Sudden Oak Death:Sudden Oak Death:Is the Sky Falling?Is the Sky Falling?

(or why I should take INT 256)(or why I should take INT 256)

Prepared by: Mike Maguire, April Prepared by: Mike Maguire, April 20032003

Updated by: W.H. Livingston, Updated by: W.H. Livingston, February 2005February 2005

Web SitesWeb Sites Pest Alert East:Pest Alert East:

http://www.na.fs.fed.us/spfo/pubs/pest_al/sodeast/sodeast.pdf

Pest AlertWestPest AlertWest http://www.na.fs.fed.us/spfo/pubs/pest_al/sodw

est/pdf/sodwest.pdf California Oak Mortality Task ForceCalifornia Oak Mortality Task Force

http://nature.berkeley.edu/comtf/html/about_p__ramorum.html

““Minority Report”Minority Report” http://phytosphere.com/tanoakobservations/http://phytosphere.com/tanoakobservations/

tanoak.htmltanoak.html

Sudden Oak Sudden Oak Death (SOD)Death (SOD)

Recent epidemic (1995 Recent epidemic (1995 - present)- present)

Northern California, Northern California, southern Oregonsouthern Oregon

Dying of oak in urban Dying of oak in urban and forested areasand forested areas Tanoak (Tanoak (Lithocarpus Lithocarpus

densiflorusdensiflorus)) California Black OakCalifornia Black Oak

( (Quercus Kelloggi)Quercus Kelloggi)

Why Worry?Why Worry? Might cause widespread Might cause widespread

mortalitymortality ““New” fungal pathogen in New” fungal pathogen in

multiple locations – amount of multiple locations – amount of natural resistance uncertainnatural resistance uncertain

Large number of susceptible Large number of susceptible species, especially nursery plantsspecies, especially nursery plants

Could spread quicklyCould spread quickly Unknown vector(s) of disease Unknown vector(s) of disease

transmissiontransmission Difficult to identifyDifficult to identify On nursery plantsOn nursery plants

>$28 million government >$28 million government fundingfunding

UC Berkeley

ManagemManagementent

Natural Natural RegenerationRegeneration WildlifeWildlife Fuel woodFuel wood PulpPulp

Shade TreesShade Trees

Black Black OakOakTanoakTanoak

Tanoak Tanoak AdaptationsAdaptations

Range: Native to Oregon Range: Native to Oregon and Californiaand California

Climate: Hot dry summers and Climate: Hot dry summers and cool moist winterscool moist winters

Soils: Prefer deep and well drained soilsSoils: Prefer deep and well drained soils Disturbance: Very susceptible to fireDisturbance: Very susceptible to fire Regeneration: Sprout prolifically after fire or Regeneration: Sprout prolifically after fire or

harvestharvest Shade tolerantShade tolerant Most common hardwood in CA & OR Coast Most common hardwood in CA & OR Coast

RangesRanges Best adapted to Humboldt & Mendocino Best adapted to Humboldt & Mendocino

Counties (northern CA coast)Counties (northern CA coast)

Other Other Susceptible Susceptible

SpeciesSpecies Total of 31 Total of 31

species affected species affected Rhododendron Rhododendron

most importantmost important Two types of Two types of

hosts:hosts: Bark canker Bark canker

hosts: e.g. hosts: e.g. California black California black oak and tanoakoak and tanoak

Foliar hosts: e.g. Foliar hosts: e.g. tanoaktanoak

Symptoms: Symptoms: Bark CankerBark Canker

Sunken cankers on Sunken cankers on mature treesmature trees

Produce reddish-Produce reddish-brown to tar-black brown to tar-black viscous seepviscous seep

Seeping is the most Seeping is the most reliable symptomreliable symptom

Symptom: Oak DeathSymptom: Oak Death Canker girdles stemCanker girdles stem Sudden simultaneous leaf death on a major stem Sudden simultaneous leaf death on a major stem

or entire tree (“Sudden Oak <Leaf> Death”)or entire tree (“Sudden Oak <Leaf> Death”)

