Sudden Oak Death
First
observed in the early to mid-1990s, Sudden Oak Death (SOD) was initially seen as
the quick appearance of a sickly tree, followed by the tree’s death within a
year or so thereafter. The hardest hit trees were the tanoaks, and the trees
often died in groups, slowly spreading across a hillside. The culprit was found
to be the water mold Phytophthora ramorum, which has caused substantial
mortality in tanoak trees and several other oak tree species (coast live oak,
California black oak, Shreve oak, and canyon live oak). The pathogen also can
cause twig and foliar diseases in other plant including California bay laurel as
well as two trees which are the mainstay of the California Coastal timber
industry, Douglas-fir and coast redwood. P. ramorum thrives in cool, wet
climates typical of our coastal evergreen forests that lie within the fog belt.
Research in California forests has shown that the greatest predictor of P.
ramorum is the presence of California bay laurel (Umbellularia
californica).
Nurseries in drier areas can create moist habitats to cultivate their sale stock, and these microclimates may create an environment that allows P. ramoru to spread far from the coast. The water mold has affected nursery stock in both in the United States and Europe, where the pathogen infects the leaves and twigs of several common ornamental nursery plants, such as rhododendrons and camellias, which then serve as vectors for pathogen dispersal.
A California Oak Mortality Task Force (COMTF) was formed in 2000 to focus on the SOD pathogen which has been estimated to have killed over a million native oak and tanoak trees in 14 coastal California counties and Curry County, Oregon. Two separate state organizations--the California Forest Pest Council (CFPC) and the California Department of Forestry and Fire Protection (CDF)--formed a coalition of research/educational institutions, public agencies, non-profit organizations, and private interests with the goal of coordinating research, management, monitoring, education, and public policy efforts relating to SOD. Further information about SOD can be found at the COMTF website: nature.berkeley.edu/comtf
The NCRCDC has sponsored numerous Sudden Oak Death workshops aimed at educating landowners in the identification and control of SOD. In addition, the NCRCDC has coordinated with the University of California to provide technical support information to coastal counties for use in their local education efforts for reducing the spread of SOD. The NCRCDC is available for providing technical support regarding SOD to local governments, tribes, landowners and interested individuals.