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/P. ramorum read more here.

Relatives of P. ramorumother 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.

News

Four eastern U.S. streams positive for P. ramorum in 2023. Read more…

The number of P. ramorum infested sites in England’s and Wales’ larch forests decreased between 2022 and 2023. Read more…

Scotland has updated its P. ramorum Statutory Plant Health Notice map with 2023 results. Read more…

Summary sampling results from CA, OR, and WA nurseries available for 2023. 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.

See more information on increased mortality of Bay Area trees on our new web page, www.bayareatreemortality.org.

Calendar of Events

2023 COMTF and CalPhytos Virtual Annual Meetings: November 7-8, 2023. See the COMTF and CalPhytos agendas. Both the COMTF meeting recording and CalPhtyos meeting recording are now online. 

Recordings of the 2022 COMTF Virtual Annual Meeting: See AGENDA for full details and recordings from each day below.

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.