Sudden oak death: issues and implications for management, policy and society

Susan J. Frankel

Tuesday, October 01, 2002

Susan J. Frankel
Plant Pathologist
USDA Forest Service, State and Private Forestry, Pacific Southwest Region, Vallejo

For the next hour, I will take you through the progression of sudden oak death from the late 1990s when the disease erupted as a dramatic urban forest die-off, to today when it threatens trade and commerce of Douglas-fir and coast redwood. This talk focuses on the implications of sudden oak death on forestry, horticulture, and agriculture, what the disease means for management, policy and to society. My goal is for each of you to leave here with a better understanding of sudden oak death so you can infer how Phytophthora ramorum may impact your particular concerns: your neighborhood, professional activities and attitudes.

To understand the implications of sudden oak death on management and society, one must first understand sudden oak death. Phytophthora ramorum, the cause of sudden oak death, has been described as the Godzilla fungus, evil sister, predator, scourge, or deadly plague that has sucked the life out, laid waste, or ravaged its victims, rampaged and denuded forest lands. Many authorities worldwide have predicted that sudden oak death may be worse than Dutch elm disease, or the next chestnut blight.

Sudden oak death earned its reputation as a "Godzilla fungus" in the late 1990s, when coastal California experienced El Nino conditions, with many areas getting twice their average yearly rainfall. There was a tremendous increase in the number of dead trees in Marin and Santa Cruz Counties and in Big Sur (Monterey County). Mortality was first noticed in tanoak (Lithocarpus densiflorus). Then, coast live oak (Quercus agrifolia), a symbol of the natural beauty of California with a natural bonsai form, was recognized as dying-off. Entire neighborhoods were impacted. You can imagine the shock and fear, to see the forest, normally long-lived, die-off and not know why, when, if it would stop, and how it would ultimately impact the forest. This die-off occurred in an area where over 7 million people live, a community of well-educated, environmentally aware, politically well-connected people. They were outraged that more had not been done. They were afraid, not knowing what to do to save their trees and protect their homes from fire and falling tree trunks.

It is this early image of sudden oak death that has captivated the media and citizenry. In the late 1990s P. ramorum showed that it can be a devastating, virulent pathogen. But for the past two years, P. ramorum mortality has slowed in many areas, while the "fear factor" has escalated. I am not here to minimize the threat from sudden oak death, it is very real, wide reaching and extremely disconcerting. But the infested landscapes of Marin, Santa Cruz and Monterey Counties are not barren and species are not being driven to extinction.


Sudden oak death is caused by a newly discovered pathogen, Phytophthora ramorum, identified by David Rizzo, UC-Davis and Matteo Garbelotto, UC-Berkeley in June 2000 (Rizzo and others 2002). Shortly after it was found in California, it was determined that the same, or a very similar, organism was found in 1993 in Germany and the Netherlands on rhododendron (Werres and others 2001). The damage on rhododendron was limited to twig dieback and leaf spots in nurseries, parks and gardens. Rhododendrons are not native to Europe and the damage was minor, so the European scientists paid little notice to the pathogen until the connection was made to oak mortality in California.

Phytophthoras (the genus name means "plant destroyer") are among the most damaging plant pathogens worldwide, most notably Phytophthora infestans, which caused the Irish potato famine. These pathogens are not classified as fungi - they are brown algae and possess motile "swimming" spores that can propel themselves in water.

Since P. ramorum is new, we are just starting to understand its interactions with climate, vegetation, and other organisms. While we have learned a lot in a few years, we are continually surprised and everything I say today is footnoted with caution. There is a high level of uncertainty and much more research is needed to fully understand the phenomenon dubbed sudden oak death. It is humbling to pause and acknowledge that it is possible that many of our theories may be incorrect. However, we cannot wait until all the data is collected and analyzed before we take action. The pathogen is spreading, trees are dying, and other countries are banning imports of California-grown forest products, ornamental and agricultural plants. We realize that at this point in our understanding we are not even asking all of the right questions to direct research. Much of the challenge of addressing sudden oak death comes from having to implement policy and forge management programs with limited knowledge, a high level of uncertainty, an intense spotlight on our work, and the need to continually update information and recommendations as the story unfolds.

