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UC Berkeley officials taking action to halt spread of tree-killing pathogen found on campus
31 October 2001

By Sarah Yang, Media Relations

Berkeley - A pathogen that has devastated wide swaths of California's oak trees has been discovered on the grounds of the University of California, Berkeley, leading campus officials to take aggressive steps to contain its spread and protect the landscape.

The microbe responsible for Sudden Oak Death has infected three host species, including two California bay trees near Faculty Glade. The infection has not been detected in any of the oak trees on campus, suggesting the disease has only recently arrived.

Approximately 50 campus groundskeepers, gardeners, arborists and horticulturists from UC Berkeley's Botanical Garden received training this morning (Wednesday, Oct. 31) to learn how to identify signs of infection. Over the next two weeks they will canvass the campus and gather samples of suspicious vegetation. Disease management will be based upon the results of the survey and will include regular monitoring of the campus grounds. Areas surrounding the campus also will be surveyed through a joint effort between UC Berkeley and the Alameda County Agricultural Commission.

"We need to act quickly before the pathogen spreads," said Jim Horner, landscape architect for UC Berkeley. "Our goal is to take action before the winter rains hit, because that's the time when spores may spread more easily to oak trees by splashing off the leaves of infected trees or through tracking of wet soil."

Matteo Garbelotto, a leading researcher in Sudden Oak Death and a forest pathologist at UC Berkeley's College of Natural Resources, noticed the infections while walking through campus. Subsequent tests confirmed the infections were caused by Phytophthora ramorum, the invasive microbe that causes Sudden Oak Death.

Horner and Garbelotto are leading the effort to protect the hundreds of species of trees and plants on university grounds. Many of the trees on campus date back to the 1870s, and a few of the oak trees are more than 200 years old.

There are at least 10 known tree and plant species that are susceptible to the P. ramorum pathogen. The highly contagious microbe is a brown algae related to the species responsible for Ireland's potato famine of the mid-1800s. Its ability to infect a wide array of plant life through soil, water and air has made it particularly difficult to control.

"Within this genus, there is nothing else that can spread the way this pathogen can," said Garbelotto, who is also adjunct professor in the Department of Environmental Science, Policy & Management. "We're only beginning to understand how it spreads, and how it might be stopped."

Sudden Oak Death was first noticed in Marin County in 1995 and has since felled tens of thousands of coast live oaks, black oaks and tan oaks in the state. Infections have recently been discovered along Crow Canyon Road in Alameda County and near Lake Madigan in Solano County.

Earlier this year, Garbelotto and David Rizzo, an assistant professor of plant pathology at UC Davis, found that the tree-killing microbe has also infected rhododendrons in Germany and the Netherlands.

UC Berkeley will be coordinating plans with state and local officials to begin limited treatment of the infected areas on campus.

Garbelotto has tested chemical treatments on hundreds of potted oak trees infected with P. ramorum. He found that phosphites injected through small drilled holes in the tree slowed the growth four-fold and significantly reduced the appearance of lesions.

He also found that coating the trunk of the tree with copper sulfate could prevent the microbe from entering the oak. The preventive treatment may be used for the oak trees near the known points of infection on campus.

The UC Berkeley Office of Environment, Health & Safety is devising safeguards to minimize any human and ecological risks from use of the chemical treatments. Treatments will be minimized and limited to situations where they will have the highest likelihood of slowing or containing the infection.

To help prevent the spread of the pathogen on campus, informational signs will be put up and foot traffic prohibited around the infected areas.

"Much of this is a work in progress," said Garbelotto. "Because Sudden Oak Death is such a new disease, there is no treatment officially approved for the pathogen. Our hope is that the information we gain by using these treatments here will not only help preserve the landscape on campus, it will help save trees and plants beyond UC Berkeley."

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