What is it?

Sudden Oak Death, also referred to as SOD, is caused by the oomycete plant pathogen Phytophthora ramorum. The pathogen can kill a variety of oak species and can sicken other varieties of plants including the rhododendron and the huckleberry.

What are the symptoms of SOD?

-Dark sap “bleeding” from the base of the tree (see picture to the right)

-Leaves rapidly change from green to brown

-Fine dust from beetles boring through the bark and the wood

The above are just symptoms and can be associated with other tree diseases. The only way to be sure a tree is infected is by culturing the pathogen in lab. Also, the above symptoms are those found with species of oaks with the disease. Symptoms for other species of plants and trees may vary. View list of SOD host plants.

Where is it?

It seems the plant pathogen is localized to central coastal California but has also been confirmed in southern Oregon. A similar species has also been discovered in the UK and Europe.

Phytophthora ramorum may be influenced by climate including humidity and temperature which may prevent oaks in southern California from becoming infected.

How is passed from tree to tree?

It is not known how the pathogen is spread but there is some speculation. Other species of  Phytophthora are transmitted via air and water but many researchers think the pathogen for SOD can be carried on shoes, by pets and even vehicles. Commercial nurseries may also be a source transmission.

How can it be prevented?

Isolating any known infected areas is crucial to control. Be sure to clean your feet, your pet’s feet, camping gear, tools, etc… when moving from an area known to have the pathogen to an area that is not infected.

Also, minimizing damage to the tree trunk and large branches as well as pruning only during dry summer months when beetles and pathogens are least active can make the tree less susceptible.

How to treat it?

There is no known control for SOD. While some treatments are being used and showing slight signs of effectiveness, there isn’t a proven treatment. There is hope as other species of Phytophthora have been controlled with various fungicides.

This is just a brief overview of sudden oak death. For more information, refer to any of the credible resources below.

California Oak Mortality Task Force

Washington State Department of Agriculture – Sudden Oak Death

University of California  – Sudden Oak Death in California

Related posts:

1. Carpet Beetles of California We’ve talked about a lot of pests on this blog...
2. Are There Brown Recluse Spiders in California? Sorry for the short hiatus (okay several months) but...
3. The Mediterranean Fruit Fly – Another Costly Agricultural Pest The state of California is known for its agriculture;...
4. Weird Insects: the Artichoke Plume Moth The artichoke plume moth is a moth (believe it...
5. Hantavirus (HPS): a Potentially Deadly Virus Carried by Rodents Hantavirus or hantavirus pulmonary syndrome (HPS) is a virus...

Related posts brought to you by Yet Another Related Posts Plugin.