What is sudden oak death? It isn't sudden, it isn't only on oaks, and it isn't always fatal. Seventeen species are known to be susceptible to Phytophthora ramorum: coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), Shreve's oak (Quercus parvula var. shrevei), tanoak (Lithocarpus densiflorus), madrone (Arbutus menziesii), California bay laurel (Umbellularia californica), rhododendron (Rhododendron spp), big leaf maple (Acer macrophyllum), California buckeye (Aesculus californica), huckleberry (Vaccinium ovatum), California coffeeberry (Rhamnus californica), California honeysuckle (Lonicera hispidula), manzanita (Arctostaphylos manzanita), toyon (Heteromeles arbutifolia), Douglas-fir (Pseudotsuga menziesii), and coast redwood (Sequoia sempervirens). Viburnum (arrow wood) is known to be susceptible in Europe but has not been observed infected in the United States. The pathogen impacts each of these plants differently and research is on-going to determine the epidemiology of the pathogen on each of these hosts, but they may be lumped in two general categories - bark vs. leaf infected.

On coast live oak and California black oak, the pathogen causes a disease of the bark; the cankers caused may result in tree death. On rhododendron and California bay laurel and many of the other hosts, the plant is usually not killed but can serve as reservoirs of inoculum (Davidson and others 2002b). The pathogen infects the leaves and can rapidly reproduce on leaves under moist conditions. Jennifer Davidson, USDA Forest Service researcher stationed at UC-Davis with David Rizzo, has shown that these spores can move in windblown rain and if they intersect oak trunks in large numbers, they may enter the trunk through natural openings in the bark. Of course nothing is clear-cut, tanoak fits in both categories - the leaves are infected, the pathogen sporulates on them and the bark is also killed. This combination may partly explain why tanoak is so susceptible.

On coast redwood, the pathogen has been recovered from blighted basal sprouts and from needles and twigs (Garbelotto and Rizzo 2002). There is no indication that the pathogen can kill mature redwood. We have been observing redwood forests with heavily infested understory tanoak for almost 10 years; so far the redwoods appear to incur only minor damage. A decade is not a long time in the lifespan of a redwood tree and the possibility remains that over time the pathogen will grow in redwoods and could eventually kill trees. Further investigations of how the pathogen grows in redwood are needed before we can fully understand the threat to redwood.

In one area in Sonoma County beneath heavily infested California bay laurel trees, a few Douglas-fir are dying back from the top due to P. ramorum. The impact is similar to damage from twig girdlers. Again, the trees are not dying, but a few branches are damaged. Log inoculation studies by Everett Hansen at Oregon State University (Hansen and Sutton 2002) also indicate that Douglas-fir is susceptible. Further investigations are needed to determine to what extent Douglas-fir will be impacted. So far our observations indicate that most Douglas-fir will tolerate infection or avoid the disease altogether. The only known infested Douglas-firs are relatively small understory trees and Douglas-fir are present on many other infested sites without apparent infection.

Phytophthora ramorum has been found in 12 counties in California and near Brookings, Oregon. The disease is common in Marin, Santa Cruz, and parts of Sonoma and Monterey Counties. In the other eight infested California counties, it is limited in its distribution (See for more details).

P. ramorum was detected via aerial survey in Oregon in August 2001. A relatively small area (less than 40 acres) was identified and the Oregon Department of Agriculture, USDA Forest Service, Oregon Department of Forestry, and Oregon State University worked together to attempt to eradicate or slow the spread of the pathogen. In 2001, they removed all the hosts, broadcast burned, and set up a monitoring program for the diseased areas. In 2002, the disease was found on a few mature tanoak trees in the same general area. These trees were removed, about 20 additional acres were treated. The tanoak in the treated area, are sprouting and intensively monitored. Most tanoak sprouts are uninfected but a few infected sprouts were destroyed. (Goheen and others 2002, personal communication Everett Hansen, Oregon State University).

California, the United States, Oregon, Canada, Australia, South Korea and the United Kingdom have imposed quarantines to prevent movement of the pathogen on commodities. The details of the quarantines vary. I will cover some of that later but basically most of the quarantines define a "regulated area" in California comprised of the 12 county "infested" area and restrict movement outside the area for commodities made from the 17 hosts and the associated soil. Until recently, Canada quarantined the entire state of California and all plants grown in soil, not just susceptible hosts (

Where did this new organism come from?

No one knows where P. ramorum originated from and when or where it first arrived in California. A compelling theory is that it arrived on, or is somehow associated with, rhododendron nursery plants. Rhododendrons are known to be excellent hosts of Phytophthoras. At least 10 species of Phytophthora have been isolated from rhododendrons, sometimes more than one species on a single plant (Sinclair, Johnson and Lyons, 1987). Early in the sudden oak death outbreak, the owner of a large wholesale rhododendron nursery near Santa Cruz reported death of an alarming number of oak trees surrounding his nursery. Eventually, Rizzo and Garbelotto recovered the pathogen from rhododendrons plants in the nursery.

