Sudden Oak Death (SOD) is found almost exclusively in coastal mixed evergreen and oak woodland forests and also in the urban-wildland interface were natural vegetation remains.
The distribution is patchy. SOD is caused by Phytophthora ramorum, a water mold (a notorious group of pathogens that includes the one that caused the infamous
Irish potato blight in the 19th century). Trees infected with SOD may die within a season or two following their infection. The probable means of contracting SOD are rain-splash, fog-drip, or by wind from a nearby infected plant. Wounds are not necessarily needed for a tree to contract SOD; the pathogen may invade directly through bark. In fact, plant health predisposition may not even play a major role in the tree's susceptibility for SOD.
Movement of wood, leaves, and soil are not recommended since this could spread the infection. There are different symptoms of SOD depending on the species of tree. Spotting, tip die-back, branch and trunk cankers are a few of them. Ambrosia beetles and oak bark beetles are usually associated with infected tan oaks and oak trees. Insecticides may control these beetles but it doesn't prevent SOD. SOD may be prevented, however, with some fungicides. The fungus kills the phloem, cambium and outer xylem, effectively girdling the plant. Because trees killed by SOD are prone to sudden failure and rapid decay, it is wise to remove a tree if it puts people or property in danger. A preventative measure for SOD is to avoid pruning your tree in wet seasons, such as the winter or spring, and also avoid removing dead trees during the months of about November to April, when soils are still wet. Mud from boots, tires, and equipment may also transfer the infection to a new area.
An arborist may have
concerns with a tree infected with SOD, including be the danger of rapid wood decay, wood disposal, dead tree removal, the spread of SOD on vehicles, equipment, boots and tires, and tool disinfection, plus possible therapy and disease prevention.
Alarm regarding the disease has dramatically increased recently after the discovery of finding SOD infecting coast redwood and
Douglas fir trees. Among the list of host plants for SOD are rhododendrons, pacific madrone, big leaf maple,
California bay laurel trees, toyon, native huckleberry, California coffeeberry,
California buckeye, vibarnum, several species of oaks, and several other species.
| For more information on Sudden Oak Death Syndrome, go to the website www.suddenaokdeath.org which provides the latest updates. |
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