plant organ where it is deposited, and the species of insect. This study adds another layer of complexity in plant-insect interactions where analysis of frass-induced defenses has been neglected even in host-herbivore systems where naturally frass accumulates in enclosed feeding sites over extended periods of time.