Symptom: Symptom: Leaf & Leaf & Shoot Shoot BlightBlight Most common Most common

symptom, especially symptom, especially on Rhododendronon Rhododendron

Impact on Impact on OaksOaks

Oak mortality has Oak mortality has reached reached “unprecedented “unprecedented levels,” but can’t find levels,” but can’t find how muchhow much

Distribution is patchy Distribution is patchy but 40%-80% of a but 40%-80% of a stand can be stand can be impactedimpacted

Pathogen: Overview of Pathogen: Overview of PhytopthoraPhytopthora Species Species

Adapted to areas Adapted to areas with high moisturewith high moisture

Reproduce both Reproduce both sexually and sexually and asexuallyasexually

Has spore stages Has spore stages that can survive that can survive for extended for extended periods, even in periods, even in adverse conditionsadverse conditions

Pathogen:Pathogen: Phytopthora Phytopthora ramorumramorum

Timeline:Timeline: Described in Europe – 1993Described in Europe – 1993 Identified in California – 1999 Identified in California – 1999

Difficult to Identify Difficult to Identify Approximately 60 similar speciesApproximately 60 similar species No single symptom is adequate for No single symptom is adequate for

diagnosisdiagnosis

Fungal Fungal Pathogen Pathogen

SignsSigns No visible signsNo visible signs Two methods Two methods

available to available to identify identify P. P. ramorumramorum Culture fungus Culture fungus

from the border of from the border of an active infectionan active infection

Amplify DNA using Amplify DNA using polymerase chain polymerase chain reaction (PCR)reaction (PCR)

Where Found, What’s at Where Found, What’s at RiskRisk

Coast of Coast of northern northern CaliforniaCalifornia

Potential to Potential to spreadspread Further up west Further up west

costcost Moderate, Moderate,

moist climates moist climates in east in east

USFS Photo

Life Cycle of Life Cycle of Phytopthora ramorumPhytopthora ramorum

Life CycleLife Cycle

Zoospores infect Zoospores infect hosthost short lived and short lived and

motile motile asexualasexual swim several feetswim several feet

Chlamydospores Chlamydospores Go dormantGo dormant Can survive Can survive

environmental environmental extremesextremes

If land on plant, If land on plant, can germinate and can germinate and infectinfect

Environment Favoring Environment Favoring PhytophthoraPhytophthora

Cool temperatures (50-Cool temperatures (50-65 F) 65 F)

High moisture levels, High moisture levels, water films on leaf and water films on leaf and bark surfacesbark surfaces

Proximity of other hosts: Proximity of other hosts: (e.g. California bay (e.g. California bay laurel, Rhododendron, laurel, Rhododendron, Madrone,)Madrone,)

Forest edges with broad Forest edges with broad canopies: greater canopies: greater likelihood of spores likelihood of spores intercepting tree intercepting tree crownscrowns

Predisposing Factors Related Predisposing Factors Related toto

Degree of Stress Degree of Stress FogFog Precipitation & Precipitation &

temperaturetemperature El Nino effects?El Nino effects?

1988-89 Strong La Niña

1989-90 -

1990-91 -

1991-92 El Niño

1992-93 El Niño

1993-94 El Niño

1994-95 Moderate El Niño

1995-96 -

1996-97 -

1997-98 Strong El Niño

1998-99 La Niña

1999-00 -

2000-01 La Niña

2001-02 -

El Niño And La Niña Years: A Consensus List

Predisposing Factors Related Predisposing Factors Related toto

Tree Species Adaptations to Tree Species Adaptations to FungusFungus Largely unknownLargely unknown

P. ramorumP. ramorum is considered is considered very aggressive; can infect very aggressive; can infect and kill healthy trees.and kill healthy trees.

However, However, Symptoms appeared Symptoms appeared

simultaneously over a large simultaneously over a large areaarea

Most severe on tan oak Most severe on tan oak outside of preferred habitatoutside of preferred habitat

““Minority Report”Minority Report” http://phytosphere.com/http://phytosphere.com/

tanoakobservations/tanoakobservations/tanoak.htmltanoak.html

Pathogen MovementPathogen Movement P. ramorumP. ramorum has been isolated in firewood, has been isolated in firewood,

leaves, nursery stock, soil, stream water, leaves, nursery stock, soil, stream water, and rain splash.and rain splash.

