Loblolly Pine Health in the Southeastern U.S....Georgia; USDA Forest Service, Forest Health...

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LoblollyPineHealthintheSoutheasternU.S.KamalJ.K.Gandhi,DavidR.Coyle,BrittanyF.Barnes,KierD.Klepzig,LawrenceMorris,andJohnT.Nowak

ImportanceofSouthernPinesSouthernpinespeciessuchasloblolly,longleaf,shortleaf,andslashcovermuchofthesoutheasternU.S.,andareacriticalcomponentoftheregion’seconomy1.Loblollypineisthemostwidelyplantedspeciesinthesoutheasternregion,iscommerciallymanagedinplantationsandnaturalstands,andaccountsfornearlyhalfofthepinegrowingstock2.Thesepinestandsareecologicallyandeconomicallycriticaltotheregionastheyimprovesoilandwaterquality,createhabitatforvariouswildlifespecies,andprovidetimberandpulpwoodproductsworthtensofbillionsofdollarseachyearwithmanybenefitstolocalcommunities3,4.Asdemandsonourpineresourcesincrease,forestthreatssuchasurbanization,climatechange,andinvasionbynon-nativespeciesarealsoexpectedtoincrease1.Implementingspecificmanagementpracticescanminimizethesethreatsandassistmanagersandlandownerswithmaintainingthesustainabilityofpineforests.AbioticFactorsAffectingLoblollyPinesSoutheasternforestsarehistoricallymaintainedanddisturbedbyabioticandbioticfactors.Amongstabioticfactors,frequentunderstoryfiresareimportantinmaintainingandregeneratingpineforests,howeverfiresareusedlessfrequentlyinloblollypineplantations5.Inthelate19thandearly20thcenturies,manysoutheasternforestswereclearcutandharvested,thenconvertedintofarms,whichresultedinmajorsoilerosionissues(especiallyinthePiedmontregion)5(Fig.1A).Whenthesefarmlandswereabandonedinthe1930sand1940s,theynaturallyregeneratedtoforests,howevertheoriginalcover-typeandmanyassociatednativespecieswerelargelylostfromthesesystems1,5.Adverseweatherconditionssuchasdroughtandwind/ice-stormscanincreasepinesusceptibilitytoinsectsanddiseases6(Fig.1B).Thefrequency,duration,andunpredictabilityofdroughtandstormsareexpectedtoincreaseunderclimaticchangeswithensuingimpactstopinesustainability7.Forexample,catastrophicandseverefiresduetodroughtin2016-2017heavilyimpactedforestsespeciallyinGeorgia,NorthCarolina,andTennessee(Fig.1C).

Fig.1.Examplesofabioticfactorssuchas(A)soil-erosionafterfarming;(B)drought;and(C)severewildfiresthathavehistoricallyandarecurrentlynegativelyimpactingpineproductivity.

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BioticFactorsAffectingLoblollyPinesInsectPestsBioticagentssuchasbarkandwoodboringbeetlesaremajorfactorsaffectingpineplantationsandnaturalforests8,9.Thesebeetlescreatetunnelsunderthebarkandinwoodofthetree,thusgirdlingandkillingit.Anumberofbarkbeetlesarealsoassociatedwithpathogenicfungalspeciesthatfurthercontributetotreemortality.Southernpinebeetle(Dendroctonusfrontalis)isconsideredthemostdamaginginsectaffectingloblollypines10(Fig.2A).Southernpinebeetleoutbreakscankillhundredsofthousandsofpinetreeswithinaregioninagivenyear.Treestressanddamagethatresultfromdrought,poorsoilconditions,lightningstrikes,fungalinfectionsormechanicaldamageincreaseactivitiesofotherdamagingspeciesincludingpineengraverbeetles(Ips),blackturpentinebeetle(Dendroctonusterebrans),anddeodarweevil(Pissodesnemorensis)11(Fig.2B-C).Manywoodboringinsectssuchaspinesawyer(Monochamus),andotherlonghornandjewelbeetlesalsoshowincreasedactivityonstressed

trees,furthercontributingtodamageanddeath9(Fig.2D).Generalsignsandsymptomsofbarkandwoodboringbeetlesareroundorovalexit/entranceholes(<0.5inch)onthebark,sawdust(finetocoarse),pitchtubes,beetlegalleriesunderbark,branchdieback("flagging"),andgrowthreduction(Fig.3,Table1)11.

B

Fig.2.Examplesofeconomicallyimportantadultbarkandwoodboringbeetlespeciesinloblollypineplantations:(A)Dendroctonusfrontalis;(B)Ipsavulsus;(C)Pissodesnemorensis;and(D)Monochamusspecies(nottoscale).

