Sudden Oak Death - State of Oregon : Oregon.gov Home … · • Sudden Oak Death is the common name...
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A guide for forest managers, Christmas tree growers, and forest-tree nursery operators in Oregon and Washington Sudden Oak Death: a summary • Sudden Oak Death is the common name for a disease caused by Phytophthora ramorum, a previously unknown and recently introduced non-native pathogen. • Phytophthora ramorum has killed hundreds of thousands of oak and tanoak trees in 14 coastal counties in California and hundreds of tanoak trees in Curry County, Oregon. • The pathogen has a wide host range including Douglas-fir, grand fir, coast redwood, and many other tree and shrub species common in Oregon and Washington forests. Tree mor- tality, branch and shoot dieback, and leaf spots result from infection depending on host species and location. • Phytophthora ramorum spreads aerially by wind and wind- driven rain and moves within forest canopies from tree tops to stems and shrubs and from understory plants to overstory trees. The pathogen survives in infested plant material, litter, soil, and water. It is moved long distances in nursery stock. • State and federal personnel regularly survey forests and nurs- eries in the Pacific Northwest to detect the disease. • Quarantine regulations, which include inspection and sanita- tion, are in place and are revised as necessary. • In Oregon and Washington, when infected plants are discov- ered, they and neighboring host plants are destroyed. • YOUR HELP is needed to protect Oregon and Washington from further damage from Phytophthora ramorum! E.M. Goheen, E. Hansen, A. Kanaskie, N. Osterbauer, J. Parke, J. Pscheidt, and G. Chastagner Ellen Michaels Goheen, USDA Forest Service, Pacific Northwest Region, Forest Health Pro- tection, Central Point, OR; Everett Hansen, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR; Alan Kanaskie, Oregon Department of Forestry, Salem, OR; Nancy Osterbauer, Oregon Department of Agriculture, Salem, OR; Jennifer Parke, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR; Jay Pscheidt, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR; and Gary Chastagner, Washington State University, Western Washington Research and Extension Center, Puyallup, WA. and Figure 1. A tanoak killed by Sudden Oak Death in Curry County, OR. Phytophthora ramorum Sudden Oak Death EM 8877 • April 2006 • $2.50
Transcript of Sudden Oak Death - State of Oregon : Oregon.gov Home … · • Sudden Oak Death is the common name...
A guide for forest managers, Christmas tree growers,
and forest-tree nursery operators in Oregon and Washington
Sudden Oak Death: a summary • SuddenOakDeathisthecommonnameforadiseasecaused
byPhytophthora ramorum,apreviouslyunknownandrecentlyintroducednon-nativepathogen.
• Phytophthora ramorumhaskilledhundredsofthousandsofoakandtanoaktreesin14coastalcountiesinCaliforniaandhundredsoftanoaktreesinCurryCounty,Oregon.
• ThepathogenhasawidehostrangeincludingDouglas-fir,grandfir,coastredwood,andmanyothertreeandshrubspeciescommoninOregonandWashingtonforests.Treemor-tality,branchandshootdieback,andleafspotsresultfrominfectiondependingonhostspeciesandlocation.
• Phytophthora ramorumspreadsaeriallybywindandwind-drivenrainandmoveswithinforestcanopiesfromtreetopstostemsandshrubsandfromunderstoryplantstooverstorytrees.Thepathogensurvivesininfestedplantmaterial,litter,soil,andwater.Itismovedlongdistancesinnurserystock.
• Stateandfederalpersonnelregularlysurveyforestsandnurs-eriesinthePacificNorthwesttodetectthedisease.
• Quarantineregulations,whichincludeinspectionandsanita-tion,areinplaceandarerevisedasnecessary.
• InOregonandWashington,wheninfectedplantsarediscov-ered,theyandneighboringhostplantsaredestroyed.
• YOURHELPisneededtoprotectOregonandWashingtonfromfurtherdamagefromPhytophthora ramorum!
E.M. Goheen, E. Hansen, A. Kanaskie, N. Osterbauer,
J. Parke, J. Pscheidt, and G. Chastagner
Ellen Michaels Goheen, USDA Forest Service, Pacific Northwest Region, Forest Health Pro-
tection, Central Point, OR; Everett Hansen, Department of Botany and Plant Pathology,
Oregon State University, Corvallis, OR; Alan Kanaskie, Oregon Department of
Forestry, Salem, OR; Nancy Osterbauer, Oregon Department of Agriculture, Salem, OR; Jennifer Parke, Department of Botany
and Plant Pathology, Oregon State University, Corvallis, OR; Jay Pscheidt, Department of Botany and Plant Pathology, Oregon State
University, Corvallis, OR; and Gary Chastagner, Washington State University, Western Washington Research and Extension
Center, Puyallup, WA.
a n d
Figure 1. A tanoak killed by Sudden Oak Death in Curry County, OR.
Phytophthora ramorum
SuddenOak
Death
EM 8877 • April 2006 • $2.50
2 Sudden Oak Death and Phytophthora ramorum
IntroductionNotsincewhitepineblisterrustwasintro-ducedaccidentallytotheNorthwest,nearly100yearsago,hasaforesttreediseasecausedsomuchturmoilinthewesternforestrycom-munity.EvenbeforePhytophthora ramorumwasdiscoveredinOregonin2001,diseasesurveyandmonitoringprogramswereinplace.Since2001,thepaceofsurvey,eradication,andcooperativeresearchcontinuestoacceler-ate,allwhilethepopularmediaandaninter-estedpublicanxiouslyawaitresults.
WhyareforesttreegrowersandforestresourcemanagersinthePacificNorthwestpayingsuchcloseattention?Because:
• SuddenOakDeathreadilykillsdominanttanoak,coastliveoak,andCaliforniablackoaktrees.
• Extensivetreemortalityalreadyhasdra-maticallyalteredforestlandscapes.
• Thediseasehasappearedinhorticulturalnur-seriesandgardencentersandcanbemovedlongdistancesquicklyviainfectedplants.
