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Sudden Oak Death Horticulture

Virtual Oomycyete Demonstration Nursery

Welcome to the Virtual Oomycete Demonstration Nursery

Oomycetes are a group of fungal-like organisms which include important native and exotic plant pathogenic species of Phytophthora and Pythium. These organisms resemble fungi in appearance and behavior but are more closely related to brown algae (e.g. sea kelp). Like brown algae, Oomycetes need water to thrive and disperse. Thus many effective management strategies for Oomycetes in effect restrict their access to water. Keep this in mind as you tour this nursery and see how many of the management practices are essentially moisture management strategies. A second important theme observed throughout this virtual nursery is sanitation.

There are several reasons why it is a good idea to manage against Phytophthora and Pythium species in your nursery. Many of these organisms cause leaf blights and root rots which devalue horticultural merchandise. Some of these organisms are exotic and have the potential to negatively impact our environment by killing and reducing the vigor of trees and other plants that have not evolved defenses against them. Also some of these plant pathogens, including Phytophthora ramorum are regulated by the federal government. If Phytophthora ramorum is detected in your nursery during department of agriculture nursery inspections; mitigation measures will cost your nursery over $12,000 on average in Washington State.

Enjoy your visit and think about how the strategies observed in the WSU Virtual Oomycete Demonstration Nursery could be adapted for your retail or wholesale nursery and even your personal home garden.

Start the tour by clicking on a numbered item on the map below…



Federal regulations for Phytophthora ramorum are developed by the United States Department of Agriculture – Animal and Plant Health Inspection Service. The entire states of California, Oregon, and Washington are regulated to limit the spread of P. ramorum from nurseries. Each state has their own set of regulations.

Click here to see map of quarantine and regulated areas.


APHIS Revises Phytophthora ramorum Domestic Quarantine Regulatory Requirements for Certain Host Nurseries –

As of March 31, 2014, APHIS will no longer impose P. ramorum regulatory requirements for the interstate movement of host nursery stock from certain nurseries located in the regulated areas of California, Oregon, and Washington. Nurseries that have not had P. ramorumdetected in annual surveys since March 31, 2011 will not be required to be inspected and certified in order to ship regulated and associated host plants interstate. Also, nurseries located in regulated areas that do not contain, and that do not ship nursery stock listed as proven host taxa or as associated plant taxa are no longer required to comply with 7CFR 301.92. APHIS will, however, continue to regulate all interstate shipping nurseries located inquarantine areas of California and Oregon, including those that contain only non-host nursery stock.

Read the full document here.


Washington State Department of Agriculture (WSDA)



For Christmas Tree Growers and Forest Managers

Managers, Employees and Volunteers in Public Gardens

Botanical Gardens

Empress 3Because they are open to the public, botanical gardens are at risk of damage from SOD and other diseases and pests. Find out how you can prevent introduction of these organisms and what to do if they get in:

The Sentinel Plant Network

Guidelines for bio-security

These documents from the UK National Trust have information that will also apply to public gardens in the US and Canada:

Guidance for visitors on how to help us protect the garden from introduced pests and diseases

NT Plant Quarantine and Bio-security Guidance Notes

1.Sourcing plants

2a. Handling brought-in plants and quarantine areas – general advice

2b. Handling brought-in plants and quarantine areas – for gardens of significant plant collections and the plant conservation program

3. Use of Phytophthora lateral flow devices (LFD)

4. Cleaning footwear and hands

5. Managing gardens to reduce the risk of pests and diseases

nursery poster english

nursery poster spanish

Now available:

This poster illustrates best management practices for preventing disease and pest problems in gardens and nurseries. It can be posted in a break room or other common area to educate workers, volunteers, and others. Available in English and Spanish versions.

Download the pdf for printing: English or Spanish


Or contact Marianne Elliott to obtain the print version (24″ x 16.5″)

Many thanks to Ian Wright, The National Trust, for providing the information on this webpage.

National Trust is a UK charity formed over 100 years ago to protect places of Historic Interest or Natural Beauty, for ever for everyone.

It now manages 1 million acres of countryside, 600 miles of Coastline, 240 Buildings of Historic importance and 220 historic gardens and parks (covering 35,600 acres in England, Wales and Northern Ireland. The National Trust is financially supported by membership subscriptions, donations and visitor income.

Over 3.5 million people are members of the National Trust. 12 million people visit our gardens each year. Over 700 plants have been raised, bred or named at our gardens. Our gardens span over 700 years of garden history and plant collecting.

Information for Nursery Professionals

Information for Nursery Professionals

Are you interested in keeping Phytophthora ramorum and other diseases out of your nursery?

Here are some resources to help you get started:

Training modules


Best Management Practices Workshop for Nurseries: Steam Sanitation and Disease Identification – February 2016

Información en español


Taller de Mejores Prácticas de Manejo en Viveros : Sanidad con Vapor e Identificación de Enfermedades

Management of P. ramorum in nurseries

We also offer a Critical Control Point assessment, where you will learn best management practices suited to your nursery or garden.

Regulations: State and Federal regulations concerning P. ramorum.

General information for nursery production

Raising and Selling Ornamental Nursery Stock in Washington State by Charles Brun, WSU Extension publication EM102E

Best management Practices Poster:

This poster illustrates best management practices for preventing disease and pest problems in gardens and nurseries. It can be posted in a break room or other common area to educate workers, volunteers, and others. Available in English and Spanish versions. Download the pdf for printing:

nursery poster english


nursery poster spanish


Or contact Marianne Elliott to obtain the print version (24″ x 16.5″)

General Information

General information

Sudden Oak Death

Hosts and identification

Phytophthora diseases

WSU Sudden Oak Death Program

Welcome to the WSU Sudden Oak Death program Website

Some things you will find here:

  • 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

What is Sudden Oak Death? Sudden Oak Death is the common name for a disease caused by Phytophthora ramorum, a non-native plant pathogen. P. ramorum is currently only known to occur in 14 counties in California, a small area in southwestern Oregon and several European countries. P. ramorum has killed hundreds of thousands of oak and tanoak trees in California, and has affected larch plantations in the UK. In Washington and Oregon, P. ramorum is found in mainly ornamental plant nurseries. P. 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.

On this website we provide general BMPs for Phytophthora that can be used on a variety of crops. Other Phytophthora diseases, such as those that cause root disease, can be more damaging than P. ramorum on their hosts.


More reading:


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.

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

Useful links:

Publications available for download


FAQs about Sudden Oak Death

Forest Phytophthoras of the World

Center for Invasive Species Prevention

Contact: Gary Chastagner, 253-445-4528 | WSU Puyallup Research & Extension Center,2606 West Pioneer, Puyallup, WA, 98371-4998 USA
Last updated February 26, 2013


WSU Sudden Oak Death Education Program

With funding provided by the USDA Forest Service and National Plant Diagnostic Network, WSU has developed an education program based at WSU Puyallup which develops educational material and presents workshops and research seminars relating to P. ramorum and other Phytophthora diseases throughout Washington.

WSU provides educational resources for homeowners, Master Gardeners, and nursery professionals such as symptom recognition and early detection of SOD and other Phytophthora diseases. Early detection is key in reducing the risk of widespread outbreaks and protecting Washington’s nursery, landscape, and forest industries from the potentially devastating effects of P. ramorum and other invasive plant diseases.

Best management practices (BMPs) for nurseries are another component of the WSU SOD Education Program. Proper use of BMPs will help nurseries prevent infestation by P. ramorum and other invasive plant diseases, as well as deal with an infestation once it has occurred.

Local students can also get research experience by working on various projects related to Phytophthora.


The Old SOD Blog