Sudden Oak Death is a tree disease caused by the fungus-like plant pathogen Phytophthora ramorum. First recognized in the mid 1990s, the disease kills some oak species (primarily coast live oak, Quercus agrifolia, and an oak relative, tanoak, Notholithocarpus densiflorus) and has had devastating effects on coastal forests in California and Oregon. The pathogen also infects rhododendrons, camellias, and other common horticultural plants, causing ramorum blight. In the UK and Ireland, the pathogen is causing extensive damage on Japanese larch (Larix kaempferi) in plantations.

Phytophthora ramorum was inadvertently introduced to California forests on nursery stock and, as an invasive species, is quarantined in over 60 countries with restrictions enforced on shipments of nursery stock and other host plant materials. For an introduction and background on Sudden Oak Death/Phytophthora ramorum read more here.

Relatives of P. ramorum, other Phytophthora species are damaging native and ornamental vegetation throughout California. Unintentional pathogen introductions are an acute concern for restoration of sensitive habitat where restoration nursery stock may serve as a pathway for pathogen introduction into rare, threatened or endangered species habitat. Read more about other Phytophthora species found in native habitats, native plant nurseries, and restoration sites here.


A forest health information workshop for the north coast, including information on sudden oak death, will be held in Eureka late this winter or early spring. Check our calendar or for more details as they become available.

Thirty-six new P. ramorum detections in Oregon in 2017, including seven sites with the EU1 strain. Read more…

No P. ramorum recovered from fall 2017 samples of the Kitsap County Botanical Garden in Washington. Read more… and view a video chronicle of the story produced by Washington State University Extension.

Pencils made from a tanoak tree that had sudden oak death were featured at the opening of a School of the Art Institute of Chicago and University of Chicago art exhibit in Cleveland, Ohio in December 2017. Read more…

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Calendar of Events

2/1 – 2/3 – 2018 California Native Plant Society Conservation Conference;
Los Angeles, CA

View more details on upcoming events in the latest newsletter…




Help stop the spread of forest pests – including Sudden Oak Death – on firewood! Check out the website of the California Firewood Task Force.

The California Oak Mortality Task Force is a task force under the California Forest Pest Council.