Researchers probing linkages between the two North American strains and the European strain of Phytophthora ramorum – the pathogen that causes Sudden Oak Death – say they have found important clues to their origins. According to a USDA Agricultural Research service press release:
Their evidence showed that the European lineage may be older than the North American lineages, and that the three lineages have originated from three different geographic locations rather than one location, prior to introduction to Europe and North America. There now needs to be even greater caution when approving plant material for introduction into the United States that could introduce additional strains of the pathogen, according to the researchers.