• Thecausalagenthasabroadhostrangeofmorethan100speciesinseveralplantfami-lies,andmanysusceptibleforestspeciesgrowfromCaliforniatoBritishColumbia.
• Thediseasecanspreadfromplantsintheunderstorytonearbytreesandfromtree
crownstoplantsontheforestfloor.
• Economicallyandecologi-callyvaluableconifers,includingDouglas-fir,coastredwood,andtruefirs,areonthehostlist.
• State,national,andinter-nationalquarantineshavebeenimposed.Allhostplantspeciesgrowninaffectedareasareregulated.
• HorticulturalnurseriesinOregonandWashington,aswellasinCalifornia,havelostmillionsofdollarsfromdestructionofinfectedstockandlossofmarkets.
• Activitiesrangingfromtimberharvesttocollectingwildgreens,andfromgrowingChristmastreestomanagingforest-treenurseries,couldbeaffected.
Some historyUnprecedentedlevelsoftanoak(Lithocar-pus densiflorus)andcoastliveoak(Quercus agrifolia)mortalitywerenotedfirstinMarinCounty,CAintheearlytomid-1990s.Localresi-dentscoinedthephrase“SuddenOakDeath”todescribetheapparentlyrapidtreemortalitytheyobserved.Thecausewasthenunknown.In2000,anewspeciesofPhytophthora,afungus-likewatermoldofunknownorigin,wasisolatedfromcankers(localizedareasofdeadcambium)ondyingtreesandlaterwasfoundtobethecausalagent.Soonitwasrecognizedthatthesamepathogenwascaus-ingleafblight,stemcankers,andtipdiebackonnursery-grownrhododendronsandvibur-numsinEurope.ThenewspecieswasnamedPhytophthora ramorumin2001.WiththeEuropeanconnection,attentioninCaliforniaturnedtoplantnurseriesinaffectedareas,anddiseasedrhododendronplantssoonwerefoundinseveralnurseries.
In2001,P. ramorumwasdetectedinCurryCounty,inextremesouthwesternOregon,ontanoak,Pacificrhododendron(Rhododendron macrophyllum),andevergreenhuckleberry(Vaccinium ovatum).Ninediseasecenters,rangingfrom0.5to11acresandtotalinglessthan40acres,werefoundintanoakforestsinaruralresidentialarea,onprivateforestindustryland,andonfederallandadministeredbytheU.S.DepartmentofInteriorBureauofLandManagement.TheOregonDepartmentofAgricultureimmediatelyquarantineda9-square-milearea.Infectedandsurroundingplantmaterialindiseasecenterswascut,piled,andburnedinacontinuingprogramtoeradi-catethepathogen(Figures2and3,atleft).
InMay2003,P. ramorumwasdiscoveredinawholesalehorticulturalnurseryinClackamasCounty,ORonPieris, Viburnum,andRho-dodendron;inJune2003,P. ramorumwasreportedonrhododendronandotherhostsataretailoutletinWashingtonStatethatwas
Figure 2 (below). An aerial view of tanoak trees killed by Phytophthora ramorum in Curry County, OR. Note the orange-red crowns of recently killed trees.
Figure 3 (at bottom). The same site after eradication treatment.
Sudden Oak Death and Phytophthora ramorum 3
affiliatedwiththeClackamasnursery.Aninternationalshipmentofrhododendronswasthesuspectedsourceofcontaminationinthoseincidents.Thatsamemonth,infectedcamelliasshippedfromCaliforniawerefoundinotherOregonnurseries.InMarch2004,itwasdeter-minedthatinfectedcamelliasfromanotherlargewholesalenurseryinsouthernCaliforniahadbeenshippedthroughouttheUnitedStatesandCanada,includingtoOregon,Washington,andBritishColumbia.Nationwide,stateandfederalagenciescontinuetotrack,confirm,anddestroyinfectedplantsandtosearchfornewinfectionsinlandscapesandforestareassurroundingintro-ductionsites.
Distribution and damage CurrentlyinCaliforniaP. ramorumisfoundinforestorwoodlandenvironmentsin14coastalcountiesfromMontereyCountyinthesouthtoHumboldtCountyinthenorth(Figure4).Mor-talityofcoastliveoakandtanoakcontinuesthroughouttheaffectedarea.Notallstandsareaffected;in2004,mortalitywasparticularlyintenseintheBigSurarea,southofMonterey,andin2005attentionwasfocusedonanout-breakinsouthernHumboldtCounty.
Hundredsofthousandsofcoastliveoak,tanoak,andCaliforniablackoaktreeshavebeenkilledbyP. ramoruminCalifornia.Thousandsofhazardousdeadtreeshavebeenremovedfromcampgrounds,privateproperty,androadsides.High-valuetreeshavediedinparksandbackyards,changingaestheticsandreducingpropertyvalues.Extensiveareasofmortalityhaveledtoconcernsaboutincreasedfirehazard,particularlyinthewildland–urbaninterfaceandinmunicipalwatersheds.Scien-tistsarestudyingtheshort-termimpactsonavarietyofwildlifespeciesforwhomthelossofoaksmeanslossoffoodandhabitat.NativeAmericanslivinginornearinfestedareasareconcernedaboutthedirecteffectofoakmortalityontheirfood-gatheringtraditionsandabouthowdamagetootherhostsmightimpacttraditionalactivitiessuchasberrypickingandbasketmaking.
