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Expert doubts oak disease will hit foothills

Scientists are trying to determine whether the fungus-like organism that causes sudden oak death in Northern California trees has reached the foothills of the Sierra Nevada.

A University of California, Berkeley lab is testing leaves found in the foothills last fall for the pathogen that causes sudden oak death.



But a Nevada County expert doubts the disease will ever be a threat here.




“It’s very unlikely that it would ever survive here. It’s too dry. (The disease) likes the moist, coastal conditions,” said Eric Gunderson of the Nevada County Agricultural Commissioner’s office.

“We’ve been looking for it,” Gunderson said, but his office hasn’t seen any sign of it.

Yellowish maple leaves were found in the foothills last fall, but scientists have not matched the DNA taken from the diseased leaves to the pathogen that causes sudden oak death, Phytophthora ramorum, said Matteo Garbelotto, a forest pathologist with the University of California, Berkeley.

“The symptom was similar to what we’ve seen here on the coast, but they’re so generic that it could be anything,” he said. “There’s hundreds of things that could cause a yellow spot.”

Hundreds more samples need to be collected and tested before a match can be confirmed, and that can’t happen until leaves start growing back on the trees, Garbelotto said.

If there is a match, it would be the first one found outside the California and Oregon coastal region. If the pathogen is found in the Sierra Nevada foothills, it’s still unclear if conditions would be right for it to develop into the disease, said Katie Facino, a spokeswoman with the California Department of Forestry and Fire Prevention.

The investigation into whether the foothills have been affected isn’t even as far along as the investigation into whether redwood trees can carry or be affected by the pathogen, Garbelotto said. DNA from Phytophthora ramorum spores has been extracted from coastal redwood sprouts, but conclusive test results have not come in yet to determine whether redwoods can play host to the pathogen.

Scientists are examining samples from trees all over the world for the disease.

Sudden oak death has killed tens of thousands of California’s prized coast live, tan and black oaks. It has also spread to other trees and shrubs, such as bay laurels, rhododendrons, big leaf maples, madrone and manzanita.

Scientists are still learning about the pathogen, which is related to the same type of organism believed to have caused the Irish potato famine in the mid-19th century. No cure has been found and how it spreads is still unclear.


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