Phytophthora ramorum

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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)
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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
• 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

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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.
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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.
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• 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/protec
  t/dir/d-01- 01e.shtml
• Department for Environment, Food and Rural
  Affairs (UK) www.defra.gov.uk/planth/pramorum.ht
  m
• Users in states other than California,
  Washington, and Oregon should contact their state
  or county agriculture departments.

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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.
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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.
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.
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Preventing Disease Transfer between Nurseries
To minimize the risk of infested plant material
being transported between nurseries, the
following BMPs should be implemented

• Confirm that host stock is propagated from
  on-site materials, or is received from shipping
  nurseries under compliance agreements.

Nursery BMPs developed by the COMTF Nursery
Subcommittee- Karen 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.

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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.

• 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.

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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 pathogens survival and spread.
The following precautions are recommended to help
safeguard nurseries from internal infestations.

• 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 environ-mental
  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.

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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.
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.

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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.

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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
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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. Confirm stock source is not infested 2.
Inspect incoming host material for symptoms 3.
Clean and dispose of debris from shipping area 4.
Keep records of all shipping transactions
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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
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For additional information on Phytophthora
ramorum and Sudden Oak Death, please visit the
California Oak Mortality Task Force
website www.suddenoakdeath.org