Phytophthora ramorum
A short course
Presented by the
California Oak Mortality Task Force
Part 3 - Regulations and
Management of
Phytophthora ramorum
Background Photo Credits:
Karl Buermeyer, UC Cooperative Extension (forest scenes, lone oak)
Stephen Eales, Plant Health and Seed Inspectorate, DEFRA, UK (mountain laurel)
Jan Hedberg, Oregon Department of Agriculture (viburnums in nursery)
Steve Tjosvold, UC Cooperative Extension (rhododendron)
Course Outline
Part 1 - Introduction to Phytophthora
ramorum and Sudden Oak Death
Part 2 - Symptom Recognition,
Diagnosis, and Sampling
Part 3 - Regulations and Management of
Phytophthora ramorum
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Regulations and Quarantines
Minimizing Spread in Wildlands and Landscapes
Preventing Disease Transfer between Nurseries
Preventing Infection from Surrounding
Woodlands
Preventing Favorable Disease Conditions in the
Nursery
Preventative Chemical Treatments
Review Questions
Part 3
Regulations and Management
of Phytophthora ramorum
Regulations and quarantines have been
established to minimize the artificial
spread of Phytophthora ramorum. Best
Management Practices (BMPs) have been
developed to aid in disease prevention.
Regulations and Quarantines
In California, County Agricultural Commissioners and the
California Department of Food and Agriculture are responsible for
enforcing quarantines, and for dealing with nursery detections as
well as wildland infestations. The California Department of
Forestry and Fire Protection enforces regulations to prevent
disease spread during timber operations on private land in
infested areas. The USDA Animal and Plant Health Inspection
Service (APHIS) regulates interstate commerce, and works with
other countries to develop international shipping agreements.
As of April 2004, countries with regulations on the importation of
Phytophthora ramorum host material include: Canada, the UK,
South Korea, New Zealand, Australia, the Czech Republic,
Mexico, Taiwan, the US, the European Union, and others.
Since regulations and quarantines vary from region to
region and are subject to change, it is best to refer to
the following resources for up-to-date regulatory
information:
• California Department of Food and Agriculture:
www.cdfa.ca.gov/phpps/pe/sod_survey/
• California County Agricultural Commissioners:
www.cdfa.ca.gov/exec/cl/countyagmap.htm
• Oregon Department of Agriculture:
www.oda.state.or.us/plant/ppd/path/SOD/
• Washington State Department of Agriculture: agr.wa.gov
• USDA APHIS: www.aphis.usda.gov/ppq/ispm/sod/
• Canadian Food Inspection Agency:
www.inspection.gc.ca/english/plaveg/protect/dir/d-01- 01e.shtml
• Department for Environment, Food and Rural Affairs (UK):
www.defra.gov.uk/planth/pramorum.htm
Users in states other than California, Washington, and Oregon
should contact their state or county agriculture departments.
Minimizing Spread in Wildlands and Landscapes
As described in Part 1 of this course, under “Biology,”
Phytophthora ramorum survives and spreads best under
moist, cool conditions. Wet conditions can cause soil and
plant material to adhere to vehicles, equipment, and
footwear. Whenever possible, it is always best to avoid
visiting an infested area, especially during the rainy season.
Always know when you are working or recreating in a
Phytophthora ramorum-infested area so that proper
sanitary measures can be practiced and to assure
compliance with state and federal regulations. When
in an infested area, especially where conditions are
wet, keep vehicles on paved or gravel surfaces if
possible. Before leaving the infested area, check
yourself, pet(s), vehicle, and equipment to ensure
that all mud, soil, organic material, and plant debris
(leaves, twigs, etc.) are removed. Lysol, 70%
alcohol, or a 10% bleach solution can be used to kill
any remaining spores. Keep a cleaning kit (bucket,
scrub brush, cleaning solution, & towels) in your
vehicle, and use separate tools and footwear in
infested areas if possible.
Dead and dying bark hosts rarely
infect other trees. If dead or dying
diseased trees are felled for hazard
reduction, it is best to leave all
material on-site when possible. An
excellent way to dispose of larger
woody material is to use it as
firewood on-site. Smaller material can
be chipped and used as mulch on-site,
or lopped and scattered close to the
ground to reduce fire hazard. While
commercial composting of infested
material is effective at killing the
pathogen, homeowner composting is
not recommended.
Janice Alexander, UC Cooperative Extension
If infested material must be removed from the site, it should be
carefully covered and taken to an approved disposal site within the
regulated area, such as an approved landfill, composting facility, or
designated collection site for diseased material.
Preventing Disease Transfer between
Nurseries
To minimize the risk of infested plant material
being transported between nurseries, the
following BMPs* should be implemented:
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Confirm that host stock is propagated from onsite materials, or is received from shipping
nurseries under compliance agreements.
* Nursery BMPs developed by the COMTF Nursery SubcommitteeKaren Suslow, Hines Horticulture, and Gail Raabe, San Mateo Co.