It made me wonder if we are watching history repeat itself. The most similar forest disease problem to sudden oak death is Port-Orford cedar root disease in Southwestern Oregon and Northwestern California. Port-Orford cedar root disease is caused by Phytophthora lateralis, an organism that DNA evidence indicates is closely related to P. ramorum. No one knows the origin of P. lateralis, but the first report was outside a rhododendron nursery in Washington State in the 1923. Since then, the pathogen moved on ornamental plantings of Port-Orford-cedar south into Oregon and reached Port-Orford-cedar's native range in 1952 near Coos Bay, Oregon. Since the 1950s, P. lateralis has progressed further south into California and infests much of the tree's native range, and has killed thousands of these beautiful and valuable trees (Hansen and others 2000).

Back to that rhododendron nursery in Santa Cruz with P. ramorum, the nursery is surrounded by dead tanoaks and oaks for more than 10 miles in all directions. There also is circumstantial evidence that the Big Sur infestation started from truckloads of rhododendron plants shipped from the nursery and planted around a resort at Big Sur. There are examples of landscaping plants in Marin County that may have started Marin's infestation but it is a larger community, so it is harder to track.

I caution that this is all speculation, but it fits well and it is plausible that landscape plants started this and the Port-Orford-cedar root disease problem. To protect our forest, we must better monitor the health and disease status of nursery stock and carefully regulate importation and movement of nursery stock.


To give you a glimpse into the difficulties of trying to understand Phytophthora ramorum lets look at big leaf maple in the Sierra foothills. Infection on big leaf maple has raised many questions and has been very difficult to diagnose. The first report of P. ramorum in the foothills of the Sierra Nevada resulted from maple leaves collected by Sandy Purcell on his way back from a fishing trip. Dr. Purcell, from UC-Berkeley, works on Pierce's disease, caused by Xylella, a bacterium vectored by glassy-winged sharpshooters, that is killing grape vines. Xylella infects many hardwoods in the east, including maples. The symptoms are a scorch or leaf tip burn. Purcell collected some scorched maple leaves to check for Xylella and decided to give them to the Rizzo/Garbelotto labs to test for P. ramorum. The leaves, collected on the Tahoe National Forest, near Auburn tested positive for P. ramorum via PCR (molecular testing like DNA fingerprinting). P. ramorum is difficult to isolate from maples. The Garbelotto lab successfully recovered the pathogen for the first time from maple leaves collected in Big Sur (Monterey County) in May 2002. There are symptoms of P. ramorum in the Sierra foothills but since the pathogen has never been successfully isolated or cultured from Placer County, it is not included in the quarantine area and not recognized as an infested area. Still the question persists, is the Sierra Nevada climate capable of supporting conditions to favor the infection and mortality of trees (California black oak or tanoak) in the foothills? The area that tested PCR positive near Auburn supports many of the hosts, in addition to big leaf maple, such as bay, manzanita, tanoak, toyon and others.

Confusing the issue is an extremely common discoloration of maples called maple scorch. Maple scorch is present in many areas of California; pretty much everywhere big leaf maple grows. No one knows what causes it - and it can co-occur on leaves infected with P. ramorum. It makes detecting P. ramorum very difficult. This summer we did an early detection survey in the Sierra Nevada, sampled bay, maple and other hosts from the Plumas to the Sierra National Forest. The results are still pending from the Rizzo and Garbelotto labs, but our preliminary observations indicate that the Sierra Nevada foothill forests appear, in general, healthy. In many ways it was refreshing, after viewing the forests in Marin and Santa Cruz Counties that are heavily impacted by sudden oak death.

More than one Phytophthora

Another complication in our understanding of sudden oak death is the recovery of several other Phytophthora species associated with some of the bark cankers and nearby bay foliage. Phytophthoras are soil and waterborne organisms and traditionally pathologists have looked for and recovered them from soil, streams, and plant roots. The Rizzo and Garbelotto labs, Everett Hansen's group at Oregon State University, and others started noticing foliar Phytophthora infection first in rhododendron, then huckleberry and bay. Once they started to analyze foliage in the lab they found several new Phytophthoras in addition to P. ramorum (Davidson and others 2002a). These Phytophthoras appear to be less virulent than P. ramorum, but are occupying a similar ecological niche. It has raised many questions: How are they all related? Are these native species? How do they interact? Could they be the origin for P. ramorum? A foliar Phytophthora has been found in New Zealand and forest pathologists are searching forests worldwide for Phytophthoras in foliage. It has opened an entirely unexplored area, to look at the foliage, not just the roots for Phytophthoras.

We've gone over the hosts, speculated on where the pathogen came from, and gone over some complexities. Now I want to go over some observations to put sudden oak death in perspective and further define what sudden oak death is and its impact.