Figure 4. Distribution of Sudden Oak Death as of December 12, 2005. Red triangles are confirmed isolations of Phytophthora ramorum; counties in darker yellow have P. ramorum confirmed in wildland. Data from California Department of Food and Agriculture and pathologists at the University of California, Davis and Berkeley campuses. California host data from CAL GAP Analysis Project. Oregon host data from OR GAP Analysis Project. Nursery confirmations are not depicted. Map by UCB CAMFER, http://kellylab.berkeley.edu/SODmonitoring/
4 Sudden Oak Death and Phytophthora ramorum
InOregon,newinfestedforestsiteshavebeendetectedinCurryCountysince2001(Figure5andTable1).MostofthenewfindsinOregonhavebeenadjacenttooldersites,althoughafewtreeshavebeeniden-tifieduptoamileawayfromprevi-ousinfections.TanoakistheonlyspeciesbeingkilledbyP. ramoruminOregon,althoughwildrhododendronandevergreenhuckleberrysufferdie-back.ArecentfindofdiseasewithinafewhundredyardsofthecurrentboundaryhasresultedinexpansionoftheCurryCountyquarantineareainFebruary2006.Theeradicationeffortcontinues.
Long-termimpactsofSuddenOakDeathatthewatershedorforestecosystemlevelarehardtopredict.Changesinforestcoverresultinchangesinmicroclimates,influenc-ingspeciescompositionandforestsuccession.Thelossofasinglespe-ciesormoresubtleshiftsinspeciescompositionmayhaveprofoundeffectsinthedecadesahead.
NurseriesontheWestCoasthavebeensurveyedforthedisease,andseveralhavebeenfoundinfested.Whenfound,infectedplantsandtheirneighborshavebeendestroyedandadjacentenvironssurveyedforP. ramorum.
InEurope,P. ramorumhasbeenwidelydis-persedthroughthenurserytradeandinsomelocationshasbecomeestablishedinwoodlandsettings.Itisinnurseries,gardencenters,or
Table 1. Eradication progress in Curry County, Oregon.
2001 2002 2003 2004 2005
New SOD trees 91 85 49 30 49*
Acres treated 40 8 12 10 18*
Quarantine area (square miles)
9 9 11 11 21.5**
* as of December 2005 ** as of February 2006
somelandscapeplantingsin15countries.ThemostcommonhostsareRhododendron, Vibur-num,andPieris,butitalsohasattackedmaturelandscapetrees,includingNorthAmericanredoakandsomeotheroakspecies,beech,andhorsechestnut.ThenativeoaksofnorthernEurope,inthewhiteoakgroup,havenotbeenaffected.Europeancountriesareattemptingtostopfurtherspreadofthepathogenandtoeradicateitfromthenurserytrade.InEngland,wherespreadfromunderstoryrhododendronstonearbytreeshasbeenobserved,scientistsareattemptingtoeradicatethediseasefromthefewparksandwildlandswhereitisestab-lished.TheyareusingmethodssimilartothoseusedinOregon.
Figure 5. Distribution of P. ramorum in Curry County, OR, and the bound-ary of the regulated area (red lines) as of February 2006.
Brookings
Sudden Oak Death and Phytophthora ramorum 5
monitoraswellasthecostsoftheregulatoryanderadicationefforts.
Lossestodatecouldbedwarfedifthediseasespreadsnorthwardandimpactsconiferproduc-tionareas.Eventhoughcurrentknowledgesug-gestsDouglas-firandcoastredwoodareunlikelytosufferseriousgrowthlossormortality,theeconomicimpactofquarantineregulationsaffectingtradeinconiferandhardwoodprod-ucts,logs,Christmastrees,andtreeseedlingscouldbegreat.
The pathogenPhytophthora ramorumisanOomycete,awatermoldthatlookslikeafungusbutismorecloselyrelatedtosomemarinealgae.MostPhy-tophthoraspeciesarerootpathogens,but
ThereisgreatconcernaboutthevulnerabilityoftheoakforestsoftheeasternUnitedStatestoP. ramorum (Figure6).LaboratorytestsandexperienceintheUnitedKingdomindicatethatnativeredoakspeciesareatrisk.Inthousandsofacresofforest,understoryhostcompositionandclimatemaybesimilarenoughtoaffectedareasinCaliforniaandOregonthatthediseasecouldbecomeestablished.TherecenttransportofthepathogenonnurserystockfromWestCoastnurseriestoeasternstatescausedgreatalarmandtriggeredintensiveeffortstofindanddestroyinfectedplantsintheeasternnurseriesandtosurveysurround-ingforestareasfordisease.TodatethereisnoevidencethatSuddenOakDeathhasbecomeestablishedineasternforests.
ThefulleconomicimpactofSuddenOakDeathhasnotbeentallied,butitwillbemanytensofmillionsofdollars.Directlossesaregreatestinthehorticulturalnurseryindustry,wherethousandsofplantshavebeendestroyedtostopthespreadofdisease.Furtherlossesfromdisruptedandlostmarketsalsomustbebornebytheindustry.Neithertanoaknorcoastliveoakisavaluabletimbertree,butinbothCaliforniaandOregonoutbreakareas,theamenityvalueoftreesaroundhomescanbegreat.Wealsomustincludethecoststoremovedeadtrees,todisposeoftheinfectivegreenwastesanitarily,andtosurveyand
Figure 6. Predicted vulnerability of forests in the United States to Phytophthora ramorum, based on presence of potentially susceptible vegetation, favorable climate, and likely pathways. Map by USDA Forest Service.
Relative risk High Moderate Low
6 Sudden Oak Death and Phytophthora ramorum
Phytophthora ramorumaffectsabovegroundplantparts.P. ramorumiswelladaptedtothemild,wetconditionsofthePacificNorthwest.Thepathogenformssporangia(sacsofspores)oninfectedleavesortwigs(Figure7).Thesporangiaarespreadinwindandrainandcanreleaseswimmingzoosporesiftheylandonawetsurface.Thezoosporesgerminateandinfecttheplant,startinganewinfection.Phy-tophthora ramorumalsomakesthick-walledrestingspores(chlamydospores)ininfectedplantparts,whichallowittosurviveheatanddroughtandtopersistformonthsinsoiland
plantdebris(Figure8).
