Gnomoniopsis castaneae: An emerging plant pathogen and global threat to chestnut systems

Gnomoniopsis castaneae is an important, destructive pathogen of Castanea species, initially identified as the primary agent of nut rot in Europe and Oceania. Although a decade of research has focused almost exclusively on its association with and activity in chestnuts, it has been identified as a mild pathogen or endophyte in multiple other hardwood species, whose roles as potential reservoirs and hosts have remained unexplored. Although the origin of the disease is unknown, it is thought to be a ubiquitous endophyte that has potentially shifted to pathogenic activity as a result of global climate change. Yet there is evidence of the expansion of the range of the pathogen as it continues to be identified in new regions, suggesting some degree of introduction is occurring. Its recent discovery in the United States brings a new urgency to the need to understand the full range and epidemiology of G. castaneae and to examine potential methods of detection and mitigation.