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…

Regulations

Federal regulations for Phytophthora ramorum are developed by the United States Department of Agriculture – Animal and Plant Health Inspection Service.

Distribution

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.

The entire state of California and one county in Oregon (Curry) are under quarantine.

Click here to see map of quarantine and regulated areas.

Important Updates

3/31/14

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. ramorum detected 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.

Resources

State

• Washington State Department of Agriculture (WSDA)
• California Department of Food and Agriculture (CDFA)
• Oregon Department of Agriculture (ODA)

Federal

• USDA-APHIS Plant Pest and Disease Programs
  • Phytophthora ramorum (Webpage)
    • Regulations
      • Federal Regulations, 7 CFR 301.92 – 301.92-12 (Webpage)
      • Federal Orders (Webpage)
    • Management
      • Manual (PDF)
      • Host List (PDF – May 2020)

• A Christmas Tree Grower’s Guide to Phytophthora ramorum (COMTF Nov. 2006)
• P. ramorum Guide for Forest Managers, Christmas Tree Growers, and Forest-Tree Nursery Operators (OSU Extension April 2006)
• Photo gallery of P. ramorum symptoms on conifers (under construction)

Because 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

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.