Inaddition,P. ramorum hastwomatingtypes,desig-natedA1andA2.Sexualspores(oospores)formiftheoppositematingtypesjoin.OnlytheA2matingtypehasbeenfoundintheforestsofCaliforniaandOre-
gon,whileonlytheA1matingtype(withasingleexception)hasbeenfoundinEurope.Thissug-geststhattheNorthAmericanforestepidemicdidnotoriginateinEuropeandviceversa.Pre-sumablythisdiseasespreadfromsomeunknownplacein
theworldwherebothmatingtypesarepres-ent.BothmatingtypeshavebeenisolatedfromNorthwestnurseries,however,suggestingatleasttwointroductionsintothenurserytrade.Todate,noevidenceofsexualrecombinationhasbeenfoundinnurseriesorforests,butthethreatofnewracesofthepathogenaddsonemorereasontohaltintroductions.
Recently,athirdgenetictypeofP. ramorum.wasfoundinaWestCoastnursery.ItistheA2matingtypebutisgeneticallydistinctfromthefungusasknownfromeitherEuropeorNorthAmerica.ItmayprovideimportantcluestotheoriginandevolutionaryhistoryofP. ramorum.
Spread of Phytophthora ramorumIntheforest,thepathogenspreadsfromtreetotreeaszoosporesorsporangiainwater:viarainsplash,dripandstemflow,andwind-drivenrain.Tanoaktwigsandleavesareinfectedfirstintheuppercrown.Newgrowthinspringismostsusceptible.Zoosporesswimthroughwaterfilmsonthesurfaceofleavesorstems,thensettle,germinate,andpenetratetheplant.Newsporangiaareformedoninfectedleavesandtwigsinwetweather(Figure7)andmaywashorsplashdownthestem.Thetrunkcankersthatkillthetreeapparentlyoriginatefromsporeswashedfromabove.Rhododen-dronsandhuckleberries,andoccasionallyotherhostsgrowingbeneathinfectedtrees,maybeinfected.Meanwhile,dislodgedsporangiafromtheuppercrowninfectionsalsomaybecarriedbythewindtodistanttrees.Halfofnewlyinfectedtreesarefoundwithinabout300feetofpreviouslyinfectedtrees,apatternconsis-tentwithwindandraindispersal.
Infectedleavesdroptotheground,andmanysporeslandonthesoil.Infestedsoilandleavescanbetransportedonboots,vehicles,andanimals,especiallyinwetweather.Sporescanbesplashedbackuponlow-hangingfoliageandthereinitiatenewinfections.NaturalrootinfectionhasbeenobservedinCaliforniaforestswherethesporeloadisveryhigh.Phytophthora ramorumalsoisfoundinstreamsdraininginfestedareas,althoughnonewforestinfectionshavebeentracedtostreams.Irrigationwaterdrawnfrominfestedstreamsorotherwatersourcescanstartnewinfections.
NotallhostsareequalwhenitcomestospreadingP. ramorum.ItisbelievedthatwoodandbarkofoaksproducefewP. ramorumspores,whileleafsurfaces,particularlyonOregonmyrtlewood(alsoknownasCalifor-niabaylaurel),areexcellentsporeproductionfactories.Understoryplantsmayplayaveryimportantroleinhowthediseaseismaintainedandspreadwithinagivensite.
Todate,extensiveP. ramorumwildlandinfes-tationshavebeenreportedinforestcommuni-tieswithknownassociatedepidemiologicallyimportanthosts(sporefactories)suchas
Figure 7. Closeup of a Phytophthora sporangium releasing swimming spores (zoospores) in water. Photo courtesy of Fred Schwenk, Kansas State University.
Figure 8. Sporangia and round chlamydospores (resting spores) of P. ramorum formed when an infected Oregon myrtlewood leaf was placed in water.
Sudden Oak Death and Phytophthora ramorum 7
tanoak(CaliforniaandOregon),Californiabaylaurel(California),and/orcoastredwood(California).CurrentlyitisnotknownwhetherotherhostscanproducesporeloadscapableofsustainingP. ramorumandassociateddiseasesinregionsofthePacificNorthwestoutsidethenativerangeoftanoak,Californiabaylaurel,orcoastredwood.
Phytophthora ramorumalsoismovedlongdistancesininfectednurserystock.Plantsmayshownosymptomsoronlycrypticindicationsofinfectionatthetimeofsale.SomefungicidesthatareusedroutinelyinnurseriessuppresssymptomsofPhytophthorainfection,butthepathogensurvivesandmaybecomeactiveagain
Figure 9 a
Figures 9 a–f. Two symptoms of P. ramorum on tanoak:(9 a–c) bleeding on bark surface; and(9 d–f) mottled discoloration of inner bark.
Figure 9 c
Figure 9 d
Figure 9 e
Figure 9 f
Figure 9 b
inafavorableenvironmentasthechemicalwearsoff.
Diseases caused by Phytophthora ramorumPhytophthora ramorumaffectsdif-ferentplantspeciesindifferentways(Table2).Notallaffectedspeciesarekilled;somesuffertipandshootdiebackwhileothersexperiencerela-tivelyharmlessleafspotting.SuddenOakDeathontreesintheoakfamilyischaracterizedby“bleeding”cankersthatgirdlethetrunksoftanoaks(Figures9a–f)andsomeotheroakspecies.
Table 2. One pathogen, three diseases.
Disease Symptoms Hosts
Sudden Oak Death Bleeding cankers;tree death.
Oak, tanoak
P. ramorum shoot blight
Shoot tip dieback. Coast redwood, Douglas-fir, evergreen huckleberry, true fir hosts, Pacific madrone, Pacific yew, rhododendron, tanoak
P. ramorum leaf blight
Petiole and midrib necrosis; leaf spots on edges or leaf tips; leaf spots with margins that look water soaked.
