Name

Its official name is Phytophthora ramorum. There is a second fungus which can also cause SOD -- Phytophthora nemorosa.

History

The fungus (or water mold) was first detected in California 1995 in Monterey, Santa Cruz and Marin Counties. It may have originated in Europe. It has killed more than 1,000 Tanoaks in Big Sur. It was identified as a previously unknown forest pathogen in 2000. 

Quarantined
In 2001, Canada, South Korea, and Oregon issued quarantines on California SOD forest products. The United Kingdom joins the quarantine in 2001, as does the Czech Republic in 2003. In 2003 the European strain was found in America and vice versa.

In 2003? a California quarantine was ordered, intended to prevent moving potentially affected trees, parts  and seedlings out of counties, including Monterey County, known to harbor the disease. 

Affected Species Breadth

SOD has been found in 38 tree and plant species including Tan Oak (Lithocarpus densiflora), Coast Live Oak (Quercus agrifolia), Huckelberry, Bay Laurel, Madrone (Arbutus menziesii), Buckeye (Aesculus californica), Manzanita (Arctostaphylos manzanita), Big Leaf Maple (Acer macrophyllum), and California Rhodededenron (Rhododendron spp), Douglas Fir (Pseudotsuga menziesii v.menziesii) and Coast Redwood (Sequoia sempervirens). An additional 16 tree and plant species host the fungus but are not known to be susceptible to it.

Mapping

SOD has been found in 12 California counties, primarily within 15 miles of the coast and most occurrences are near the San Francisco Bay area. It has been found from Gorda in Big Sur in Monterey County to Southern Oregon. It has been found in nurseries as far north as Washington State and more than 100 miles inland in Placer County. 

Symptoms

It is very difficult to see if trees are infected until they are dead. Infected trees do bleed sap similar to pine resin. Infections can occur on the trunk, branches, or leaves. Cankers on the trunk are most damaging.

Mortality vs. Symptoms

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Susceptibility v. Resistance

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Spread

The Big Sur outbreak is considered the worst in the state. It is spread through rain splash and human transport of infected plant materials.

Strains (or VCGs)

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Cures, Treatments

There is no known cure or treatment, although the systemic fungicide AGRI-FOS(R) and Pentra Bark surfactant were approved in 2003 by the California Department of Pesticide Regulation (DPR) to treat individual oak and tanoak trees at high-risk of contracting Phytophthora ramorum.