Agricultural Commissioner, Co-Chairs
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Have trained personnel inspect all incoming
host plants, regardless of origin, for
Phytophthora ramorum symptoms prior to
incorporating them into the production facility.
Segregate these plants from other host plants,
and periodically inspect them for symptoms
over the course of a growing season.
Off-load incoming shipments to an area that
can be cleaned of leafy debris. Sweep debris
from the loading pad and truck, and bag it for
disposal.
Maintain accurate shipping documentation
including product, amount, date, and origin to
facilitate trace-backs and trace-forwards.
Preventing Infection from Surrounding Woodlands
If a nursery is located in an area where Phytophthora
ramorum is found naturally, there are steps that
should be taken to minimize the chance of nursery
plants becoming infected.
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Monitor host plants in the surrounding area for
disease symptoms, especially in the spring and
summer.
If practical, remove host plants within 100 feet
of the nursery perimeter.
Install diversion berms to prevent soil and water
movement from surrounding hillsides during
storm events.
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Place containers/pots on a soil barrier such as
gravel, or on raised beds.
Monitor irrigation water from sources other
than well or municipal water sources to
ensure that it is pathogen-free.
Overhead irrigation greatly increases the
chances of introduction and spread of
Phytophthora ramorum, especially in generally
infested areas. Use drip irrigation wherever
possible. If overhead watering must be used,
irrigate in the morning to allow for drying by
nightfall.
Preventing Favorable Disease Conditions
in the Nursery
Should inoculum or infected plants enter the nursery,
it is important to avoid conditions that may foster
the pathogen’s survival and spread. The following
precautions are recommended to help safeguard
nurseries from internal infestations.
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Shading and overhead irrigation create cool,
humid conditions that, while favorable for some
nursery crops, are also favorable for the spread
and survival of Phytophthora ramorum. Avoid
these conditions where possible.
Correct low spots or poor drainage that may
accumulate water for extended periods. Check
and maintain irrigation systems to avoid leaks
and uneven watering.
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Wounded leaves are the most susceptible to
infection. Wherever possible, avoid moving or
handling plants during times when environmental conditions favor the pathogen.
Locate soil and cull piles as far as possible from
plants, and cover with clear polyethylene
sheets. Dispose of culled plants and plant
material as soon as possible.
Make sure that all nursery workers are aware of
the potential for Phytophthora ramorum
infestations, and are familiar with symptoms
for early detection.
Preventative Chemical Treatments
While there is no known cure for
Phytophthora ramorum, there is
currently a preventative phosphite
fungicide treatment available for use in
high-risk landscape settings. In
California, risk is largely based on
proximity to California bay laurels.
As the treatment is relatively expensive
and time consuming, it is not practical
for wildland situations.
Doug Schmidt, UC Berkeley
When treating a tree, the material is injected into the cambium,
or sprayed directly on to the lower trunk of bark hosts. Two
treatments 6 months apart are required the first year, with yearly
treatments thereafter.
There is currently no eradicative
treatment for Phytophthora
ramorum on foliar hosts.
Research is ongoing to find
treatments to prevent foliar
hosts, particularly ornamentals,
from becoming infected and
spreading the disease.
Karl Buermeyer,
UC Cooperative Extension
Review Questions
1. What are the two broad categories of measures
taken to minimize the spread of Phytophthora
ramorum?
1. Regulations and Quarantines
2. Best Management Practices
2. Name 3 levels of commerce that require regulating,
and are under different jurisdictions.
1. Within a state (Intrastate)
2. Between states (Interstate)
3. International
3. At what time of year, or under what conditions, are
extra precautions necessary when working in
Phytophthora ramorum-infested areas?
Under moist conditions or during wet times of the
year
Review Questions, continued
4. What should always be done before leaving
an infested area?
Remove host plant material and soil from footwear,
vehicles, and equipment
5. What is the best way to dispose of infested plant
material?
Burn as firewood on the property, or leave it on site
6. List 4 BMPs to prevent Phytophthora ramorum spread
between nurseries.
1.
2.
3.
4.
Confirm stock source is not infested
Inspect incoming host material for symptoms
Clean and dispose of debris from shipping area
Keep records of all shipping transactions
Review Questions, continued
7. Name 3 sources of infection for nursery plants in
Phytophthora ramorum-infested areas.
1. Infected host plants around the perimeter
2. Soil and water runoff from hillsides
3. Irrigation water from infested water sources
8. What conditions in a nursery may make its
environment more susceptible to Phytophthora ramorum
infestations?
Shading with overhead irrigation
9. What should be true about a host tree before
considering it for preventative phosphite treatment?
It should be a high-value tree, at risk of becoming
infected
For additional information on
Phytophthora ramorum and Sudden
Oak Death, please visit the California
Oak Mortality Task Force website:
www.suddenoakdeath.org