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Surge in sudden oak death comes to Portola Valley, Woodside
• Wet spring followed by hot summer are culprits.

by David Boyce

The extended wet spring of 2005-06 and the dry hot summer that followed has caused a spike in the number of trees in Portola Valley and Woodside afflicted with sudden oak death, a pathogen that is particularly deadly to tan oaks, coast live oaks and black oaks, in that order.

Since January 2006, the San Mateo County Department of Agriculture, based on concerned calls from residents, has identified four new locations of the disease in Portola Valley and six new sites in Woodside, said Gail M. Raabe, the county's commissioner of agriculture.

Marge DeStaebler, of Portola Valley's Conservation Committee, said she's lost three live oaks to the disease since 2005 at her Santa Maria Avenue home. She had her trees analyzed by a private lab in San Jose.

The committee published a warning about the disease on April 26 on the town's Web site at portolavalley.net. The warning is based on an earlier March 1 statement that was "fleshed out" by committee member Derry Kabcenell, who learned of infected trees on his property near the Windy Hill Open Space preserve, Ms. DeStaebler said.

The combination of moisture followed by warmth is perfect for this pathogen, said Katie Palmieri, the spokeswoman for the California Oak Mortality Task Force, an offshoot of the California Forest Pest Council, a nonprofit educational and advisory group on forest health.

"You get a couple of years of backlash of spore build up" with a wet spring and hot summer, she said. "The more taxing of a summer, the more dramatic the symptoms."

There is no cure, but a certified arborist can protect healthy trees and those with very early infections, Ms. Palmieri said.

The disease has many native carriers, particularly bay laurel trees, camellias and rhododendrons, she said. It also spreads via wood chips that haven't been sufficiently dried, gardening tools that haven't been sanitized with bleach, wind and surfaces such as shoes, paws, hooves and tires.

Most of the new Portola Valley sites noted by the county are in the upper reaches of Alpine Road. Proximity to open space is the most common factor in the spread of the disease, Ms. Palmieri said. "San Mateo County is not one of those counties where it's totally taken over," she added.

INFORMATION

For a free biological analysis of a suspected tree, call the San Mateo County Department of Agriculture at 363-4700.