Long distance spread may be due to Long distance spread may be due to human movement of infested host human movement of infested host materialsmaterials

Local spread of disease may be due to Local spread of disease may be due to infested soil and rain splashinfested soil and rain splash

Insects and/or birds as vectors?Insects and/or birds as vectors?

Tan oak abundance affected Tan oak abundance affected by land use historyby land use history

Stems die easy; roots Stems die easy; roots don’t die: 1000 yr olddon’t die: 1000 yr old

Regenerated after Regenerated after widespread cutting (after widespread cutting (after 1930?)1930?)

Now matureNow mature Fire exclusionFire exclusion

Increased density and high Increased density and high competitioncompetition

Tan oak stands have been Tan oak stands have been predisposed to diseases predisposed to diseases and secondary pestsand secondary pests

Predisposing FactorsPredisposing Factors

Presence of Presence of P. ramorumP. ramorum Presence of vulnerable hosts: Presence of vulnerable hosts:

Maturing tanoak on disturbed sitesMaturing tanoak on disturbed sites Presence of alternate hosts (e.g. Presence of alternate hosts (e.g.

Rhododendron, California bay laurel)Rhododendron, California bay laurel) Rain/fog belt: geographic area Rain/fog belt: geographic area

within 50 miles of coastwithin 50 miles of coast Excessive rainfallExcessive rainfall

Contributing FactorsContributing Factors

Beetles: Populations have exploded in recent Beetles: Populations have exploded in recent years, usually attacking severely stressed, years, usually attacking severely stressed, dying or dead treesdying or dead trees Western Oak Bark Beetle (Western Oak Bark Beetle (Pseudopityophthorus Pseudopityophthorus

pubipennispubipennis)***)*** Oak Ambrosia Beetle (Oak Ambrosia Beetle (Monarthrum scutellareMonarthrum scutellare)) Minor Oak Ambrosia Beetle (Minor Oak Ambrosia Beetle (Monarthrum detingerMonarthrum detinger))

Fungus: Associated with dead oaks and tanoaksFungus: Associated with dead oaks and tanoaks Hypoxylon thourarsianumHypoxylon thourarsianum

Drought: Weakens infected trees furtherDrought: Weakens infected trees further

Control Options: Control Options: PreemptivePreemptive

Harvest LayoutHarvest Layout Avoid in infected areas, Avoid in infected areas,

especially during wet periods.especially during wet periods. SanitationSanitation

Wash stationsWash stations Shoes, vehicles, machinery, Shoes, vehicles, machinery,

etc. etc. Before and after entering Before and after entering

uninfected areasuninfected areas Education and Education and

CommunicationCommunication Focus on locations of infected Focus on locations of infected

areas and possible modes of areas and possible modes of dispersaldispersal

QuarantinesQuarantines

Reactive Reactive MeasuresMeasures

Prune infected Prune infected branchesbranches and destroy and destroy

Cut and BurnCut and Burn Chemical ControlChemical Control

Agri-fosAgri-fos Phosphate basedPhosphate based Inject or sprayInject or spray Shade trees onlyShade trees only

No ActionNo Action

ConclusionsConclusions Sudden oak deathSudden oak death

Name is bad science – not descriptiveName is bad science – not descriptive Great for publicityGreat for publicity

The disease is complexThe disease is complex Moisture is key predisposing Moisture is key predisposing

factorfactor Stressed trees probably Stressed trees probably

important predisposing factorimportant predisposing factor Pathogen will spreadPathogen will spread Been in forest for years?Been in forest for years?

Efforts to prevent spread of pathogen should Efforts to prevent spread of pathogen should continuecontinue

Because of cold climate, doubt that pathogen Because of cold climate, doubt that pathogen will get established in Northeast. Lacks fog will get established in Northeast. Lacks fog belt, too.belt, too.