Trees Continue to Suffer From Mystery Disease
by Win Smith
California Oak Mortality Task Force
Biomass Utilization Committee
In 1995, the first discoveries of Sudden Oak Death (SOD) syndrome were restricted to tanoaks and coast live oaks in Marin County. Since then, this devastating fungal disease has spread from these two tree species to fifteen shrub and tree species in ten California counties and in Southern Oregon. The latest scientific find, in December 2001, has identified Sequoia sempervirons, the Coast Redwood, as a possible host tree.
Of the fifteen species known to be susceptible to the fungus (Phytopthera ramorum), great numbers of coast live oak, black oak, and tanoak have succumbed to the disease. The deaths of these fungus-infected trees are usually expedited by the invasion of oak beetles that rapidly girdle the trunks and stop the transportation of nutrients to the trees. The other twelve species are Phytopthera ramorum host plants.
Combatting the SOD problem and its spread
At this time, there is no known treatment to eradicate SOD, nor is there a methodology for preventing its spread. However, governmental agencies are involved in the search for solutions to prevent this continued assault on the forests of Northern California and Oregon.
Plant pathologists are working diligently to find a curative agent for the fungus. They also are investigating new hosts, and are working with University of California Extension offices in the infected counties to identify new outbreaks or a spread of the disease in the field. To illustrate the seriousness of the SOD problem locally, on Sonoma Mountain, 8 of the 9 predominant tree species are either host trees or are susceptible to mortality if infected.
One of the major concerns of those involved in the SOD battle is the growing buildup of dead wood accumulation on the forest floors, which will increase fire hazard levels and adversely affect fire behavior in wildland fire events. This early winter has toppled significant numbers of dead trees on Sonoma Mountain and more will likely fall as winter progresses. All this dead material becomes a new fuel bed for fire extensions into standing tree canopies.
How do we deal with large volumes of this infected organic material? In August 2000, the California Oak Mortality Task Force (COMTF), a non-profit consensus group, was created to develop approaches to address Sudden Oak Death. The Biomass Utilization Committee of COMTF is studying and developing strategies for the disposal of the dead material. One concept is energy co-generation through incineration, another is composting. Early test results look promising. Where possible, onsite brush burning and "bucking up" tree trunks and limbs for firewood is another solution.
The clean up and removal of dead trees in areas of concentrated losses will be logistically difficult and expensive, particularly for individuals owning large tracts of dead trees. How will these clean up programs be accomplished? By landowners? By the public? Or jointly, with the landowner and the public sharing the responsibility and costs? This is, potentially, an enormous problem in the infected counties.
Pathogen Spread
The spread of the SOD pathogen is not fully understood, and one of the big questions is whether it is natural or human caused. Research indicates that Phytopthera ramorum can possibly be spread in runoff waters. The possibility exists that the pathogen is wind borne from host to uninfected plants, is carried by wildlife between infected and uninfected areas, or is transported on vehicular tires, or on the boots and tools of individuals.
The California Department of Food and Agriculture is working on an Oak Mortality Disease Cooperative Project Permit Agreement for those individuals or business entities that will be moving infected oaks or oak products, as well as on mitigating protocols to prevent spread of the pathogens. At this time, firewood production is occurring in infected areas and wood and its products are being moved into uninfected areas. The permit process will regulate these activities and will be controlled by county agricultural commissioners in SOD regulated counties.
Although the SOD spreading mechanisms are basically unknown, some park administrators of publicly owned recreation areas have denied access to infected areas within parks, fearing further SOD spread in their jurisdictions. This reasonable land management policy has not been followed by other agencies, as the actual mode of spread has not been adequately identified. Additionally, the concept of decontamination stations on publicly utilized properties has been considered and in some areas instituted to prevent pathogen spread.
Oak Woodland Restoration
In recognizing the potential of loss of wildlife habitat, the replacement of the natural plant communities with exotic and opportunistic plant species, the loss of property values, possible land use conversions, and increased fire hazards as a result of SOD infestation, the Biomass Utilization Committee members expressed a concern and a desire to restore lost oak woodlands.
At the November 2001 California Oak Mortality Task Force meeting in Petaluma, a Restoration Subcommittee was established to develop restoration guidelines for public usage. This group is presently working on this issue and anticipates a draft document in late winter or early spring of 2002. It is an interesting study as restoration guidelines are multi-faceted and need to be tailored to specific sites.
Financing
How are research, SOD monitoring, and educational and hazard reduction programs currently being financed? Early costs had been absorbed by each agency working on the problem. Quickly, as new outbreaks and hosts were found and new counties were drawn into the fray, public monies were appropriated at the state and federal levels and by a private foundation. In the fall of 2001, funding exceeded 9 million dollars.
As a result of the preliminary findings that the Coast Redwoods might be susceptible to Sudden Oak Death, on January 10, 2002, Senator Barbara Boxer requested of the Department of Agriculture a five-year $70 million appropriation to combat the disease and find mitigating agents.
Conclusion
Sudden Oak Death is a very serious problem, the likes of which none of us has ever experienced. If not controlled, Sonoma Mountain's landscape, our state economy, our biotic communities, and our ways of life will change drastically. It is our responsibility to understand the disease, to follow best management practices to minimize pathogen spread, to report any signs and symptoms of SOD that we might observe and to get involved in the process of eradicating this insidious disease.
Additionally, it would be advisable to stress to your elected representatives the importance of continued funding for SOD research, eradication and disposal until this problem is solved.
Sources of Information
For more information regarding Sudden Oak Death, please note the following sources: