Transcript Sudden Oak Death

Sudden Oak Death:
Is the Sky Falling?
(or why I should take INT 256)
Prepared by: Mike Maguire, April 2003
Updated by: W.H. Livingston, February 2005
Web Sites
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Pest Alert East:
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Pest AlertWest
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http://www.na.fs.fed.us/spfo/pubs/pest_al/sodwest/pdf/s
odwest.pdf
California Oak Mortality Task Force
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http://www.na.fs.fed.us/spfo/pubs/pest_al/sodeast/sodeast
.pdf
http://nature.berkeley.edu/comtf/html/about_p__ramorum
.html
“Minority Report”
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http://phytosphere.com/tanoakobservations/tanoak.html
Sudden Oak Death
(SOD)
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Recent epidemic (1995 present)
Northern California,
southern Oregon
Dying of oak in urban and
forested areas
Tanoak (Lithocarpus densiflorus)
 California Black Oak
(Quercus Kelloggi)
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Why Worry?
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Might cause widespread mortality
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Could spread quickly
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“New” fungal pathogen in multiple
locations – amount of natural
resistance uncertain
Large number of susceptible species,
especially nursery plants
Unknown vector(s) of disease
transmission
Difficult to identify
On nursery plants
>$28 million government funding
UC Berkeley
Tanoak
Management
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Natural
Regeneration
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Wildlife
Fuel wood
Pulp
Shade Trees
Black Oak
Tanoak Adaptations
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Range: Native to Oregon
and California
Climate: Hot dry summers and
cool moist winters
Soils: Prefer deep and well drained soils
Disturbance: Very susceptible to fire
Regeneration: Sprout prolifically after fire or harvest
Shade tolerant
Most common hardwood in CA & OR Coast Ranges
Best adapted to Humboldt & Mendocino Counties
(northern CA coast)
Other Susceptible
Species
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Total of 31 species
affected
Rhododendron
most important
Two types of hosts:
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Bark canker hosts:
e.g. California black
oak and tanoak
Foliar hosts: e.g.
tanoak
Symptoms: Bark
Canker
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Sunken cankers on mature
trees
Produce reddish-brown to
tar-black viscous seep
Seeping is the most reliable
symptom
Symptom: Oak Death
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Canker girdles stem
Sudden simultaneous leaf death on a major stem or entire
tree (“Sudden Oak <Leaf> Death”)
Symptom:
Leaf & Shoot
Blight
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Most common
symptom, especially on
Rhododendron
Impact on Oaks
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Oak mortality has reached
“unprecedented levels,” but
can’t find how much
Distribution is patchy but
40%-80% of a stand can be
impacted
Pathogen: Overview of Phytopthora
Species
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Adapted to areas with
high moisture
Reproduce both sexually
and asexually
Has spore stages that can
survive for extended
periods, even in adverse
conditions
Pathogen: Phytopthora ramorum
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Timeline:
Described in Europe – 1993
 Identified in California – 1999
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Difficult to Identify
Approximately 60 similar species
 No single symptom is adequate for
diagnosis
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Fungal Pathogen
Signs
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No visible signs
Two methods available
to identify P. ramorum
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Culture fungus from the
border of an active
infection
Amplify DNA using
polymerase chain reaction
(PCR)
Where Found, What’s at Risk
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Coast of northern
California
Potential to spread
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Further up west
cost
Moderate, moist
climates in east
USFS Photo
Life Cycle of Phytopthora ramorum
Life Cycle
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Zoospores infect host
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short lived and motile
asexual
swim several feet
Chlamydospores
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Go dormant
Can survive
environmental
extremes
If land on plant, can
germinate and infect
Environment Favoring Phytophthora
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Cool temperatures (50-65 F)
High moisture levels, water
films on leaf and bark
surfaces
Proximity of other hosts:
(e.g. California bay laurel,
Rhododendron, Madrone,)
Forest edges with broad
canopies: greater likelihood
of spores intercepting tree
crowns
Predisposing Factors Related to
Degree of Stress
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Fog
Precipitation &
temperature
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El Nino effects?
El Niño And La Niña Years: A Consensus List
1988-89
Strong La Niña
1989-90
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1990-91
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1991-92
El Niño
1992-93
El Niño
1993-94
El Niño
1994-95
Moderate El Niño
1995-96
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1996-97
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1997-98
Strong El Niño
1998-99
La Niña
1999-00
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2000-01
La Niña
2001-02
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Predisposing Factors Related to
Tree Species Adaptations to Fungus
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Largely unknown
P. ramorum is considered very
aggressive; can infect and kill
healthy trees.
However,
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Symptoms appeared simultaneously
over a large area
Most severe on tan oak outside of
preferred habitat
“Minority Report”
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http://phytosphere.com/tanoakobser
vations/tanoak.html
Pathogen Movement
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P. ramorum has been isolated in firewood, leaves, nursery
stock, soil, stream water, and rain splash.
Long distance spread may be due to human movement
of infested host materials
Local spread of disease may be due to infested soil and
rain splash
Insects and/or birds as vectors?
Tan oak abundance affected by land
use history
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Stems die easy; roots don’t die:
1000 yr old
Regenerated after widespread
cutting (after 1930?)
Now mature
Fire exclusion
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Increased density and high
competition
Tan oak stands have been
predisposed to diseases and
secondary pests
Predisposing Factors
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Presence of P. ramorum
Presence of vulnerable hosts: Maturing tanoak
on disturbed sites
Presence of alternate hosts (e.g. Rhododendron,
California bay laurel)
Rain/fog belt: geographic area within 50 miles
of coast
Excessive rainfall
Contributing Factors
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Beetles: Populations have exploded in recent years,
usually attacking severely stressed, dying or dead trees
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Fungus: Associated with dead oaks and tanoaks
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Western Oak Bark Beetle (Pseudopityophthorus pubipennis)***
Oak Ambrosia Beetle (Monarthrum scutellare)
Minor Oak Ambrosia Beetle (Monarthrum detinger)
Hypoxylon thourarsianum
Drought: Weakens infected trees further
Control Options: Preemptive
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Harvest Layout
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Sanitation
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Avoid in infected areas, especially
during wet periods.
Wash stations
Shoes, vehicles, machinery, etc.
Before and after entering
uninfected areas
Education and Communication
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Focus on locations of infected
areas and possible modes of
dispersal
Quarantines
Reactive Measures
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Prune infected branches
and destroy
Cut and Burn
Chemical Control
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Agri-fos
Phosphate based
Inject or spray
Shade trees only
No Action
Conclusions
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Sudden oak death
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The disease is complex
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Name is bad science – not descriptive
Great for publicity
Moisture is key predisposing
factor
Stressed trees probably
important predisposing factor
Pathogen will spread
Been in forest for years?
Efforts to prevent spread of pathogen should continue
Because of cold climate, doubt that pathogen will get
established in Northeast. Lacks fog belt, too.