Cascara, myrtlewood, rhododendron, tanoak
8 Sudden Oak Death and Phytophthora ramorum
AmbrosiabeetlesandsapwooddecayfungisuchasHypoxylon thouarsianumoftenareassociatedwithinfectedtrees,hasteningdeath(Figures10a–b).Onrhododendron,evergreenhuckleberry,Pacificmadrone,Douglas-fir,truefirhosts,andcoastredwood,thediseaseischaracterizedbyleafblightandshootdiebackandismoreappropriatelycalledPhytophthora ramorumshootblight(Figure11andFigures12a–c).Theleafpeti-oleandmidribmaybediscolored,ortheleaftiporentireleafblademaybenecrotic(Figure13).Leafspotsoftenoccurwherewater
Figures 10 a–b. Ambrosia beetles, as evidenced by characteristic boring dust (at left above) and sapwood decay fungi Hypoxylon thouarsianum (above right) often are associated with P. ramorum-infected oaks.
Figure 11. Symptoms of P. ramorum infection on shoot tips of Douglas-fir.
Figures 12 a–c. Shoot dieback symptoms of P. ramorum on evergreen huckleberry (above), rhododendron (at right), and tanoak (at far right).
Figure 13 (at right). Blackened petioles and midribs are typical symptoms of P. ramorum on tanoak leaves.
Sudden Oak Death and Phytophthora ramorum 9
accumulatesontheleafmargins.Shootsdiebackwhenthediseaseissevere.Ontanoak,Douglas-fir,truefirhosts,andcoastredwood,smalltwigs,sprouts,andnewshootsareaffected(Figure11,Figure12c,andFigures14a–c);succulentstemsdrooporbecomecrooked,symptomssimilartothoseoffrostdamage.Otherhosts,suchasOregonmyrtlewoodorcascara,maybeinfectedbutshowonlysubtlesymptoms,suchasyellowtipsonthelowerleaves(Figure15).Because
Figures 14 a–c. Symptoms of P. ramorum on coast redwood (at far left) and grand fir (at left). Note sprout dieback and dead needles on coast redwood and (below, left) dieback of grand fir leader.
Figure 15 (above). Symptoms of P. ramorum on Oregon myrtlewood (California bay laurel).
Oregonmyrtlewoodlosesitsolderleavesinearlysummerafternewleavesemerge,whetherinfectedornot,symptomaticleavesmaynotbereadilyavailableforinspection.
Ingeneral,symptomscausedbyP. ramorumaresimilartosymptomscausedbyotheragents,inparticularotherPhytophthoraspe-cies.DiagnostictechniquessuchasculturingorDNAanalysisarecriticalforidentifyingthispathogen.
10 Sudden Oak Death and Phytophthora ramorum
Hosts and symptomsThehostlistforPhytophthora ramorumislargeandgrowingandincludesmanyspeciescommonlyfoundinPacificNorthwestforests(Table3).Forregulatorypurposes,theAnimalandPlantHealthInspectionServiceoftheU.S.DepartmentofAgriculture(USDAAPHIS)maintainstwoofficialhostlists.Onelistisofconfirmed host species:plantsthathavebeeninfectednaturallyinforestsornurseriesandwhosesusceptibilityhasbeenprovenbyacceptedscientificmethods.Theotherlistisof“associated” host species:thatis,plantsthathavebeennaturallyinfectedbutonwhichtestingisnotyetcomplete.Theassociated-hostlistincludessomeimportantwesternwildlandspeciessuchaswhitefir,grandfir,redfir,and
Table 3. Western woodland confirmed host species of Phytophthora ramorum. Additional host species are known from nurseries and from Europe.
Plant species Common name and location1 Symptoms
Lithocarpus densiflorus tanoak OR, CA Bole cankers, death
Quercus agrifolia coast live oak CA Bole cankers, death
Quercus chrysolepis canyon live oak CA Bole cankers, death
Quercus kelloggii California black oak CA Bole cankers, death
Quercus parvula var. shrevei Shreve oak CA Bole cankers, death
Arbutus menziesii madrone CA Shoot dieback
Arctostaphylos manzanita manzanita CA Shoot dieback
Pseudotsuga menziesii Douglas-fir CA Shoot dieback
Rhododendron macrophyllum Pacific rhododendron OR Shoot dieback
Sequoia sempervirens coast redwood CA Shoot dieback
Taxus brevifolia Pacific yew Shoot dieback
Vaccinium ovatum evergreen huckleberry OR, CA Shoot dieback
Acer macrophyllum bigleaf maple CA Leaf blight
Adiantum aleuticum western maidenhair fern CA Leaf blight
Adiantum jordanii California maidenhair fern CA Leaf blight
Aesculus californica California buckeye CA Leaf blight
Frangula (Rhamnus) californica California coffeeberry CA Leaf blight
Frangula (Rhamnus) purshiana cascara CA, OR Leaf blight
Heteromeles arbutifolia toyon CA Leaf blight
Lonicera hispidula California honeysuckle CA Leaf blight
Rosa gymnocarpa wood rose CA Leaf blight
Trientalis latifolia western starflower CA Leaf blight
Umbellularia californica Oregon myrtlewood ORCalifornia bay laurel CA
Leaf blight
1 CA = California, OR = Oregon
vinemaple.Foranup-to-datelistofconfirmedhostsandassociatedspecies,seehttp://www.aphis.usda.gov/ppq/ispm/pramorum/
InadditiontotheAPHISlists,laboratorytestsusingartificialinoculationindicatethatmanymoreplantspecies,bothwildandcultivated,aresusceptibletoP. ramorum, butthesespeciesarenotregulatedbecausetheyhavenotbeenfoundnaturallyinfected.Artificialinoculationuseshighsporeloadsandoptimumenvironmentsforinfection.
InCaliforniaforestswhereinfectionlevelsareveryhigh,moreunderstoryspeciesareinfectedthaninOregonforestswherethesporeloadiskeptverylowbytheeradicationprogram.
