Sudden oak death, sudden larch death, and ramorum blight​

Publication Type:

Web Article


American Phytopathological Society: The Plant Health Instructor, The American Phytopathological Society, St. Paul, MN (2019)



Phytophthora ramorum is a recently emerged pathogen with a host range of more than 150 plant species. This fungus-like organism causes sudden oak death on certain members of the oak family and has killed an estimated 30-45 million trees in coastal forests of California and Oregon. The pathogen additionally causes sudden larch death of Japanese larch, especially in conifer plantations in the United Kingdom. On most hosts, however, P. ramorum causes ramorum leaf blight or shoot blight on native plant species and horticultural nursery crops, plaguing some nurseries in California, Oregon, Washington, British Columbia and Europe.