Redwood Reader

The inevitable spread of the invasive tree disease Sudden Oak Death is proceeding in Southern Humboldt. The isolated area around Redway where it was found has grown to about “at least 7 km x 7.8 km (54.6 km2, or 21 mi2) stretching from Sproul Creek in the south to Dean Creek in the northeast, near Briceland in the northwest, and Garberville on the east. Pathologists and foresters from the University of California, USDA Forest Service, and CDF recognize that the disease is operating at a scale that is much more difficult to manage than previously thought.”
After detecting the disease and an experimental treatment in February, 2004, to attempt to control the limited number of infected California bay laurel trees in Redway, survey began to identify the infested area and to test the feasibility of future control treatments using aerial detection, watershed monitoring, and a residential and wildland ground-based survey.
“Partners in this strategy included UC Cooperative Extension (UCCE) Humboldt/Del Norte County, the Humboldt County Department of Agriculture, the UC Davis Department of Plant Pathology Rizzo Lab, the UC Berkeley Garbelotto Lab, the California Department of Food and Agriculture, the USDA Forest Service, the California Department of Forestry and Fire Protection (CDF), Hoopa Tribal Forestry, Yurok Tribal Forestry, the Bureau of Land Management, and numerous private and public landowners who granted permission to survey their properties.”
“Pathologists and foresters from the University of California, USDA Forest Service, and CDF recognize that the disease is operating at a scale that is much more difficult to manage than previously thought.
Management of P. ramorum at a landscape scale has not been attempted before in California. The group recommends an adaptive management approach that attempts to contain the pathogen within the smallest geographic area possible, treating the area much like a wildfire containment area. Experimental treatments will be applied, where landowner permission and funding can be obtained, to the perimeter of the infected areas in the hope of containing the pathogen and preventing spread to other watersheds. Bay and tanoak, the primary hosts for the pathogen in the region, will be removed within this “ridgeline host reduction zone” as the highest priority for treatment. Any new infected areas outside the perimeter will be aggressively treated. Within the perimeter of the infested area, the cooperators hope to compare the success of various treatment approaches as well as reduce inoculum levels in the areas with the greatest apparent concentration of P. ramorum. A detailed report of findings and proposed treatment strategies will be made available soon. For a map of the 2005 Southern Humboldt P. ramorum Survey Status, click here. For more information on the survey or Humboldt’s P. ramorum program, contact UCCE Humboldt/Del Norte’s Yana Valachovic at: yvala@ucdavis.edu or Chris Lee at: cale@ucdavis.edu. “
We applaud the attempt to contain the disease in a geographic locality but doubt it will do much good. There are just too many transmission vectors and insufficient understanding of the movement of the organism. We note the publishing of a book covering nine years of research chronologically. We had noted Dr. Alex Shigo (he calls it California Oak Decline) predicted the existence of native relations to the disease that would hybridize and cause a new set of problems is borne out with one new US phytophthora species and several in Europe.
An earlier article noted lack of SOD in lands burned in the last fifty years. This could be a good management tool, but it raises the specter of stand replacement every fifty years, which would not allow for the full recovery of the soil water storage mechanism. Like harvesting small conifers via clearcut, it is a recipe for continual landscape desiccation, and lowered ability to resist soil movement.
Five new host plants have tested positive for P. Ramorum via pot culture. They are Oregon Ash, Redwood ivy, California nutmeg, maidenhair fern, and Sweet Ciciely.
Representative Pombo has asked the General Accounting Office to report on government responses to invasive species in our forests. They chose Emerald Ash borer, Asian Longhorned beetle and SOD. The first two are complete. GAO reps will be here in late September to gather “insight into how P. ramorum got into the US, what damage it has and could cause, how efforts have minimized its impact to the forests, what risk assessments have been done and used for allocating resources, and what lessons have been learned that will be used to improve this or future responses. The USDA’s APHIS and Forest Service, in cooperation with CDFA, the COMTF, CDF, Native Americans, County Agricultural Commissioners, nursery industry representatives, regulated states, and other stakeholders, are coordinating the compilation of information and site visits for the review.”
Another new species of phytophthora has been recognized in England, and one of its two oaks (Sessile oak, Quercus petraea)has been found infected, symptoms being bleeding trunk cankers.. Other new hosts come from China, Evergreen maple (Acer laevegatum), and Michelia doltsopa, used for landscaping in California.
We are surprised there are no warnings or restrictions coming out because the disease can even spread in cut wood, let alone bark. We would think maybe no wood should come out of the area or it will spread it around Humboldt. Not that it can’t spread in other ways. But we won’t be able to do that if the disease gets into Douglas fir and redwood in a big way or we will lose our timber industry. Fire may be able to contain the outbreak, but that is a large response with an iffy outcome. Fires like the Canoe Creek fire may actually be a better prescription but that remains to be seen.