Infection of conifersSusceptibilityofconiferhostsdeservesspecialmentionbecauseoftheirimportanceinPacificNorthwestforests.NonaturalinfectionofanyconiferhasbeenobservedinOregonorWashington.InCalifornia,however,Douglas-fir,redfir,grandfir,whitefir,coastredwood,andPacificyewareinfectedwhengrowingbeneathinfectedoaksandCaliforniabaylaurel(Figure11andFigures14a–c,pages8and9respec-tively).Inoculationstudiesindicatethatotherconifers,especiallyAbiesspecies,aresusceptibleandmaybedamagedifexposedtohighinoculumlevels.
Infectionoccursinspringthroughbudscarsatthebaseofnewgrowth;onlyfoliageandtwigsareaffected(Figure11andFigures14a–c,pages8and9respec-tively).ThedamageonDouglas-firandtruefirhostslooksmuchlikeinjuryfromalatefrostorBotrytistipblight.Repeatedinfectionmaykillseedlingsandsaplingsorgreatlyaltertheirgrowth.Similarly,onlythefoliageandsmall-diametersproutsofcoastredwoodhavebeenfoundinfected.BecausetrunkcankershavenotyetbeenfoundonDouglas-firandcoastredwood,onlynurserystock,foliage,andmaterialslessthan1inchdiameter(suchassproutsandshoots)areregulated,notlogsorlum-ber.Truefirhosts,currentlyontheassociated-hostslist,areregulatedasnurserystockatthistime.
Sudden Oak Death and Phytophthora ramorum 11
Stopping Sudden Oak DeathManagementeffortsinPacificNorthwestforestsandnurseriesfocusoneradicatingthepathogenwhereitisfoundandonprevent-ingnewinfections.InCalifornia,wherethediseaseismoreextensive,a“slowthespread”strategyisinplace.Earlydetectionisvitaltopreventingdiseasespread.PracticesusefulinmanagingotherfoliarPhytophthoradiseasesinnurseriesalsowillhelpprotectplantsfromP. ramoruminfection.
Detection surveysSeveral P. ramorumdetectionsurveysareconductedeachyearinat-riskforestareasbytheOregonDepartmentofForestry(ODF)andtheUSDAForestService.Theforestrangeoftanoakissystematicallysurveyedfromafixed-wingaerialsurveyplane,andsuspicioustreesaremapped.Afollow-uphelicoptersurveyprovidesacloserlookforsymptomatictreesandenablesmoreprecisemapcoordinates.Allsuspecttreesarecheckedfromthegroundandsamplescollectedforconfirmationasappropri-ate.Inaddition,annualgroundsurveyschecktheperimetersofpreviouslytreatedareasfornewlyinfectedtrees.
Nurseries,Christmastreeplantations,andothersitesconsideredathighriskalsoaresur-veyedandsampledbytheOregonDepartmentofAgriculture(ODA)andtheWashingtonStateDepartmentofAgriculture(WSDA)withassistancefromUSDAAPHIS.IfP. ramorumisfoundinanurseryorothersite,theeradica-tionprotocolrequiresadditionalperimetersurveysinthesurroundinglandscapeplantingsandwildlands.
EradicationIfP. ramorumisfound,ODA,WSDA,andUSDAAPHISworkwiththelandownertopreventfurtherdiseasespreadandtoeradicatetheinfestation.Theagenciescontinuetomoni-torthesiteaftereradicationuntilithasbeenfreeofP. ramorumfor2years.TheUSDAhasdrafteduniformproceduresfordealingwithnursery,residential,andlandscapeinfestations.CheckthefinalregulatoryactionplanpostedontheODA,WSDA,andUSDAAPHISweb-sites(seelastpage)forup-to-dateinformation.
Nurseries and Christmas tree plantationsUndercurrentfederalregulations,nurser-iesandChristmastreeplantationsaretreatedsimilarly.Phytophthora ramorumhasnotbeenfoundinforest-treenurseriesorChristmastreeplantationsinOregonorWashington.Ithas
Everyone in the field should be on alertField-goingforestry,plantation,andnurseryper-sonnelshouldbeawareofthesymptomscausedby P. ramorum.SeveralguidestodiagnosingP. ramo-ruminfectionareavailableontheWeb.MasterGardeners,countyExtensionagents,andplantpathologistsinforestryandagriculturalagenciesthroughoutWashingtonandOregonarebeingtrainedtorecognizethesymptomsof P. ramorumandtobethe“FirstDetector”indiagnosis.Symp-tomscausedby P. ramorumareeasilyconfusedwiththosecausedbyotherPhytophthoraspeciesandotherplantpathogensandinsects.Positivediagnosiscanbemadeonlyusinglaboratorytechniques.
Figure 16. Tanoak mortality in the understory.
12 Sudden Oak Death and Phytophthora ramorum
beenfoundinChristmastreeplantationsinCalifornia,however,whereitaffectsDouglas-firandseveraltruefirspecies.
IfP. ramorumisfoundinNorthwestnurseriesorChristmastreeplantations,eradicationwillbeordered.Shipmentofhostandassociatedhostplantswillbeprohibiteduntiltheextentofinfectionwithinthesitehasbeendetermined.Allplantswithinablockthatcontainsinfectedplants,andsusceptibleplantswithin2metersofthatblock,willbedestroyedbyburningorburial.Healthy-appearinghostplantswithin10metersoftheinfestedblock(s)willbeheldforaperiodoftimetoobservesymptoms;fungicidetreatmentwillbeprohibitedduringthistimesothatsymptomswillnotbemasked.Soil,irrigationwater,andpottingmediaalsowillbetestedforP. ramorum.Additionaltreat-mentsmaybeorderedtodealwithinfestedsoilorcontainers.
Propertiesandnaturalizedareassurroundinginfestednurseriesalsowillbesurveyedfor
P. ramorum. Trace-backinvestigationswillbecon-ductedtodeterminethesourceofinfectedplants,andtrace-forwardinvestigationswillbeconductedifanyplantsfromtheinfestedblock(s)orfieldwereshipped.Shipmentofhostandassociatedhostplantsmayresumeaftertestsshowthediseaseisgone.Nurserieswillbetestedforatleastthenext2years.