Not all trees that die and not all branches that break are a result of sudden oak death. Oak trees die from other factors and every tree problem is not sudden oak death. The oak forests of Marin County (China Camp State Park for example) are overstocked; the trees are growing and increasingly competing with one another for space, light, water, and nutrients. Fire suppression, fragmentation and urbanization have stressed these forests. These stresses increase susceptibility to pathogens and insects. There are many other fungi present - canker rots and Armillaria root disease in particular that are gradually eating away at the trees and eventually killing them.

I want to be clear, we do not think Phytophthora ramorum is a stress pathogen. It is most common in wetter areas, where trees are under less water stress (Swiecki and Bernhart 2002) and on trees along forest edges with broad canopies (Kelly and Meentemeyer 2002). We think that may be due to the likelihood of spores intercepting the tree crowns. Nearness to California bay laurel that serve as reservoirs for infection is also a significant risk factor.

Not all bleeding trees will die from infection. Plant species will not become extinct due to sudden oak death. In the hardest hit areas, individuals endure. P. ramorum in the late 1990s infected more than 75% of the host trees in many areas. It was very common and widespread. But many of the bleeding trees are still showing green crowns. There is a wide range in reaction from tree to tree. It seems the most susceptible individuals did appear to die somewhat suddenly with a rapid crown color change from green to yellow to brown in a few weeks (that gave sudden oak death its name). In other trees, the crowns slowly fade and the trees gradually die over a few years. In oaks and tanoak, sudden oak death is a disease of the bark. The pathogen kills bark tissues, creating cankers, which can eventually girdle the tree and kill it. In some trees the necrotic areas do not expand as quickly and the trees seem to be able to live with it. Also, bleeding can be due to many irritants, not just Phytophthoras.

The disease is not denuding acres and acres of forestland. The disease is patchy. Not far from areas with mortality are areas that appear disease-free. We do not understand all the mechanisms for disease spread and under what conditions infection can occur so we cannot accurately predict what those areas will look like in 10 or 20 years.

If conditions are dry, the disease will not cause widespread mortality. The disease will kill large numbers of trees only in areas with lots of moisture. Watching the disease over the past four years indicates that there are climatic factors that drive the disease process. Phytophthoras are water-borne organisms that reproduce in moisture. It seems that El Nino conditions, elevated rainfall-levels, or perhaps fog may be needed for the pathogen to infect trees.

In coastal California, the threat from Phytophthora ramorum is like the threat of earthquakes. The threat is real, but dramatic damage will be episodic. Most forest diseases increase and decrease due to climatic factors, and sudden oak death is no exception. In 1998, 1999, and 2000, mortality was spectacular in both tanoak and coast live oak, but if you look at "hot spots" over time they are not expanding as fast we first feared. This year, the disease appears to be spreading faster in Big Sur than in Marin County, but we don't understand why.

Patchy and episodic, not all infected trees die - why the big deal? Why should we invest in research and management for a tree disease on weed species and ornamental trees? For many reasons: its broad host range including coast redwood and Douglas-fir, the potential for the pathogen to move to new ecosystems in the rest of the United States (and the world) where it may kill valuable oaks in the commercial hardwood region, and to understand the impact of exotic pests and prevent future invasions. But let's hold that question for now, since the answer will be clearer after we look at the impacts sudden oak death has had on forestry, horticulture and agriculture.

What are the impacts of sudden oak death on wildland management?

Since P. ramorum is primarily infesting urban-wildland interface forests, the biggest impact to wildland managers comes from the quarantines, rather than from the disease itself. The Federal quarantine (and soon the state regulations as well), cover soil from the entire county once the pathogen has been recovered. For example, P. ramorum was recently found in Humboldt County near Redway. From preliminary surveys, the infestation appears to be relatively small, covering a few square miles. But the quarantine covers all of Humboldt County, so the Six Rivers National Forest which is over 100 miles from the infestation must change its firewood permitting program, special use permits, botanical collection permits, and agreements with tribes for collection of plants of cultural significance. Landslide repair, construction activities, hunters, off-road vehicles, mushroom collectors, range animals, hikers, bicycle riders, campers and cabin residents all may move soil that can carry infested plant parts, so all those activities and operations are regulated. It is a difficult charge to figure out a practical way to comply with and enforce the quarantine.

The quarantines must also be complied with on private lands, so the State Board of Forestry and Fire Protection created a Zone of Infestation for Sudden Oak Death covering the 12 infested counties. In the 12 counties, all timber harvest plans must include measures to mitigate adverse impacts, such as pathogen spread that might result from timber operations even if the sales are not removing hosts.