A

C D

BFig.3.Examplesofsignsofbarkandwoodboringbeetleactivityonloblollypinetrees:(A)pitchtubesandboringdust;(B)Ipsbeetlegalleriesunderbark;(C)Dendroctonusfrontalisgalleriesunderbark;and(D)chipcocoonsofPissodesnemorensis.

A C D

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Species CommonSigns(Fig.3)BlackTurpentineBeetle

Large(quarter-sized)pitchtubesalongrootflareuptoabout5feet,reddishbrownboringdust,largerentrance/exitholes,J-shapedfeedinggalleriesunderthebark

DeodarWeevil ChipcocoonsunderthebarkIpsBeetles Smaller(dime-sized)pitchtubesthroughoutthebole,reddishbrownboringdust,

smallentrance/exitholes,H,YorX-shapedgalleriesunderthebarkSouthernPineBeetle Smaller(dime-sized)pitchtubesthroughoutthebole,reddishbrownboringdust,

smallentrance/exitholes,S-shapedgalleriesunderthebarkWoodborers Coarseorfinewhiteboringdustorchips,roundorD-shapedexitholesFungalPestsFungalpathogensarecommoninloblollypinestands,andtheiractivityvarieswithsoiltypesandland-usehistory.Inmoststands,activityoftheseorganismshasminimalimpactontreehealth;howeverundersomeconditionstheycanhavemajorimpacts.Heterobasidion(i.e.,Fomes/Annosus/Annosum)rootdisease(causedbyHeterobasidionirregulare)ismostactiveinstandswithwell-drained,coarse-texturedsurfacesoils(sandandsandyloamAhorizons)afterthinninginwintertimewhensporeproductionisthehighest12.Fungalsporesinfectstumpsandmoveintotreerootsandsurroundingtreesgenerallythroughrootcontactcausingtreedeath(Fig.4).Infectioncentersofdeadanddyingtreesoccuraroundinfectedstumpsthatcontinuetoexpandforupto10years.Stumptreatmentsorsummerthinning(below34°latitudeonly)cansignificantlyreduceinfection.

Littleleafdiseaseisamajorproblemonoldertrees(>40yearsold)growingonsoilsthathavehighsubsoilclaycontent,poorinternalsoildrainage(eithernaturallyorduetosoilcompaction),andlownutrientavailability,especiallyphosphoruslevels13.Phytophthoracinnamomiisthepathogenthatismostcommonlyassociatedwithlittleleafdisease14.Symptomsoflittleleafdiseaseincludeshorteningofneedles,abundantsterileconeproduction,androotdeath.Sincethisdiseaseaffectsoldertreesthatarenotveryresponsivetofertilizerorothertreatments,harvestingfollowedbysitepreparationthatincludessoiltillage(suchasa

Table1.Commonsignsofinsectsonstressed,dying,anddeadloblollypinetrees.

A B Fig.4.Heterobasidionrootdiseasewith(A)stringyrootsshowingsapstain;and(B)fruitingbodiesatthebaseofthetree.