InOregonandWashingtonhorticulturalnurseries,theeradicationprogramhasbeenlargelysuccessful.However,theimportationofnewinfectedstockfromoutofstateisacon-tinuingthreat.Shouldarecur-rentinfectionbefoundwithinanursery,amorestringenteradicationprotocolwill
likelybeenforced.
If you work in infested forest areas• Informyourcrewsthattheyareworkinginanareainfested
withP. ramorum.• Informthemthatunauthorizedcollectionortransportofhost
plantmaterialisprohibited.
• Providethemwithsanitationkitscontaining:chlorinebleachsolution(onepartbleachtoninepartswater)oraproductsuchasCloroxClean-up;ascrub-brush;ametalscraper;abootbrush;andplasticgloves.
• Useallreasonablemethodstosanitizepersonalgearandcrewequipmentbeforeleavinga P. ramorum-infestedsite.Scrape,brush,and/orhoseoffsoilandmudfromclothing,gloves,boots,andshoes(Figure17).Removemudandplantdebrisfromvehiclesandequipmentbysweeping,blowing,orpowerwashing.
• Whenpossible,workon P. ramorum-infestedsitesduringthedryseasonorduringdryspells.Whenworkinginwetcondi-tions,keepequipmentonpavedordrysurfaces.
• Workindisease-freeareasbeforeproceedingtoinfestedsites.
Figure 17. A forest pathologist washes his boots before he leaves the regulated area in Curry County, OR.
Sudden Oak Death and Phytophthora ramorum 13
Forest settingsStateofOregonregulationsmandatetheeradi-cationofPhytophthora ramorumwherefoundintheforestonstateandprivatelands.Infectedtreesarecutandburned,alongwithallhostplantsgrowingwithinatleast100feetormoreofinfectedplants.Herbicideshavebeenusedtoreducethelikelihoodofresproutingfrom
cutstumps(Figures18a–c).FederalforestryagenciesarecooperatingwithOregonineradicationeffortsandhavecompletedenvi-ronmentalanalysesforeradicationactivitiesonfederallandswhennecessary.ODAcontinuestomonitornewgrowthandsoilontheeradica-tionsites.Sofar,about88forestacreshavebeentreatedinCurryCounty.
Figures 18 a–c. Infected tanoak is burned on a site in Curry County, OR (above left and right). After the burn (left), the site’s alders remain.
14 Sudden Oak Death and Phytophthora ramorum
PreventionThegreatestriskofspreadingP. ramorumtonewareasintheNorthwestisthroughmove-mentofinfectedplantsorplantparts.Ifinfectedplantsaretransportedtoareaswithhostsandasuitableenvironment,thepathogenwilllikelybecomeestablishedovertime.Alwaysbesureofthesourceandhealthofyourplantingstock.Ifpossible,purchaseplantingstockthathasbeencertifiedasP. ramorum-freethroughanofficialinspectionandcertificationprogram.P. ramorumalsosurvivesinandcanbespreadviamovementofinfestedsoilandwater.
Prevention and suppression with fungicidesMostconventionalfungicidesarenoteffec-tiveagainstPhytophthoraspeciesbecausethespeciesarenottruefungi.SeveralclassesofcompoundsareactiveagainstPhytophthoras,however.Carefullyused,thesecanbeusefulinprotectingplantsagainstinfection.Theyseldomkillthepathogen,however,iftheplantisalreadyinfected.Instead,theymaymasksymptomdevelopmentandleadtoinadvertenttransportofinfectedstockandspreadofthedisease.Oncechemicalactivityhassubsided(about3to6months),Phytophthoracanresumegrowthwithininfectedplants.Thisiswhyplantsfromothernurseriesmustbeheldforseveralmonthstoseewhethersymptomsbecomeevident.
Forspecificfungicides,consultthelatestedi-tionofthePNW Plant Disease Management Handbook(seethelastpageofthispublicationfororderinginformation)orvisitAnOnlineGuidetoPlantDiseaseControlat:http://plant-disease.ippc.orst.edu/index.cfm.
Protecting yourself ForestresourcemanagersinthePacificNorth-westneedtobealertforinadvertentintro-ductionsofthispathogen,especiallywhenimportingmaterialfromareaswithknowninfestations.Managersalsoneedtobeawareoftheregulationsonmovinghostmaterial.Regulationshelpslowspread,butcommonsenseisyourbestprotection.
Transporting plant materialDonottransportoakfirewoodorotherpoten-tiallyinfectedplantmaterialsfrominfestedareasinCaliforniaandOregontootherareas.
Visiting infested areasIfyouvisitinfestedareas,washyourvehicleandshoesandremoveleaflitterandotherplantdebrisfromvehicles,otherequipment,andclothingbeforetravelingtodisease-freeareas.
Importing nursery stockInOregon,ifimportingnurserystockofhosttreesorshrubsfromanysource(outofstateorinternational),youmustnotifytheNurs-ery&ChristmasTreeProgramSupervisorattheOregonDepartmentofAgriculturebyfax(503-986-4786)orbye-mail([email protected]).PlantsmustbecertifiedasbeingfreefromP. ramorum.FurtherinformationonOregon’simportregulationsisonlineathttp://egov.oregon.gov/ODA/PLANT.
InWashington,ifimportinganyhostplantsyoumustbeincompliancewiththeWashing-tonnotificationruleandnotifytheNurseryInspectionSupervisorinOlympiabyfax(360-902-2094)ore-mail([email protected]).Furtherinformationisavailableonlineathttp://agr.wa.gov/PlantsInsects/Diseases/SOD/.
Illegalimportationsmayresultinsignificantfines.USDAquarantineregulationspertainingtoP. ramorumareonlineathttp://www.aphis.usda.gov/ppq/ispm/pramorum.
Sudden Oak Death and Phytophthora ramorum 15
Learning the range of symptomsFamiliarizeyourselfandyourstaffwiththerangeofsymptomscausedbyP. ramorum.Checkyourplantsoften.DiseasescausedbyotherPhytophthoraspeciescancausesimilarsymptoms.
