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Local oak trees avoid disease outbreak


Photo By: Ellie Van Houtte/ Town Crier
Photo Ellie Van Houtte/ Town Crier A UC Berkeley researcher demonstrates how to prepare a treatment for protecting oak trees from Sudden Oak Death at Foothills Park in Los Altos Hills.

Local residents gathered at Foothills Park in Los Altos Hills Saturday to learn how to treat and protect oak trees from Sudden Oak Death, a crippling pathogenic infection that threatens to eradicate 90 percent of California’s black oak and live trees within 25 years, according to researchers at UC Berkeley.

Although the spread of Sudden Oak Death has largely circumvented Los Altos and Los Altos Hills, 17 infected trees were discovered during this year’s Sudden Oak Death Blitz, an onsite survey conducted in May. Results of the Blitz revealed that nearly 10 times more trees were infected with the disease in 2012 than in the previous year.

A series of wet winters that opened into mild spring temperatures created the perfect storm for the disease to take hold. Of the 12 areas tested during the Blitz, the East Bay, Saratoga and Sonoma recorded the highest numbers of infected trees.

Sudden Oak Death emerged in California less than 25 years ago when infected California Bay Laurels and other ornamental plants were introduced into the local landscape. Although bay laurels can harbor the disease without dying, oak trees contract the virus through the pathogens of infected plants, soil, water or garden tools – and suffer an inevitable death.

“It’s sort of like a cancer diagnosis,” said Sue Welch, member of the Los Altos Hills Open Space Committee and Blitz volunteer. “You want to catch (the disease) beforehand. … If you catch the tree after it’s infected, there’s not much you can do.”

During the 2012 Blitz, 35 volunteers surveyed 511 trees in Los Altos and Los Altos Hills and collected leaf samples from 137 bay trees suspected of carrying the disease.

In addition to Byrne Preserve, where 35 diseased oak trees were removed two years ago, Juan Prado Mesa Preserve and the Matadero Creek area are hot spots for the disease in Los Altos Hills, according to Welch.

Fewer cases of the disease have appeared in Los Altos, with none identified in Shoup Park, Redwood Grove or Heritage Oaks Park over the past four years.

Welch attributed the low incidence of Sudden Oak Death in Los Altos and Los Altos Hills to the area’s residential, landscaped nature and the presence of less native vegetation than in undeveloped areas.

Infected trees and oak trees not yet infected can be treated with an annual injection or bark application of phosphite, a chemical treatment with minimal environmental impact that increases a tree’s resistance to the disease.

Experts at UC Berkley encourage residents to stop the human-induced spread of Sudden Oak Death by buying ornamental plants from nurseries that test for the disease, isolating wood from infected trees and cleaning garden tools and vehicles of all debris and soil collected in locations near infected plants and trees.

For more information on Sudden Oak Death, visit cnr.berkeley.edu/garbelotto or sodblitz.org.

For the Town Crier's full album of photos illustrating the symptoms of infected oak trees as well as treatment methods, click here.

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