Sudden Oak Death: biology and managementPathogen Hosts Environment Interactions Man.

Sudden Oak Death: biology and management

PathogenPathogen

HostsHosts

EnvironmentEnvironment InteractionsInteractions

Man

Phytophthora ramorum: Sudden Oak Death

Phytophthora kernoviae: blights & cankers, UK

Phytophthora alni: Alder decline, Europe

Phytophthora pinifolia: Daño Foliar del Pino, Chile(Pine needle blight)

Phytophthora quercina: Oak decline, Europe

Historic:

Phytophthora cinnamomi: Jarrah decline, Australia

Phytophthora lateralis: Pt. Orf. Cedar Root Disease, OR/CA

Phytophthora forest diseases:

Phytophthora diseases:

Well known in ag systems on numerous crops

Destructive in poorly drained soils or cool wet climates.

Disperse via motile zoospores

Survive as thick-walled chlamydospores or oospores

Mainly root diseases

Some cause aerial diseases of foliage, shoots or trunks

Sudden Oak Death

Mortality since 1990s

Phytophthora ramorum sp. nov. identified 2001

Consistent expansion of range (depends on season)

Wide host range reminiscent of P. cinnamomi

Sudden Oak Death

Lethal trunk infections on some native Quercus spp. & Tanoak

California Bay Laurel principal cause of dissemination in forests

Hosts like Rhododendron, Camellia, & Viburnum significant for spread through ornamental stock

Sudden Oak Death

Spread aerially by wind & rain during mildwet season

Introduced into new areas on infested ornamental stock

May be moved by people in infested soil or plant debris.

Starting in 1994 in Santa Cruz County(but probably arrived late 1980s)

Phytophthora ramorum

Sporangia

Chlamydospores

SOD pathogen called SOD pathogen called Phytophthora ramorum Phytophthora ramorum arrivedarrivedto California in 80s on infected ornamental plantsto California in 80s on infected ornamental plants

Positive isolationP. ramorum

Known distribution of Phytophthora ramorum in August 2000

Known distribution of Phytophthora ramorum in August 2008

Positive isolationP. ramorum

(OAKMAPPER.ORG)

P. ramorumP. ramorum introduced at least 8 times in CA introduced at least 8 times in CA (Mascheretti et al. 2009). Multiple introductions and not (Mascheretti et al. 2009). Multiple introductions and not

ability to move far explain distribution of diseaseability to move far explain distribution of disease

Because pathogen is exotic, native flora has limited resistance to its attack and regular tree health maintenance simply will not suffice

Cluster 1 of strains is the

original introduced,

butothers are

more widespread

Distribution of SOD in California wildlands

• Distribution is result of discrete introductions followed by natural spread but only in favorable habitats (redwood-tanoak and mixed evergreen)

• As a result, distribution is extremely patchy in 14 contiguous coastal counties from Northern Humboldt to Southern Monterey

• Presence is extremely marginal in San Francisco, Solano, and Lake counties

Bay/Oak association

Bleeding cankerBleeding canker

Canker margin in phloemCanker margin in phloem

Bay Coast Live Oak (no sporulation)

SporangiaSoil

Yearly

Wave years

OaksCoast live oak

Quercus agrifolia

Black oakQ. kellogii

Shreve’s oakQ. parvula var. shrevei

Canyon Live oakQ. chrysolepis

TanoakNotholithocarpus densiflorus

Tanoak leaves alsovery infectious:-tanoaks behave bothas oaks and bay

Hypoxylon Hypoxylon (Anulohypoxylon) (Anulohypoxylon) fruitbodies on the main fruitbodies on the main stem are a sign that a tree stem are a sign that a tree is functionally deadis functionally dead

Only health compromised trees attract bark and Only health compromised trees attract bark and ambrosia beetles: frass (sawdust) on the trunk is ambrosia beetles: frass (sawdust) on the trunk is

a sign of insect colonizationa sign of insect colonization

Tanoak vs. Oak mortality

• Tanoak – Big Sur– 70%

• Marin – predicted– 15 years for 90%

• Oak- Big Sur– 40%

• Marin – predicted– 35 years for 90%

Confirmed Susceptible Species

Andrew's clintonia bead lilyArdisiaBearberryBigleaf mapleBlueblossomCalifornia bay laurelCalifornia black oakCalifornia buckeye California coffeeberry California hazelnut California honeysuckleCalifornia maidenhair fernCalifornia nutmegCalifornia wood fernCamellia speciesCamphor treeCanyon live oakCascaraChinese witchhazel Chinese guger treeCoast live oakCoast redwoodDogwood speciesDouglas firEastern Joy Lotus TreeEuropean ashEuropean beech

European turkey oak European yewEvergreen huckleberryEvergreen mapleFalse Solomon’s sealFormosa firethornFetterbushGoat willowGrand firGriseliniaHollyHolly oliveHolm oakHorse chestnutHybrid witchhazelJapanese evergreen oakLaurustinusLeucothoe speciesLilacLoropetalum speciesMadroneMagnolia varitiesManzanitaMicheliaMountain laurel

Myrtle-leafed DistyliumNorthern red oakOleanderOregon ashOregon grapeOsmanthusPacific yewPersian ironwoodPieris varietiesPlanetree maplePoison oakPrunus speciesRed firRed lotus treeRed tip photiniaRedwood ivyRhododendron speciesRoble beech Rosa species & hybridsRosa species & hybridsRugosa roseSalalSalmonberryScotch heatherScribbly gumSessile oak

Sheep laurelShreve’s oakSouthern red oakSpicebushSpike witch hazelSpreading euonymusStar magnolia Strawberry treeStriped bark mapleSweet bay laurelSweet chestnutSweet CicelySweet oliveTanoakToyonViburnum varietiesVictorian boxVine mapleWestern maidenhair

fern Western starflowerWhite firWinter's barkWitch hazelWood roseYew

Primary cause of death is girdling of phloem, vessel blocking, while secondary organisms accelerate the

process

Girdling occurs much faster than visible symptoms on crown. Girdled trees can survive apparently “green” 4 years + after being girdled

Girdled trees can fail even if “green” because of activity of secondary organisms

While insecticides may temporarily prolong the life of treated trees, beetle attacks are a good indicator of “hazard” trees

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By inoculating with By inoculating with zoospores and without zoospores and without wounding, the ideal wounding, the ideal conditions for infection conditions for infection were figured out: these were figured out: these conditions are present in conditions are present in California especially when California especially when there are rainy late there are rainy late Springs: these conditions Springs: these conditions do not happen every year do not happen every year

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SOD spore catches in water: mid-April to mid-June is consistent

Synchrony pathogen-host:Host susceptibility

Susceptibility of oaksSusceptibility of oaks(lesion size in lab)(lesion size in lab)

Susceptibility of bay Susceptibility of bay laurelslaurels(lesion size in nature)(lesion size in nature)

PathogenPathogen

When multiple rain events occur sporangia are When multiple rain events occur sporangia are produced on leaves of infectious hosts such as produced on leaves of infectious hosts such as bay laurel and tanoak and can be airborne bay laurel and tanoak and can be airborne

mostly up to 100 m but when mostly up to 100 m but when winds are strong up to 2 mileswinds are strong up to 2 miles

New infections occur almost exclusively during the rainy season in or near sites previously infested

Limit tree-care and forestry work during wet season

If necessary to work in wet season, schedule to work in uninfested sites before working in infested sites

P. ramorum has a short spread range, knowing its fine scale distribution is essential

Sudden Oak Death: biology and managementPathogen Hosts Environment Interactions Man.

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