Sudden Oak Death

Thanks to The Voltage Gate, the host of Oekologie #5, here is a link to a video that explains the status of Sudden Oak Death (SOD) in California.

SOD is a devastating disease of oak, caused by Phytophthora ramorum, a member of the Oomycota, briefly described in a previous post. Initially reported in Central California in 1995, P. ramorum has been found in Oregon, Washington, New Mexico, Texas, Colorado, Arkansas, Alabama, Louisiana, and as far East as Tennesee, Virginia, North Carolina, South Carolina, Virginia, Florida, and Georgia [SPDN]. P. ramorum has a wide host range (the disease can infect many different plant species). Some other hosts of the pathogen may not show symptoms, which makes it easier for the disease to spread.

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In some areas of California, 90% of the Oak trees are affected, and once symptoms appear, the tree often dies within a year a two. Phosphonates (or phosphites) are chemical compounds that can be used to treat plants infected with members of the Oomycota, and seem to be fairly effective against SOD. The treatment of full-grown trees, however, is difficult and expensive, so it is not very practical to treat large numbers of trees.

The spores of the pathogen are spread in wood, or by rain splash.

List of useful websites:
California Department of Food & Agriculture SOD Quarantine information
California Oak Mortality Task Force
The Southern Diagnostic Plant Network SOD webpage
USDA-APHIS SOD website
USDA-Forest Service Pest Alert
American Phytopathological Society News & Views