An aggressive strain of Phytophthora ramorum — the pathogen responsible for sudden oak death — has been identified in Douglas fir and grand fir samplings in southwest Oregon. The EU1 strain, previously reported in Europe, is said to spread more aggressively than its North American counterpart, but Jared LeBoldus, a forest pathologist with Oregon State University, emphasizes, “It’s important for people not to get overly worried or concerned. This pathogen is spreading, but the effort that we have put forward into managing this disease has slowed it down significantly.”
It takes about two years for P. ramorum to kill a tree, and so far there have been no reports of dead Douglas fir or grand fir. “Because this is new to fir trees in Oregon, we don’t really know what is going to happen,” LeBoldus said. “There have been cases in Europe where this strain has killed Douglas fir. We’ve been looking at different host ranges and other species of trees that have been infected. We’re trying to determine if this will be more of a threat to Oregon forests than the North American strain.”
Sudden oak death was first reported in North America in 1995 in Mill Valley, California. In 2001, OSU forest pathologist Everett Hansen, now retired, identified what was killing trees in forests in southwest Oregon and led an aggressive program to eradicate the disease. In 2004, USDA formed a rapid response project to limit the spread of sudden oak death in nurseries across the country.
In 2012, a rhododendron suffering from sudden oak death was reported in a Curry County ornamental nursery. Genetic testing in the USDA-ARS Horticultural Crops Lab in Corvallis determined that the pathogen wasn’t the same one as discovered in North America, such as the one that appeared in Oregon in the 2000s.
That strain spread to a tanoak in the forest near the nursery in 2015 and then to Douglas fir and grand fir saplings over the last two years. Symptoms in fir include wilted tips, brown discoloration of needles and needle loss on young shoots.