| Sudden oak death |
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| Phytopthora ramorum |
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Plant hosts
View a complete list provided by USDA APHIS. (pdf 4 KB)
To view larger image click on picture.
Image provided by Joseph O'Brien, USDA Forest Service.
Means of movement and dispersal
Natural dispersal of P. ramorum is by drifting plant material, waterborn and soilborn chlamydospores, and by waterborn, soilborn and possibly airborn sporangia. There are no known vectors of the disease other than man. P. ramorum has been proven to be effectively moved through the trade of ornamental plants and green waste. There is evidence that mature compost will not be infectious.
Symptoms
Phytopthora ramorum causes different symptoms on different hosts. 'Sudden oak death' on tree species is characterized by 'bleeding' cankers that girdle the trunk of tanoaks and some other oak species. On Rhododendron, Pieris, Viburnum, Camellia and Vaccinium ovatum, the disease is characterized by leaf blights and shoot diebacks. Shoot dieback occurs when disease is severe. On Viburnum, infected leaves may die and fall off, leaving dark, leafless stems. In more severe infections, Virburnum can be killed. On Pieris, infected leaves turn a dark brown. Young shoots and leaves are very susceptible to infection. Other hosts such as camellia may be infected but have only subtle symptoms, such as small leaf lesions on the lower leaves. Infected leaves on these hosts often fall off.
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