Dramaticneedlebrowningandcanopydiebackofeasternwhite
pine(Pinusstrobus)insouthernNewEngland
NicholasJ.Brazee,Ph.D.
ExtensionPlantPathologist Duringthespringof2016,adramaticdeclineofeasternwhitepine(Pinusstrobus)hasbeenobserved
throughoutsouthernNewEngland.Needlesofmaturetreesbecomestraw‐coloredtobrownbeforethey
areprematurelyshedfromthecanopy.Insomecases,onlyafewmainbranchesaresymptomaticwhereas
onothertrees,theentirecanopyexhibitsthesymptoms(Fig.1).Onefeatureofthedeclineisthatdespite
significantneedlebrowningandprematuresheddinginthecanopy,thecurrentseason’sneedlesare
elongatingandappearhealthy(Fig.2).
FIGURE1.EASTERNWHITEPINEONTHEUMASSCAMPUSWITHEXTENSIVENEEDLEBROWNINGANDPREMATURE
SHEDDINGTHATDEVELOPEDINSPRINGOF2016.
FIGURE2.DEVELOPINGCANDLES(BRANCHLETS)WITHCLUSTERSOFMALECONESAREABUNDANTWHILEOLDER
NEEDLESBECAMEBROWNANDWEREPREMATURELYSHED.
Basedonobservationsfromarborists,landscapersandhomeownersmadetotheUMassPlant
DiagnosticLaboratory(UMPDL),whitepinedeclineseemstobeespeciallysevereinsoutheasternNew
Hampshire,easternMassachusettsandeasternConnecticut.Thecauseofthisdramaticdeclineeventisnot
entirelyunderstood,asthereareseveralinteractingstressesthatmustaccountedfor.However,needle
blightpathogenshavebeenaprimaryissueaffectingwhitepinesinceapproximately2010.Recentstudies
haveidentifiedseveralfungalpathogensareresponsibleforwhitepineneedleblightinNewEngland
(Brodersetal.2015,WykaandBroders2016).Fourneedleblightfungiinparticularhavebeenidentified
astheprincipalpathogensassociatedwithwhitepineneedleblightintheregion(Wykaetal.2016)and
include:
1. Lecanostictaacicola(formerlyMycosphaerelladearnessii)
2. Lophophacidiumdooksii(formerlyCanavirgellabanfieldii)
3. Bifusellalinearis
4. Septorioidesstrobi
BasedonsamplessubmittedtotheUMPDL,threeofthesefourpathogenshavebeenregularlyfound
onwhitepineswithsymptomsofneedleblight(Lophophacidiumhasbeenuncommontodate).Evidence
nowsuggeststhereisastronglinkbetweenclimatechangeandtheincreaseindamagefromneedleblight
pathogensofwhitepine.Usingregionalweatherdata,Wykaetal.(2016)determinedthatanincreasein
precipitationduringthemonthsofMay,JuneandJuly—thetimeperiodwhenwhitepineneedlesare
elongating—ispositivelycorrelatedwithdamagefromneedleblightpathogens.However,asisthecase
withmanyconiferneedlepathogens,thateffecthasaoneyeardelay.Forexample,above‐average
precipitationbetweenMay–Julyin2016wouldcorrelatetohigherdiseasepressurein2017.
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Therefore,wemustgobacktothegrowingseasonof2015tobetterunderstandwhatfactorsmight
beinfluencingthedamagedobservedthisyear.Duringthespringof2015,Maywasextremelydrywith
above‐averagetemperaturesandbelow‐averageprecipitationwasalsorecordedfromJulythrough
Septemberintheareaswherewhitepinedeclineappearstobethemostsevere(Fig.3).June,incontrast,
wasverywetandthereweremultiplerainstormswithaccumulations>0.75″(Fig.4).Heavyrainspromote
sporulationanddispersesignificantvolumesofneedleblightpathogensporesthroughsplashingand
runningwater.Despitetheabove‐averagerainfallinJune,therestofthegrowingseasonwasfairlydryand
manytreesmayhaveenteredthedormantperiodsufferingfromdroughtstress.
