Campus: Sonoma State University -- December 22, 2000

SSU Biologists Tracking Early Signs of Sudden Oak Death

Biology professors from Sonoma State University are tracking early signs of Sudden Oak Death Syndrome in trees at its research facility, the 210-acre Fairfield Osborn Preserve. They now say "the disease has probably already progressed to an alarming degree within the Preserve's boundaries."

How the study of the stages of early infection of Sudden Oak Death in Sonoma County can help researchers tackle this critical problem throughout California will be one of the topics of an important symposium on January 15.

Sonoma State University biology professor Nathan Rank and Fairfield Osborn Preserve Manager Julia Clothier are organizing a meeting between CSU faculty and students, members of the UC task force researching Sudden Oak Death syndrome, local interested biologists and preserve managers.

They hope to combine research efforts and develop a strategy to understand how the disease is spread. The all-day meeting is scheduled at the Double Tree Hotel in Rohnert Park. Information is available at

The deadly fungus has now been reported in Sonoma County in Jack London State Park, Kings Ridge, Austin Creek State Recreation Area, Sugarloaf State Park, along Bodega Highway, and Cazadero, according to the UC Davis web site at

Northern Californians have witnessed a dramatic die-off of oak trees in coastal woodlands surrounding the Bay Area in recent years. Entire stands of oaks have succumbed in some areas. Tan oaks and coast live oaks have suffered the highest levels of mortality, but some black oaks have been affected, said Rank. There is no known cure for the disease.

The Preserve, located east of the campus in Penngrove, is an educational resource for the community at large and an educational and research facility for the University.

Thousands of school children visit the Preserve every year on guided tours, and members of the public participate in organized weekend hikes and field workshops in the fall and spring.

"We don't know yet whether oaks on Sonoma Mountain will suffer a massive die-off," said Preserve Director Nathan Rank, a biology professor. "But the disease may be spreading more slowly at the Preserve than other locales it has surfaced in," Rank added.

"It may be that temperature is the reason," Rank said. "The Preserve has a warmer microclimate than most of Marin County where the fungal disease has effectively decimated the oak population in many areas."

SSU students visit the Preserve to learn about its ecology, natural history, archaeology, geology, and geography as part of their coursework. Scientists at SSU and the surrounding area also use the preserve as a natural laboratory for studying ecological processes.

"The presence of the disease at a nature preserve where biologists are already actively researching oak ecology presents an opportunity for study, and we hope, for control," said Rank who is spearheading the effort with his colleagues Dr. Hall Cushman and Julia Clothier, Preserve Manager.

During the summer, scientists at UC Davis, led by Dr. David Rizzo, identified the disease-causing agent as a fungus that is closely related to another fungus that kills Port Orford Cedar in southern Oregon. It is more distantly related to the fungus that caused Potato Blight and caused massive starvation in Ireland in the mid-19th century.

Over the past year, Clothier had noticed the leaf canopies on several coast live oak trees near the Preserve's Education Center were turning brown. This fall, Rizzo and his co-workers isolated the fungus from several Preserve coast live oak trees that showed symptoms of Sudden Oak Death.

These findings prompted SSU faculty members to organize a survey of the Preserve with Clothier, Preserve volunteers, several graduate students and undergraduate volunteers.

SSU students used the Department of Biology's state-of-the-art Global Positioning System units to determine exact locations of diseased trees in the oak survey. These locations will be later used for geographic modeling of disease occurrence and spread.

Rank reported that more than sixty trees possessed active or recently dried bleeding spots, which are characteristic of early stages of the disease. Twenty trees showed evidence of crown death, and damage from bark beetles associated with late stages of the disease was noted on a number of trees.

Afflicted trees can be found throughout the Preserve, but Rank said most trees still show no signs of being affected by the disease, and there is as yet "little evidence of widespread crown death or wholesale tree death in Preserve oaks."

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