Researchers probe spread of Sudden Oak Death

By Robert Sanders, Public Affairs

16 January 2002 | Sudden Oak Death, the disease that has killed trees up and down the Pacific Coast, has likely invaded much of the East Bay, if the recent discovery of its spread across campus is any indication.

“I don’t think it has been around the East Bay for a long time, but long enough to spread,” said Matteo Garbelotto, a leading researcher in Sudden Oak Death and a forest pathologist at the College of Natural Resources. “The Berkeley campus isn’t an island, so if it’s here, it’s probably all around us, and we just haven’t noticed it yet.”

Last fall, Garbelotto noticed yellowed leaves on some California bay laurels and a California buckeye on the campus and, after DNA tests, confirmed the presence of Sudden Oak Death. A more complete survey of the campus in November turned up 34 infected trees and shrubs, including some at the world-renowned UC Botanical Garden.

No treatment or cure for the disease is known. Garbelotto is at the forefront of research to understand the disease and its host range, and to find effective treatments.

“What we discover on the campus is going to advance our scientific understanding of the disease, determine the disease’s host range, and hopefully come up with a way to control it,” said Garbelotto, an adjunct professor in the environmental science, policy and management department.

On campus, the trunks and lower limbs of all oak trees in the known infected areas are being coated with a pesticide, copper sulphate, that Garbelotto found could prevent the microbe from entering the oak. Yellow flags around trees indicate that they have recently been treated with copper sulfate — not that infection has been found.

The campus has alerted the city of Berkeley and the East Bay Regional Parks that the disease could be elsewhere in the East Bay. Once the campus survey confirmed Sudden Oak Death in the UC Botanical Garden, garden director Ellen Simms immediately instituted a quarantine on all plants and plant parts, stopping distribution to scientists and arboretums and suspending the sale of plants to the public.

“The UC Botanical Garden is a museum of living plants, one of the most diverse botanical gardens in the country,” said Simms, an associate professor of integrative biology. “Sudden Oak Death could profoundly affect the garden and its scientific mission.”

Simms said the garden now has an important scientific role to play in clarifying the host range of the microbe responsible for the disease.

While some hosts are very efficient at transmitting the pathogen, others appear unable to do so. Research at the garden can determine which hosts are poor transmitters of the disease — which should help limit the plants destroyed in eradication efforts.

“Knowing the host range will also help to narrow the import restrictions that are being placed on California plant and wood products by other states and countries,” said Simms.

The campus survey turned up potential new hosts, including the coast redwood. The pathogen was found on dying shoots at the base of a redwood. More tests must be done to determine whether the pathogen affects mature trees.

Information on Sudden Oak Disease on campus is available at www.cnr.berkeley.edu/SOD. For information on recognizing and managing the infection, see www.suddenoakdeath.org or camfer.cnr.berkeley.edu/oaks.