Sarah Yang, Media Relations
- 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
"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
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
To help prevent the spread of the pathogen on campus, informational
signs will be put up and foot traffic prohibited around the infected
"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."