Sudden Oak Death in Washington State

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Sudden Oak Death in Washington State
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What is Sudden Oak Death?

• First seen in early 1990s
• Two types of symptoms
• Canker
• Foliar blight
• Caused by Phytophthora ramorum (Oomycetes)
• Over 70 plant hosts
• Most of the outbreak in central coastal CA

Dead tanoak in Muir Woods NP, CA
Foliar symptoms on Rhododendron
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Two distinct diseases caused by Phytophthora
ramorum

• Sudden Oak Death
• Red oaks, beech, and tanoak
• Stem lesions beneath the bark girdle and kill
  tree
• Cankers often bleed or ooze
• Can kill adult trees
• Dead end hosts
• P. ramorum foliar blight/Ramorum blight
• Non-oak hosts
• Spots and blotches on leaves shoot die back
• Can kill juvenile plants, usually not lethal for
  mature plants
• Spreads the disease

Slide from the USDA PRED Training Module
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Phytophthora spore stages

• Phytophthora thrives in wet conditions
• P. ramorum infections initiated by sporangia and
  zoospores
• Chlamydospores can persist in soil and leaf
  litter
• Sexual oospores are resistant to damage

Sporangia containing swimming zoospores
Chlamydospores
Oospores (P. infestans)
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How P. ramorum spreads

• Water - Wind-driven rain, irrigation, runoff
• Humans soil on hikers boots and bicycle tires,
  nursery plants
• Wildlife

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P. ramorum genetics

• Two mating types A1 and A2
• Three clonal lineages NA1, NA2, EU1

NA1 and NA2 All A2
EU1 Mostly A1, with a few A2
There is concern about NA and EU populations
mating, but this has not been observed
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P. ramorum in North American forests

• SOD currently found in 14 CA counties and 1 OR
  county
• These counties are under quarantine
• SOD not known to be established anywhere else in
  N.A. forests

Map from www.suddenoakdeath.org Kelly, UC-Berkeley
Slide from the USDA PRED Training Module
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Sudden Oak Death in California

• Tanoak (Lithocarpus densiflorus) and oak species
  affected
• Tree death primarily along urban-wildland
  interface
• Dying trees created hazards for residents
• Increased fire hazard in wildland areas from dead
  trees

Photo Marin County Fire Department
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• Infested area quarantined and eradication
  attempted
• 2001-2004 infested area decreased or remained
  the same
• 2005-present infested area increasing
• Area under quarantine now 166 sq miles

SOD in Oregon
Photo Everett Hansen, Oregon State University
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Risk of sudden oak death based on P. ramorum
climate matching and hardwood forest density in
the USA  
(High)
Fowler, G., Magarey, R., Colunga, M. 2006.
Climate-host mapping of Phytophthora ramorum,
causal agent of sudden oak death In Frankel,
Susan J. Shea, Patrick J. and Haverty, Michael
I., tech. coords. Proceedings of the sudden oak
death second science symposium the state of our
knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany,
CA Pacific Southwest Research Station, Forest
Service, U.S. Department of Agriculture 329-332
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P. ramorum in European forests
Rhododendron ponticum
Red Oak Quercus rubra
These species used as ornamentals in WA
Beech Fagus sylvatica
Photo DEFRA
Slide from the USDA PRED Training Module
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SOD Risk
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Washington P. ramorum surveys

• Nursery
• 2002 0
• 2003 1
• 2004 25
• 2005 16
• 2006 12
• 2007 7
• 2008 4

• Forest and stream
• 2002 ---
• 2003 ---
• 2004 ---
• 2005 0
• 2006 2
• 2007 6
• 2008 6

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What happens when P. ramorum is detected in a
nursery
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Summary of P. ramorum in Washington

• Found in nursery stock, not thought to be
  established
• in natural or urban landscape
• APHIS and WSDA conduct annual
• surveys to inspect production nurseries
• DNR conducts stream baiting and forest surveys
• Many plants native to Washington are
• known hosts
• Potential for impact on native ecosystem
• Quarantines may be imposed if detected in
  landscape

Slide by Norm Dart
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Recognizing Symptoms

• Sudden Oak Death of oaks
• Ramorum blight of other hosts
• Key to determine if samples should be submitted
  for P. ramorum testing in Washington
• focus on recently purchased (or near recently
  purchased) camellia, kalmia, lilac, pieris,
  rhododendron, or viburnum

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Symptoms on trees
P. cambivora on Beech

• Bleeding cankers
• Cankers can girdle the tree and kill it
• Host species in Fagaceae oaks, beech, tanoak
• Other Phytophthora spp can cause the same symptoms

P. ramorum on Oak
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Similar symptoms

• Phytophthora root disease and canker
• Armillaria root disease

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Bacterial stem diseases

• Bacterial wetwood
• Bleeding stem cankers caused by Pseudomonas
  syringae

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Important hosts of P. ramorum in WA nurseries

• Rhododendron
• Camellia
• Viburnum
• These genera account for over 90 of the positive
  finds in Washington nurseries
• Others
• Pieris
• Kalmia

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Rhododendron
Shoot blight
Leaf blotch on pacific rhododendron caused by
Phytophthora ramorum. Photo by Oregon Department
of Forestry.
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P. ramorum symptoms on native rhododendron
Shoot dieback
Foliar blight
Foliar blight
Rhododendron macrophyllum
Photo Everett Hansen, Oregon State University
Slide from the USDA PRED Training Module
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Root rot of rhododendron
Phytophthora root rot - not caused by P. ramorum
Slide from the USDA PRED Training Module
Photo Jay Pscheidt, Oregon State University
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Leaf necrosis of Rhododendron
Sun scorch, lesion does not extend down leaf
midrib
Gray blight can develop on sun scorched
Rhododendron leaves
Photo Rich Regan, Oregon State University
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P. ramorum on Camellia
Brown lesions irregular and restricted to leaf
tip
Photos Oregon Dept. of Agriculture Cheryl
Blomquist, CDFA
Slide from the USDA PRED Training Module
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Symptoms on camellia

• Look for lower leaves that have fallen off

Photo Cheryl Blomquist, CDFA
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Sun Scorch of Camellia
Brown spot not extending along petiole or midrib
of leaf
Slide by Norm Dart
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Viburnum
V. plicatum Mariesii
Viburnum tinus Spring Bouquet
V. davidii
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Symptoms
Grey mold

• Stem canker
• Foliage and shoot blight

Botrytis
P. ramorum
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Some other hosts
Grand fir
Bigleaf maple
Pacific madrone
Lilac
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Should an infected plant be submitted for
laboratory analysis?

• Plants likely to be infected by Phytophthora
  ramorum - Rhododendron, Camellia, and Viburnum
• Affected plant is on host list and purchased
  since 2002,
• Affected plant is near a recently purchased host
  plant
• Symptoms are consistent with Phytophthora
  ramorum
• Brown leaf spots with diffuse margins
• Shoot tip dieback

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Sample referral and submission

• In Washington state Master Gardeners and
  Extension Agents are asked to submit suspect
  samples to the WSU Puyallup Plant Clinic
• If you determine a sample should be submitted
• Download and fill out plant clinic sample form
  and follow approved procedures http//www.puyallup
  .wsu.edu/plantclinic/samples.htss.html
• Please consult the plant clinic before sending
  samples

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For more information please visit the WSU P.
ramorum education webpage http//www.puyallup.ws
u.edu/ppo/sod.html You may also call the WSU
Plant Diagnostic Lab at [phone] with
additional questions relating to P. ramorum
diagnostics or if you would like to have a plant
tested.
Slide by Norm Dart