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Ornamental Plant Pathology Sudden Oak Death

Sudden Oak Death Research and Education Program


Welcome to the WSU Sudden Oak Death program website. Here you will find information about Sudden Oak Death and other diseases caused by Phytophthora ramorum. We aim to provide resources and services for educators, managers, industries and landowners.  More information about the services we provide are available at the links below.

  • Education– nursery management, symptom identification guides, information for Master Gardeners, events.
  • Research – host testing, fungicide testing, population genetics, disease management.
  • Monitoring – stream monitoring, population genetics of P. ramorum in WA.


Gary leading educational activity


Rhododendron leaves with lesions


Stream baiting for Phytophthora

What is Sudden Oak Death?


Sudden Oak Death is a disease caused by Phytophthora ramorum, a non-native microbe that harms plants (plant pathogen).


Sudden Oak Death has killed hundreds of thousands of oak and tanoak trees in California, and has affected larch plantations in the UK.

Sudden Oak Death


APHIS 2016 SOD Quarantine Map
Areas under active federal quarantine


Phytophthora ramorum has only been recovered from Washington, California, Oregon, several European countries, the United Kingdom, and Vietnam. In Washington and Oregon, P. ramorum is found in mainly ornamental plant nurseries.

Washington State

Phytophthora ramorum has been present in Washington state since 2004, yet no forest outbreaks have occurred as they have in California, Oregon, and the UK. This may not be the case with the next invasive plant pathogen, therefore the use of Best Management Practices (BMPs) for growing clean plants is important for nurseries to adopt.

Best Management Practices


General BMPs for managing Phytophthora on a variety of crops can be found on our website here. These practices are also useful for managing other Phytophthora diseases, such as those that cause root disease, which can be more damaging than P. ramorum on their hosts.

Lifecycle of Phytophthora ramorum

Additional Information and Resources

What’s new:

APHIS Confirms Detection of Phytophthora ramorum-Infected Plants in Commerce 7/10/2019

Are Invasive Plant Pathogens Moving into the Puyallup River Watershed?– A presentation from the Puyallup River Science Symposium 12/7/2018

Critical Control Point assessment for nurseries – find out where the problem areas are and fix them.

More reading:

Let us know if you see broken links or other problems.

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center, 2606 West Pioneer, Puyallup, WA, 98371-4998 USA