Most of the recommended measures are common sense: inspect loads and equipment prior to leaving the site to ensure host foliage is not inadvertently transported; educate employees to recognize symptoms, to know if sudden oak death is in the vicinity of the project, and that a quarantine is in effect and what restrictions apply. The impact of these rules is some additional cost and difficulty in carrying out timber harvests, but they have not been too burdensome. Most foresters understand the need for the restrictions and are motivated to protect forests from further damage.

To manage operations to prevent pathogen spread, first you should survey and know where the disease is. Employees need to be trained in sanitation and quarantine compliance so their activities are not spreading the pathogen. Harvests should be avoided in infested areas by considering what other available lands can be substituted. But most of these considerations are not being implemented at this time because most of the infestation is in open space, parks or non-industrial private lands.

Sudden oak death may increase the need to wash vehicles and equipment prior to moving long distances. Measures to clean fire trucks and equipment prior to leaving incidents in the infested counties have been imposed by California Department of Forestry and Fire Protection and the USDA Forest Service. Equipment cleaning is already required for noxious weed prevention, but it does increase costs and complicates operations.

The federal and state quarantines for coast redwood and Douglas-fir apply only to material less than 1 inch in diameter. Seedling and Christmas trees may be inspected and shipped if they do not have the disease. But there remains the possibility that additional investigations of the disease will find the pathogen in the larger woody portions of the trees and California and the United States will rule that coast redwood and Douglas-fir logs will not be allowed to move outside the 12 infested counties. Canada's regulation currently includes coast redwood and Douglas-fir logs, they may not be imported from California into Canada. This rule is appearing to have no economic impact; there are no reports of coast redwood or Douglas-fir logs moving from California ports directly into Canada. From Seattle, an average of 1.5 million-board feet/year is shipped to Canada (estimated at one barge load). Shipments have been as high as 15 million board feet in 1996 and we do not know if some of those logs originated in California; there is no record of shipments between US ports (Warren 2002).

The longer-term impacts to forestry are harder to predict. We are getting calls from corporate investors in forestlands; clearly they are concerned and worried. While for the most part my replies are reassuring, increased uncertainty discourages investors.

Canada's quarantine does not include lumber and other processed wood products. It is likely that future versions of the United States Department of Agriculture P. ramorum quarantine will exclude lumber so coast redwood and Douglas-fir products could ship freely. If logs were included in the quarantine, there are cases where the logs may be in a regulated county and the mill in an unregulated (uninfested) county, so logs could not be shipped to the mill. It is unclear how significant a problem this may be.

How has sudden oak death impacted commerce and society?

Sudden oak death has captivated coastal California residents. The fear and morbid fascination with sudden oak death has grown as the pathogen was discovered in the UC Botanical Garden, 12 California coastal counties, in Oregon, on coast redwood and Douglas-fir, and as molecular evidence indicates in the foothills of the Sierra Nevada.

Sudden oak death has become part of the California culture. There is a rock band out of Davis called sudden oak death that uses newspaper quotes about the disease in their advertisements. Last month (September 6, 2002), on the front page of the San Francisco Chronicle was a story "Spheres of influence" about the fight over Barry Bond's record-breaking, home run ball. The story set the tone for our current times by saying... "as President Bush lobbies for war and California's redwoods wilt from pestilence."

The scope or reach of the disease has been astounding. The quarantines and our concern were first targeted at coast live oak and tanoak. Neither of these trees is commercial species. There were a few tanoak mills, primarily making tanoak flooring, that closed due to marketing problems unrelated to sudden oak death. One small hardwood mill planned in southwest Oregon did abandon their plans to start-up a pallet manufacturing business due to sudden oak death (personal communication, Jim Lutherland, Rogue Valley Hardwoods).

Phytophthora ramorum doesn't occur on grapevines, but a newspaper story (April 3, 2002, Santa Rosa Press Democrat) on research investigating whether grapes are susceptible and the circumstantial evidence that the coast live oak forests are often adjacent to vineyards in Napa and Sonoma Counties threatened to disrupt agreements between Australia and California for export of grapes to Australia (personal communication, Don Henry, California Department of Food and Agriculture).

Until recently, Canada's P. ramorum quarantine banned the import of all field-grown plants from the entire state of California. Prior to the quarantine, there were millions of dollars worth of plants moving from California to Canada. In addition to ornamental plants, strawberry plants started near Lassen, Tule Lake and other parts of Northern California are shipped to Eastern Canada for a few months and then shipped again to Florida to serve as the basis for Florida's strawberry crop. The strawberry plants were being stopped due to the P. ramorum quarantine, but a special provision was added to Canada's regulation to allow strawberry plants grown in fumigated soil into Canada allowing shipments to resume. Also in September 2002, Canada eased off a bit and set up a certification program for plants from uninfested counties. Plants from uninfested counties may be shipped after soil and plant inspections and laboratory testing. No plants, even non-hosts, can enter Canada from the 12 infested counties. The nursery industry is also on edge since redwood sawdust is commonly used in potting media for container plants.

