Sudden Oak Death -- The Political Tree Disease
By Tom Gaman
Article from Distant Thunder, Journal of the Forest Stewards Guild Dec. 2003
What’s in a name? Had the vernacular for Phytophthora ramorum been “phytor” or another nondescipt name, would it now be among the list of common tree diseases of the urban forest footnoted in arborist reports and forest management plans?
Instead it became “Sudden Oak Death” and it killed wild land trees in expensive neighborhoods. Homeowners envisioned a near future of devastated landscapes barren of vegetation. The scare brought County Supervisors, California’s Governor and even US Senators into the act, talking about love for trees and providing tens of millions of emergency dollars, and millions more in ongoing funds for SOD in California. The agencies responded by staffing long-vacated positions, establishing task forces, declaring quarantines, drafting regulations, issuing press releases, chartering air reconnaissance missions, purchasing computers, funding graduate students’ research projects, building websites and holding long meetings. In response to an outpouring of public fright, California’s oak woodlands finally have a poster child.
New diseases pop up frequently in a mobile world and so SOD is not a great surprise to plant pathologists. A number of agencies routinely do pest risk assessments when new plant pathogens appear--Phytophthora ramorum classifies in “very high” current risk category. The research has told us that SOD is everywhere. The fungus attacks a laundry list of native species and introduced plants in 14 plant families, including redwood and Douglas-fir, and no artificial cure is known. SOD seems to like moist temperate forest settings without annual extremes in temperature. Coastal tanbark oak (Lithocarpus densiflora) is the most susceptible species because both the foliage and inner bark become infected. Oaks in eastern US may even be susceptible.
The new fungus must persist within ecologically diverse wildland settings, and, though thousands of trees have died in coastal California, this is unlikely to become a killer like chestnut blight or Dutch elm disease. Though extensive stands of tanoak were killed in Big Sur, it turns out that the “oak death” does not render a mortal blow to most species. Nonetheless, SOD is naturally self-dispersing and reproduces easily within a broad host range now extending to Oregon and Washington, Canada and Europe—one that is probably being expanded by global warming trends.
Life, even for California’s millions of susceptible oak trees, goes on. While SOD attracts attention, the lion’s share of California’s oak mortality is due to bulldozer operators, vineyard conversions, herbicide applications, urban sprawl, and industrial fuel wood harvests. In California, famous for the strictest forest practice rules in the world, the irony is that millions of acres of oak woodlands receive no protection.
Tom is a consulting forester with East-West Forestry Associates, Inverness, California (see www.forestdata.com) and he is vice president of the California Oak Foundation .