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Phytophthora ramorum

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Phytophthora ramorum is an invasive plant pathogen that causes sudden oak death,

ramorum blight, ramorum dieback, and Phytophthora canker diseases. There is no

cure for the diseases caused by P. ramorum. Preventing the movement of infected

plants and materials is the best way to protect our forests and landscape plants.
The water mold, P. ramorum, is an invasive pathogen that can infect over 100 plant

species (319.67 KB). In coastal California and southern Oregon, P. ramorum causes

sudden oak death, a disease which has killed millions of trees, primarily tanoak and

coast live oak. The pathogen also causes twig and leaf diseases in several common

nursery and landscape plants.

What To Look For

Symptoms vary on different types of plants. They can include:

Trunk and branch cankers

Brown to black lesions on leaves

Twig dieback

An official diagnosis must be made by a trained professional and confirmed by

laboratory testing. If you believe your plant may be infected with P. ramorum, please

take the following actions:

1. Check the list of plants that are susceptible to P. ramorum (319.67 KB) to see if

your plant type is there.

2. Compare the symptoms you're seeing to the California Oak Mortality Task Force

Symptom Gallery.

3. Report symptomatic plants to your State plant health director or State plant

regulatory official.

How To Prevent This Disease

P. ramorum can infect several native and non-native plant species, including many

common nursery and landscape plants. To prevent disease spread:

Only buy healthy plants from reputable sources.

Do not move plants that appear sick or dying.

Disinfest pruning and other gardening tools between plants.

Because P. ramorum is a water mold that thrives in wet conditions, reduce

standing water in your yard or garden and avoid overhead irrigation.
How It Is Treated

There is no treatment for P. ramorum infection. Prevention is the best defense.

Report Plant Pests and Diseases

Have you seen this pest or signs of pest damage? Immediately report your findings.

Find your State plant regulatory official

Find your State plant health director

Controlling Phytophthora ramorum

Current Status

APHIS works to limit the spread of P. ramorum from regulated nurseries and

quarantine areas to nurseries and areas that are free of the pathogen. We use both

regulatory and non-regulatory strategies to achieve this goal. This includes public

education, quarantines, inspections, surveys, and a compliance program.

Detection History

Sudden oak death was first reported in 1995 on a tanoak in Marin County, California.

Since then, the P. ramorum pathogen has been confirmed on various native hosts in

16 counties in California (Alameda, Contra Costa, Del Norte, Humboldt, Lake, Marin,

Mendocino, Monterey, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz,

Solano, Sonoma, and Trinity) and 1 county in Oregon (Curry). Through ongoing

surveys, APHIS continues to define the extent of the pathogen's distribution in the

United States.

Regulatory Information

Quarantined and Regulated Counties Map (2.69 MB) (April 2022)

Federal Regulations, 7 CFR 301.92 - 301.92-12

Federal Order: Restrictions on P. ramorum Host Plant Imports (4/18/2012)

Canadian Food Inspection Agency Current Import Requirements

Information for Cooperators
Phytophthora ramorum Domestic Regulatory Program Manual

List of Proven Hosts and Plants Associated with P. Ramorum

Diagnostic, Sampling, Response, and Survey Information

Critical Control Point Assessment Template (285.88 KB)

Diagnostics Work Instruction Table (231.89 KB)

Current versions of all Work Instructions are available on the APHIS

Laboratory Portal

Potentially Actionable Suspect Sample (PASS) System (Revised 3/2024)

Symptoms Associated With P. ramorum

Nursery Survey Questionnaire (489.71 KB)

PPQ Form 391 (364.31 KB)

2013 P. ramorum Farm Bill Nursery Survey Criteria (167.83 KB)

National Plant Diagnostics Network

Reports and Assessments

Pest Risk Assessment (2.44 MB) (January 2008)

National Quality Assurance Program Review Report (90.37 KB) (October 2009)

National Program Review (198.38 KB) (December 2009)

Nursery Best Management Practices

National Ornamental Research Site Best Management Practices Manual

Presidio Phytophthora Management Recommendations

Safe Procurement and Production Manual: A Systems Approach for the

Production of Healthy Nursery Stock

UC Davis Best Management Practices for Phytophthora ramorum

Contact Us

William Wesela

National Policy Manager
Email: william.d.wesela@usda.gov

Phone: 301-851-2229