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combinationplow),fertilization,andreplantingmaybetheonlyoptionavailabletothelandowner.LoblollyPineDiebackandMortalityDuringthelastseveraldecades,therehavebeenreportsofdiebackandmortalityofloblollypinesinthePiedmont,Sandhills,andUpperCoastalPlainphysiographicregions.Countiesinwest-centralGeorgiaandeast-centralAlabamaarereportedtohavethehighestlevelsoftreediebackanddeath.Thisphenomenonhasbeenreferredtoas"loblollypinedecline"or"southernpinedecline"(SPD)bysomeresearchersandforestmanagers,andsymptomsincludecrownthinning,yellowingofneedles,reductionsingrowth,androotandbranchdeath15.AnalysisofFIAdataandfieldvisitstositespreviouslycharacterizedashavingSPDhadavarietyofabiotic(e.g.,soiltypesandclimate)andbiotic(e.g.,insects,pathogens,andgenetics)factorsthatwerecausingindividualstandstoshowsymptomsofdecline16.FromthisresearchitappearsthatanumberofunrelatedproblemsarebeinglumpedunderthenameSPD,whichleadstomisdiagnosisofcausalfactorsofdamagedstands.Furthercontroversyhasalsoarisenduetothefocusofresearchoncommoncontributingfungiandinsects.SouthernLeptographiumfungiandtheirvectors(Hylastes,Hylurgops,andPachylobiusspecies)areubiquitousindamagedpinestands15,17.Therearemanyunknownsabouttheecologicalandeconomicimpactsofthesesouthernroot-feedingweevilsandLeptographiumspeciesinhealthyandstressedloblollypinestands.However,nonehaveproventobeprimarypathogens16,18.Recentstudiesshowroot-feedingweevilsmainlyattackstumpsandstressed/dyingtreesinsteadofhealthyones,whichsuggeststhatsilviculturalactivitiesthatoptimizetreehealthwillminimizetheiractivities18.MaintainingLoblollyPineHealthLoblollypinetreehealthcanbemaintainedbycorrectivetreatmentsatstandestablishmentcombinedwithappropriateintermediatestandtreatments.Sitepreparationtillagethatbreaksuprestrictivesubsoillayerscanimprovegrowthandtreevigorinmostsitesandmaybeparticularlyvaluableonsiteswherelittleleafdiseaseisexpectedtooccur19.Atestablishment,fertilizationwithphosphorusorphosphorusplusnitrogenshouldalsobeconsideredforthesesitesaswellasothersiteswheresoilstestsindicatelowphosphorusavailability20.Herbaceousweedcontrolduringthefirstgrowingseasonisgenerallyrecommendedandisalwaysrecommendedwhenfertilizationatestablishmentincludesnitrogen.Hardwoodcontrolmayormaynotbeneeded.Onsiteswithlowhardwoodcompetition(<1,800hardwoodrootstock/acre),herbaceousweedcontrolissufficient20.Post-planting,regularlow-intensityprescribeburningorherbicidetreatmentswillalsoreducehardwoodplantcompetition(Fig.5A).Iftreeswereplantedathighdensity,thenthinningisrecommendedto80-100ft2/ac(oftenthiswillbetimedtocoincidewithnitrogenandphosphorusfertilization)21(Fig.5B).Duringthinning,damagetotreeboleandrootsshouldbeavoidedotherwisepestproblemscanbeexacerbated.Selectionofqualitycontractorscoupledwithon-siteinspectionduringtheoperationandcontractualprovisionstoceaseoperationsduringwetweatherwillhelpminimizedamage.Healthyloblollystandsmayhaveafewdeadtrees,butwidespreaddiebackshouldnotbepresent.

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Contactanextensionagent,stateforestryagent,oraconsultingforesterforfurtherassistancewithpinetreehealthissuesandmanagementoptions.Alwaysusealicensedpesticideapplicatoranduselabeldirectionswhenapplyingpesticides.MoreinformationonpesticideapplicationisavailablefromtheUSDAForestService(http://www.fs.fed.us/foresthealth/pesticide/),orfromyourstate’scooperativeextensionservice.AcknowledgementsWearegratefulforthefundingprovidedbyD.B.WarnellSchoolofForestryandNaturalResources,UniversityofGeorgia;USDAForestService,ForestHealthProtection;andUSDAForestService,SouthernResearchStation.ValuablecommentswereprovidedbyChrisAsaroandMichelleCram(USDAForestService,ForestHealthProtection),andElizabethBentonandJayShelton(D.B.WarnellSchoolofForestryandNaturalResources,UniversityofGeorgia).Photocredits-AuburnUniversity;J.R.Baker&S.B.Bambara,NorthCarolinaStateUniversity;ChuckBargeron,UniversityofGeorgia;ChrisEvans,UniversityofIllinois;GeorgiaForestryCommission;LacyL.Hyche,AuburnUniversity;GeraldJ.Lenhard,LouisianaStateUniversity;PaulA.Mistretta,USDAForestService;MinnesotaDepartmentofNaturalResources;andErichG.Vallery,USDAForestService-SRS-4552,allatBugwood.org,andKamalJ.K.Gandhi,UniversityofGeorgia.

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Authors:KamalJ.K.GandhiisanAssociateProfessorattheD.B.WarnellSchoolofForestryandNaturalResources,UniversityofGeorgia,Athens,Georgia.DavidR.CoyleisanExtensionSpecialistattheSouthernExtensionRegionalForestry,Athens,Georgia.BrittanyF.BarnesisaResearchProfessionalattheD.B.WarnellSchoolofForestryandNaturalResources,UniversityofGeorgia,Athens,Georgia.KierD.KlepzigisDirectoroftheJosephW.JonesEcologicalResearchCenter,Newton,Georgia.LawrenceMorrisisaProfessorattheD.B.WarnellSchoolofForestryandNaturalResources,UniversityofGeorgia,Athens,Georgia.JohnT.NowakisaForestEntomologistwiththeUSDAForestService,ForestHealthProtection,Asheville,NorthCarolina.

PublicationWSFNR-17-39 August2017

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