IfyoususpectP. ramorum,contacteithertheOregonDepartmentofAgriculture’sInvasiveSpeciesHotline,1-866-INVADER,ortheWashingtonStateUniversityplantdiseasediagnostician,1-253-445-4582.
Forquestionsrelatedtobackyardorwoodlandplants,theOSUorWSUExtensionofficeinyourcountyand/orMasterGardenersinExten-sionofficescanassistwithidentification,orlocalUSDAForestServiceofficescanputyouincontactwithappropriatediagnosticexperts.
Diagnosis,usingseveraltechniques,maytake1to2weeksoruptoamonthormore.While waiting for the diagnosis, do not move or ship symptomatic plants or any nearby plants.Evenifthelatterlookhealthy,theymaybecontaminated.
Bealertforsymptomsonanyshrubandtreespecies,notjustthoseonthelistofhostsandplantspeciesassociatedwithP. ramorum.
Ifyourbusinessisconifernurserystock,Christmastrees,orforestproducts,don’tbringornamentalplantsnearyourproductionareas.AninfectedrhododendronplantedasanornamentalwilltriggerinspectionandholdsonyourconiferstockasquicklyasaninfectedDouglas-fir.
Quarantines and regulationsStateandfederalregulatoryactionshavebeenimplementedtohelppreventthemovementofinfestedwood,bark,forestgreeneryandotherwildmaterial,soil,andhostnurserystockfrominfestedareas.Atthistime,21.5squaremilesofforestinCurryCounty,ORaresubjectto
thisregulation.ForcurrentinformationonquarantinesandotherSuddenOakDeathregu-lations,visittheODAwebsiteathttp://egov.oregon.gov/ODA/PLANT,theWSDAwebsiteathttp://agr.wa.gov/PlantsInsects/Diseases/SOD/,andtheUSDAAPHISwebsiteathttp://www.aphis.usda.gov/ppq/ispm/pramorum.
InadditiontoUSDAAPHISregulations,severalforeigncountrieshaveimposedquar-antinesonmovementofhostmaterialsfrominfestedareasinCalifornia,Oregon,andWashington.Theserestrictionscoverhorticul-turalandforestnurserystock,Christmastrees,andinsomecaseslogsandlumber.
Inspection and certification USDAAPHISadoptedaFederalOrderonDecember21,2004,thatrequiresallnurseryandplantingstockfromCalifornia,Oregon,andWashingtontobeinspectedandcertifiedfreeofP. ramorumpriortoexportfromthesestates.
AllnurseriesexportingplantmaterialmustbevisuallyinspectedforP. ramorum.
GrowersofhostorassociatedhostplantstockmusthavetheirplantstestedforP. ramoruminadditiontothevisualinspection.
Moreinformationaboutthisprogramisavail-ableonlineathttp://www.aphis.usda.gov/ppq/ispm/pramorum.
Oregonhasadoptedasimilarregulationfornurseryandplantingstockgrownforexportandforsalewithinthestate.ListsofnurseriesparticipatingintheinspectionandcertificationprogramareavailableonlinefromtheOregonDepartmentofAgriculture(http://egov.oregon.gov/ODA/PLANT)andtheWashingtonStateDepartmentofAgriculture(http://agr.wa.gov/PlantsInsects/Diseases/SOD/).
Trade-nameproductsandservicesarementionedasillustrationsonly.ThisdoesnotmeanthattheOregonStateUniversityExtensionServiceeitherendorsestheseproductsandservicesorintendstodiscriminateagainstproductsandservicesnotmentioned.
©2006OregonStateUniversity
ThispublicationwasproducedanddistributedinfurtheranceoftheActsofCongressofMay8andJune30,1914.ExtensionworkisacooperativeprogramofOregonStateUniversity,theU.S.DepartmentofAgriculture,andOregoncounties.
OregonStateUniversityExtensionServiceofferseducationalprograms,activities,andmaterials—withoutdiscriminationbasedonrace,color,reli-gion,sex,sexualorientation,nationalorigin,age,maritalstatus,disability,ordisabledveteranorVietnam-eraveteranstatus.OregonStateUniversityExtensionServiceisanEqualOpportunityEmployer.
For more informationOregonStateUniversityExtensionService
SODwebsitehttp://extension.oregonstate.edu/emergency/oak_death.php
TheExtensionServicesofOregonStateUni-versity,WashingtonStateUniversity,andUniversityofIdaho.AnOnlineGuidetoPlantDiseaseControlhttp://plant-disease.ippc.orst.edu/index.cfm
Pscheidt,J.W.andC.M.Ocamb,eds.PacificNorthwestPlantDiseaseManagementHandbook(revisedannually).Corvallis,OR:ExtensionServicesofOregonStateUniversity,WashingtonStateUniversity,andUniversityofIdaho.Orderformforprinteditiononlineathttp://extension.oregonstate.edu/catalog/orderform.pdf
CaliforniaOakMortalityTaskForcewebsitehttp://suddenoakdeath.org/
Davidson,J.M.,S.Werres,M.Garbelotto,E.Hansen,andD.MRizzo.2003.SuddenOakDeathandassociateddiseasescausedbyPhytophthora ramorum.PlantHealthProgress,PlantManagementNetworkInternational.http://www.plantmanagementnetwork.org/pub/php/diagnosticguide/2003/sod/
OregonDepartmentofAgriculturewebsitehttp://egov.oregon.gov/ODA/PLANT
USDAAnimalandPlantHealthInspectionService(APHIS),PestDetectionandMan-agementPrograms,InvasiveSpeciesandPestManagement:SuddenOakDeathhttp://www.aphis.usda.gov/ppq/ispm/pramorum
WashingtonStateDepartmentofAgriculturewebsitehttp://agr.wa.gov/PlantsInsects/Diseases/SOD/
PublishedApril2006
Information on Sudden Oak Death is constantly changing. Be sure to
check online sources regularly.