California bay laurel leaves are used for wreaths and spices. Tanoak and madrone boughs and huckleberry are harvested for florist use. How much material is moving? The Powell River Ranger District in Southern Oregon reported issuing permits for collection of 114,000 lbs of tanoak boughs, 18,000 lbs of huckleberry foliage, and 11,000 lbs of madrone boughs. Flora Pacifica in Harbor, OR, the largest distributor of florist foliage in the west coast purchased over 300,000 lbs of tanoak boughs and 24,000 lbs of California bay laurel (in Oregon called Oregon myrtle). Mary Woodsen, preparing a story for the NY Times in September 2001, estimated 177 tons of regulated articles harvested annually for the North American florist trade. The material is dried for potpourris and spices, or used green in wreaths. Needless to say the Ranger Districts in the quarantine area have suspended issuing such special use permits.

Sudden oak death threatens to disrupt garbage collection. It has been very difficult to effectively quarantine plant debris, branch prunings, grass clippings and other organic yard waste that millions of residents cart to their curbsides, next to their trash. Every working day, arborists, landscapers, utility line clearing crews and others also need to dispose of infested plant materials intermingled with uninfected greenwaste. An estimated three million cubic yards (over 100, 25 ton truckloads a day) of potentially infected organic material is exported from the 12 quarantined counties so it can be utilized and not go to local landfills that are rapidly reaching capacity (Anonymous 2002). To address overburdened landfills, California mandated a 50% landfill diversion in the CA Integrated Waste Management Act of 1989. This Act prompted the segregation of plant materials from other garbage so it could be reused as compost or burned for energy. The regulated articles listed in the quarantine make up 40% of the diverted material and support a $20 million/per year industry of compost and electricity generation. The Phytophthora ramorum quarantine conflicts with the Integrated Waste Management Act since it limits the movement of the diverted greenwaste. It places municipalities in jeopardy, since the maximum penalty for non-compliance with landfill divergence requirements is $10,000 per day.

Complicating the issue further, due to the quarantine, local compost companies in infested counties can't take in plant debris or they would be declared infested and quarantined. At this time, there is no place for tons of greenwaste from the regulated counties to legally go.

A significant amount of Bay Area plant debris goes to co-generation plants throughout the state including one, approximately 30 miles from Yosemite National Park in Tuolumne County. What is the real risk of this material starting a new infestation near Yosemite? We don't have time to go into all the analysis and debate that has gone to settle the issue and a related one on whether composting kills P. ramorum. The scientific data is continuing to be generated primarily from the Garbelotto lab here at UCB and resolution is near. To really understand and predict the risk of the pathogen moving, causing infection and surviving to spread into the forest in the Sierra foothills is difficult. There are many ways to assemble and interpret the data, that allows for those arguing for strict regulation and others trying to show that the risk is low, to both make reasonable arguments. Politics, commercial interests and practical considerations of enforcement also come into play. It makes for excellent intellectual argument and government stalemate and thwarts progress toward a workable quarantine.

These examples touch on how difficult it has been to craft a quarantine to prevent the movement of P. ramorum via commercial trade or other human activities and not also cause unnecessary financial hardship on industries, businesses, and individuals. Quarantines are regulations; they are supposed to be science-based, with enough data to be able to stand up in a court of law if a grower or industry challenges the restriction in court. But how do you base a quarantine on science when you have just discovered a new organism, it doesn't even have a name yet, and experimentation is just beginning? The situation brings into play the "precautionary principle" that states there are circumstances when "precaution" is warranted and quarantines and other natural resource policy may be justified partly on that "precautionary principle". The California Department of Food and Agriculture, which has authority to regulate pathogen movement within the State, did not use the precautionary principle. California tried very hard to make every assertion in the state quarantine be based on science. For example, the state quarantine does not include soil since preliminary data that soil borne inoculum could cause infection in plants was just completed this summer by Jenny Davidson. Now that the research is complete, California is preparing to address soil movement in its quarantine.

All pathogens, not just P. ramorum, are difficult to quarantine. They are not like insects that you can trap, see with the naked eye, and observe that you have killed them. The state and federal governments are still working on the P. ramorum quarantine to agree on one set of rules for people to follow. After more than a year and half of debate we are getting close to a compromise, and to enforceable regulation.

