Stalking Sudden Oak Death
Grounds crews ramp up efforts to spot signs of tree-killing pathogen

By Sarah Yang, Public Affairs

During a walk-through in Faculty Glade, forest pathologist Matteo Garbelotto, right, examines a leaf with Richard Orlando, lead gardener at Clark Kerr campus. Tree crew lead Richard Trout, center, looks on. Peg Skorpinski photo

07 November 2001 | A pathogen that has devastated wide swaths of California’s oak trees has been discovered on campus, prompting 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 the UC Botanical Garden received training last Wednesday on how to identify signs of infection. This week and next, they are canvassing the campus and gathering samples of suspicious vegetation.

Disease management will be based on results of the survey and will include regular monitoring of the campus grounds. Areas surrounding the campus will be surveyed through a joint effort between the campus and the Alameda County Agricultural Commission.

“We need to act quickly before the pathogen spreads,” said Landscape Architect Jim Horner. “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.”

An aggressive pathogen
Matteo Garbelotto, a leading researcher in Sudden Oak Death and a forest pathologist at the 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 an 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.

At least 10 known tree and plant species 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 and 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.

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

Research in progress
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 Office of Environment, Health and 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 path-ogen. 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.”

For information on recognizing and managing Sudden Oak Death
infection, see suddenoakdeath.org or camfer.cnr.berkeley.edu/oaks.