FIGURE3.BELOW‐AVERAGEPRECIPITATIONDURINGMAY(LEFT)ANDFROMJULYTHROUGHSEPTEMBER(RIGHT)IN2015.
FIGURE4.ABOVE‐AVERAGEPRECIPITATIONDURINGJUNEOF2015.
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BeginninginJulyof2015,theUMPDLbegantoreceivewhitepinesampleswithanuncharacteristic
symptom:blightedtipsoncurrentseason’sneedles.Symptomsofinfectionfromneedleblightfungi
typicallydeveloponolderneedleswhilethecurrentseason’sneedlesappeargreenandhealthy.The
conditionwasreportedfromWestVirginiatoMainebutaffectedtreeswerescatteredonthelandscapeand
inmanycasesweredirectlyadjacenttohealthytrees.Onamajorityofthesamples,anunknownfungal
pathogenwaspresentthatwaslateridentifiedasSeptorioidesstrobi.Whilethisspecieswasonlyrecently
describedithasbeenfoundtobeassociatedwithwhitepineneedleblightthroughoutnortheasternNorth
America(WykaandBroders2016,Wykaetal.2016).Mostoften,needletipswerestraw‐coloredtobrown
whilethebaseoftheneedleremainedgreenandhealthy.Needlelesions,sporemassesandcolorless,
asexualsporesareshownbelow(Figs.5&6).
FIGURE5:BLACK‐COLORED,CIRCULARLESIONSEXTRUDINGCLEARMASSESOFSPORESONBLIGHTEDNEEDLETIPS.
FIGURE6:ASEXUALSPORESPRODUCEDBYSeptorioidesstrobi.
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Asweenteredthelastmonthsofthe2015calendaryear,temperaturesthroughouttheregionwere
above‐average,especiallyinDecember(Fig.7).Thesewarm,lateseasontemperaturesmayhaveadversely
affectedtheabilityofwhitepinestoacclimateforcoldwintertemperatures.Droughtstressisalsoknown
toreducewinterhardiness.OncetemperaturesbecamemoreseasonableinJanuaryandFebruary,cold
injurymayhavebeeninflicted.However,theeffectofwarm,lateseasontemperaturesisspeculativeand
maynotbeacurrentfactorinwhitepinedecline.
FIGURE7:ABOVE‐AVERAGETEMPERATURESFROMOCTOBERTHROUGHDECEMBER(LEFT)THATWERE
PARTICULARLYPRONOUNCEDINTHEMONTHOFDECEMBERALONE(RIGHT).
Tosummarize,thecurrentdeclineofeasternwhitepineisnotfullyunderstoodandwilltakemanymore
monthstobetterunderstand.However,thefollowingfactorsshouldbeconsideredinthedecline:
1. Multipleneedleblightpathogensthatmayormaynotco‐occuronthesametree.
2. IncreasedprecipitationinthemonthsofMay,JuneandJulythatwouldpromoteneedleblight
infectionsondevelopingwhitepineneedles.
3. Environmentalstresssuchasdrought.
4. Branchcankering?CankeringbythefungalpathogenCaliciopsishasemergedasasignificantthreat
toforestwhitepines(seeMuncketal.2015)butmaynotbeasimportantinlandscapesettings.
LiteratureCited:
1.
2.
3.
4.
Brodersetal.,2015.Characterizationoffungalpathogensassociatedwithwhitepineneedledamage(WPND)
innortheasternNorthAmerica.Forests6:4088–4104.
Muncketal.,2015.ExtentandseverityofCaliciopsiscankerinNewEngland,USA:anemergingdiseaseof
easternwhitepine(PinusstrobusL.).Forests6:4360–4373.
WykaandBroders,2016.ThenewfamilySeptorioideaceae,withintheBotryosphaerialesandSeptorioides
strobiasanewspeciesassociatedwithneedledefoliationofPinusstrobusintheUnitedStates.FungalBiology
(Inpress).
Wykaetal.,2016.EmergenceofWhitePineNeedleDamage(WPND)inthenortheasternU.S.isassociated
withchangesinpathogenpressureinresponsetoclimatechange.GlobalChangeBiology(Inpress).
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