The NY Times on October 5, 2002 ran an editorial on sudden oak death pointing out the economic impacts due to tree loss and quarantine restrictions and the importance of figuring out where the pathogen came from to prevent similar outbreaks. They noted that it's impossible, so far, to know how dire the long-term effects of sudden oak death may turn out to be. The editorial went on to say, ...One of the striking things about the sudden eruption of a pathogen like this is the way it exposes the limits of what we know about the world we live in. It reminds us how recent our scientific awareness of that world really is. Phytophthora ramorum itself is new to science, but it is also occurring in an ecosystem where the basic long-term ecology - the historical view of the ecosystem - is poorly understood because scientists have been investigating it for such a short time. They concluded, "No one knows how woodland and forest ecosystems will ultimately respond to this pathogen's presence. To learn that, we will have to live through it first." But, and note that these are my words, what we as a society do as we live through it are critically important. We need to continue to build the basic understanding of where forest microorganisms are living and their niches in the ecosystem, how they move on commodities and look at limiting global trade in nursery, forest products, and agricultural commodities.

I don't have it all figured out, but the following needs to be discussed more widely and considered. Industries must not look the other way, deny, or cover up insect and pathogen problems as they appear. To ensure that, governments and industries need to provide incentives for growers to be more revealing when they see new pest problems. Insurance funds should be created to compensate growers that are shut down due to new pest outbreaks (currently California has no provisions of this type and federally it takes a special act of Congress and only occurs when large numbers of growers are impacted, such as with citrus canker in Florida).

Several conflicts of interest for regulatory branches of government need to be eliminated. Agriculture Departments have incompatible dual missions: promoting exports and regulating diseases. Finding a pathogen results in adverse impacts to growers and more work for regulatory agencies, so there is a disincentive to find and report new detections.

The regulatory system is complex, requiring cooperation among many agencies and is under funded. Emergency funds should be set up and contracting procedures streamlined so responses to pest outbreaks can be implemented in a timely manner. The regulatory system is designed primarily for agricultural pests in farms and is thin on forestry experience. The California Department of Forestry and Fire Protection only regulates pathogens of commercial species with timber harvest plans, leaving oaks and other trees on private land to be regulated by County Agricultural Commissioners offices, who already are over burdened with West Nile virus, fire ants, glassy-winged sharp shooters, etc. One positive outcome of the P. ramorum quarantine is the forestry and agricultural communities have been compelled to work together.

The concern over sudden oak death has demonstrated that people care about the forests of California and the Nation. There are vast areas of California coastal evergreen forest with a mix of coast live oak, madrone, and bay laurel with little protection other than county ordinances. The forests comprised of non-commercial species are primarily on private lands and regulations are often politically unpopular since they seem to infringe on private property rights. However, as sudden oak death underlines the vulnerability and preciousness of these forests there is a continued fight for strengthening forest policy to sustain these forests for future generations, for wildlife needs, and other ecological concerns.

The California Oak Foundation recently wrote to request that the California Board of Forestry 2003 agenda include updating the Joint Policy on Hardwoods as it pertains to hardwood rangeland issues. They pointed out that new scientific information has been developed since the adoption of the policy in 1994 and note that it does not contain a conservation strategy to address oak ecosystem impacts from sudden oak death.

Others are calling for the closure of all P. ramorum infested public lands. Last year, an environmental impact report for a housing development in Los Angeles County was challenged on the grounds that it did not address the impacts of sudden oak death. Sudden oak death was also used in the fight against the Bahia development in Marin County. Now some are calling for limiting cutting in coast redwood and Douglas-fir forests until the impacts of sudden oak death are fully understood.

Forest and agricultural policy needs to be informed by what we are learning in regards to sudden oak death. If a sustained, strong science-based program for this pathogen is not continued, "fear" will drive forest policy. Is it fair policy for Canada to quarantine desert plants from Southern California for fear of importation of P. ramorum along with cactus? Until Canada had adequate survey data and other information about P. ramorum, it certainly was from their point of view.

When a new damaging pest is found, it is reasonable for regulatory agencies to take a precautionary approach. But, if the void in scientific information is not filled, the new pest can quickly become a pawn to be used for various special interests.

With each mass media story, the "sudden oak death" fear factor is given another boost. To drive future forest policy, we need to increase research, monitoring, education, and management actions so sudden oak death can be fully understood and to limit its spread via human activity. With this understanding of P. ramorum and how it can be managed governments and forest, horticultural and agricultural industries can develop science-based programs that will protect our forests from new invasive pathogens, maintain safe recreation and living spaces, and continue to provide wood products, food, and ornamental plants.

