Lepidopteran pests and phytopathogenic fungi: The overlooked interface of insect‒microbe interactions.

Lepidopteran pests and phytopathogenic fungi are major biotic threats to crop health and productivity, yet their interactions remain poorly integrated into current frameworks of insect-microbe and plant disease ecology. Lepidopteran pests and fungal pathogens often share common ecological niches on host plants, particularly damaged tissues and microbe-rich interfaces. Chewing damage, frass deposition and movement by lepidopteran pests can create opportunities for fungal dispersal and invasion. This review synthesizes current knowledge on lepidopteran pest-phytopathogenic fungus-plant (LPP) tripartite interactions. It first outlines the biological features of lepidopteran pests, phytopathogenic fungi, and host plants that provide the ecological basis for their co-occurrence. Direct interactions are then examined, including competition for plant-derived resources, pest-mediated fungal facilitation, mutualistic associations, and antagonistic effects of fungi on lepidopteran survival or development. Plant-mediated indirect interactions are further discussed, focusing on how pest feeding or fungal infection reshapes host-plant physiology, defense responses, and ecological signaling. Finally, interaction-guided strategies are considered from three perspectives: breeding crop varieties with coordinated resistance, applying RNAi-based approaches to target key pest or fungal genes, and manipulating plant- or insect-associated microbial communities. Overall, understanding the pest-fungus interactions shifts the paradigm from isolated threat management toward holistic interventions, providing a mechanistic foundation for next-generation sustainable crop protection.