Sudden Oak Death (or SOD) is a very real danger facing Oaks and other trees that can be carriers of SOD in parts of the Bay Area.
"Since the mid 1990s, P. ramorum has caused substantial mortality in tanoak trees and several oak tree species (coast live oak, California black oak, Shreve oak, and canyon live oak), as well as twig and foliar diseases in numerous other plant species, including California bay laurel, Douglas-fir, and coast redwood. The pathogen was also discovered in European nurseries in the mid 1990s, and it has since spread to wildland trees in the U.K. and the Netherlands. Although the first P. ramorum-infested California nursery stock was identified in 2001 (Santa Cruz County), the U.S. nursery industry was not widely impacted by the disease until 2003, when the pathogen was detected in California, Oregon, Washington, and British Columbia nurseries. "
http://www.suddenoakdeath.org/html/history___background.html
For more information, please check out this link:
http://www.plantmanagementnetwork.org/php/shared/sod/