Literature cited

Anonymous. 2002. Sudden Oak Death Syndrome/Oak Mortality Disease. Executive Summary of Solid Waste Industry Needs in California. Prepared by Allied Waste Industries, CA Refuse Removal Council, Waste Management, August 29, 2002. Prepared for USDA-APHIS. Report on file. 7 pgs.

Davidson J.M., Garbelotto, M., Hansen, E.M., Ivors, K., Reeser, P., Rizzo, D.M. 2002a. Another canker-causing Phytophthora from California and Oregon forest trees. Phytopathology (abstract) 92:S17

Davidson, J.M., Rizzo, D.M., Garbelotto, M., Tjosvold, S., and Slaughter, G.W. 2002b. Phytophthora ramorum and Sudden Oak Death in California: II Transmission and Survival. In, Standiford, R.B.; McCreary, D.; Purcell, K.L., technical coordinators. 2002. Proceedings of the fifth symposium on oak woodlands: oaks in California's changing landscape. 2001 October 22-25; San Diego, CA. Gen. Tech. Rep. PSW-GTR-184. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; pgs 741-749.

Garbelotto, M. and Rizzo, D.M. 2002. Report on coast redwood and Douglas-fir as host for Phytophthora ramorum. Report on file. 6 pgs.

Goheen, E. M., Hansen, E. M., Kanaskie, A., McWilliams, M.G., Osterbauer, N. and Sutton, W. 2002. Sudden Oak Death, caused by Phytophthora ramorum, in Oregon. Plant Disease 66:441.

Hansen, E.M., Goheen, D.J, Jules, E. and Ullian, B. 2000. Managing Port-Orford-cedar and the introduced pathogen Phytophthora lateralis. (Feature Article). Plant Disease 84:4-14.

Hansen E.M. and Sutton, W. 2002. Log inoculations to assess tree susceptibility to sudden oak death. Phytopathology (abstract) 92:S33

Kelly, M. and Meentemeyer, R. K. 2002. Landscape dynamics of the spread of Sudden Oak Death. Photogrammetric Engineering and Remote Sensing, 68 (10): 1001-1009.

Rizzo, D. M., Garbelotto M., Davidson J. M., Slaughter G. W. and Koike, S. T. 2002. Phytophthora ramorum as the cause of extensive mortality of Quercus spp. and Lithocarpus densiflorus in California. Plant Disease 86:205-214.

Sinclair, W. A., Lyon, H. H., and Johnson, W. T. 1987. Diseases Caused by Phytophthora Species. In, Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY. Pg. 284.

Swiecki, T.J., and Bernhardt, E. 2002. Evaluation of stem water potential and other tree and stand variables as risk factors for Phytophthora ramorum canker development in coast live oak and tanoak. In, Standiford, R.B., McCreary, D., Purcell, K.L., technical coordinators. 2002. Proceedings of the fifth symposium on oak woodlands: oaks in California's changing landscape. 2001 October 22-25; San Diego, CA. Gen. Tech. Rep. PSW-GTR-184. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; pgs 787 - 797.

Werres S., Marwitz, R., Man in 't Veld, W.A., De Cock, A.W., Bonants, P.J.M., De Weerdt, M., Themann, K., Ilieva, E. and Baayen, R.P. 2001. Phytophthora ramorum sp. nov., a new pathogen on Rhododendron and Viburnum. Mycological Research 105 (10), 1155-1165.

Warren, D.D. 2002. Production, prices, employment, trade in northwest forest industries, all quarters 2000. Resource Bulletin PNW-RB-236. Portland, Oregon. USDA Forest Service, Pacific Northwest Research Station. 171 pgs.


Thanks to Mark Stanley and Katherine Facino, California Department of Forestry and Fire Protection, and to David Rizzo, UC-Davis for continued support and assistance. I also appreciate comments from the following reviewers: Peter Angwin, Everett Hansen, Jonathan Jones, Alan Kanaskie, John Kliejunas, Kathy Kosta, Laura Merrill and John Pronos. Thanks also to Rick Standiford and Larry Ruth at UC-Berkeley, Center for Forestry.

About Susan Jean Frankel

Susan Jean Frankel is a plant pathologist for the USDA Forest Service, Pacific Southwest Region, State and Private Forestry. For over 15 years she has worked on forest diseases in the urban/wildland interface, forest nursery pathogens and forest root diseases. She helped create the California Oak Mortality Task Force to address Sudden Oak Death for the state of California and served as its chairperson for the COMTF's first year. She is currently a Board member of the COMTF and is working in close collaboration with State and local organizations to address Sudden Oak Death for the state and on USDA-Forest Service lands.

Susan has two Masters degrees from the University of Washington, in Forest Pathology (1983) and silviculture in (1990). She has a B.S. degree in Plant Pathology from the University of California, Berkeley (1980).