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UC works to curb ‘sudden death’ of California’s majestic oak trees

Dead and dying oaks create an ominous landscape in California coastal areas stricken by the recently introduced disease ‘sudden oak death.’ No treatment or cure for the disease is known, however, UC scientists are at the forefront of research to understand the disease and its host range, and to find effective treatments

Since it was first observed in 1995 in Marin County, sudden oak death has killed tens of thousands of coast live oaks, black oaks, Shreve oaks, and tanoaks from California’s central coast to southern Oregon. The disease is widespread on the UC Berkeley campus.

Public safety, environmental, and economic consequences of the disease are growing. Dead trees have come crashing down on campsites, spurring the closure of China Camp State Park in central Marin County and removal of hazardous trees to prevent injury to people. In addition to being an eyesore, the dead trees are a fire hazard.

UC scientists identified the fungus-like pathogen that is killing the oaks as a new species of Phytophthora, named Phytophthora ramorum. (Another species of Phytophthora was responsible for killing Ireland’s entire 1846 potato crop.) So far, it has been found to infect at least 15 different plant species, though it apparently does not kill plants in all of those species. Two hosts, rhododendron and bay, are thought to be the most problematic in terms of spreading the disease, according to UC scientists. The pathogen can produce spores on them year-round. Many parks have asked hikers to clean soil from their shoes and bicyclists to clean their tires to prevent spreading the spores.

The California Oak Mortality Task Force, a non-profit organization formed in August 2000, brings together UC scientists, public agencies, and other organizations to address the issues accompanying sudden oak death. The task force is implementing a comprehensive and unified approach for research, management, education, and public policy. For more information, see the California Oak Mortality Task Force Web site at http://www.suddenoakdeath.org.

A peer-reviewed scientific paper on Phytophthora ramorum and extensive oak mortality in California has been published in the March 2002 issue of the journal “Plant Disease.” The citation is Rizzo, D. M., M. Garbelotto, J. M. Davidson, G. W. Slaughter, and S. T. Koike. 2002. Phytophthora ramorum as the cause of extensive mortality of Quercus spp. and Lithocarpus densiflorus in California. 86: 205-214. The abstract is on the Plant Disease Web site. (http://www.apsnet.org/pd/current/top.asp)

Background information on SOD and photographs are available on the UC ANR News and Information SOD online media kit. (http://danr.ucop.edu//news/MediaKit/SOD.html)

(March 2002)

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