International movement of plant material is regulated by national plant protection organizations, and depends on the accurate identification and diagnosis of pathogens of concern. However, current lists of regulated pathogens contain several ‘phantom’ agents which impede access. Phantom agents are presumed pathogens described on the basis of limited reports of plant symptoms, but there is no biological data to confirm that these pathogens exist. In order to show that imported plant material is free of these phantom agents, additional testing such as biological indexing may be required by regulatory agencies before the release.
A team of over 180 researchers from 40+ countries, including several NCPN scientists, addresses the challenges posed by “phantom agents”— putative pathogenic agents named in literature without supporting data on their existence. Those agents remain on regulatory lists, creating barriers in trade and plant certification. Historically identified based solely on symptoms, these agents lack isolates or sequence data, making reliable detection or risk assessment impossible. After reviewing over 120 such agents across 10 key plant genera, this paper recommends their removal from regulatory lists and calls for revised standards aligned with modern diagnostics. These recommendations support updated import requirements for citrus, grapes, berries, pome and stone fruits, and roses. This effort seeks to streamline germplasm exchange, benefiting global agriculture by removing the constraints imposed by phantoms. The publication, “Streamlining Global Germplasm Exchange: Integrating Scientific Rigor and Common Sense to Exclude Phantom Agents from Regulation” will soon be available from the scientific journal Plant Disease.
