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.


Two WA waterways found positive for P. ramorum in 2017 sampling. Read more…

More positive confirmations from Oregon’s forests, including EU1 lineage. Read more…

Lookalike symptoms on CA bay laurel leaves confirmed to be caused by Diplodia corticola, pathogen on oaks and grapevines. Read more…

Spring 2018 SOD Blitz season begins in March! Read more… and see the Calendar of Events

The Phytophthoras in Native Habitats Work Group officially joins COMTF as the “Other Phytophthoras” Committee. Read more…

Read 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.

Calendar of Events

3/22 Managing Uncertainty: Sudden Oak Death and Other Pests, Fire, and Drought workshop; Humboldt County, CA

3/30 – Mendocino County SOD Blitz

4/7 – Carmel Valley Village SOD Blitz

4/7 – Santa Lucia Preserve SOD Blitz

4/14 – South Skyline SOD Blitz

4/14 – Saratoga and Midpeninsula Regional Open Space District SOD Blitz

4/17 Free Arborist, Tree Care Specialist, and Urban Forester Spring Sudden Oak Death Training; Santa Rosa, CA

4/18 – Santa Cruz SOD Blitz

4/19 – Free Phytophthoras in Native Habitats Work Group field trip to tour US Forest Service Nursery;  Placerville, CA

View more details on upcoming events in the latest newsletter…

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