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457chAPTeR 16. Invasive Pests—Insects and Diseases
DonaldA.DuerrandPaulA.Mistretta1
key FiNDiNGS
•NonnativepestspecieshaveincreasingimpactsintheSouthregardlessofclimatechange,patternsoflandownership,orchangesinthecompositionofvegetation.
• “New”nonnativeinvasiveinsectsanddiseaseswillhaveseriousimpactsonsouthernforestsoverthenext50years.Somespeciessuchasemeraldashborer,laurelwilt,andthousandcankersdiseaseareexpandingrapidly;theythreatentheecologicalviabilityoftheirhoststhroughoutlargeareasoftheSouth.
•Giventhetrendinintroductionsofnonnativeinsectpestsandplantpathogensoverthelast100years,wecanexpectadditionalintroductionsofpreviouslyundocumentedpests(insects,fungalpathogens,plantparasiticnematodes,etc.)fromforeigncountriesthatwillhaveseriousconsequencesforsomenativeforestplantspecies.
•Whenhostmaterialforagiveninsectordiseaseisprojectedtoincreaseoverthenext50yearsasaresultofclimatechangeormanagementchoice,wecanexpectmorepestactivity;forexample,morepineacreageenablesmoresouthernpinebeetledamage.Conversely,ifhostmaterialdecreases,theoverallimpactofpestsutilizingthathostmaterialwilllikelydecrease.
•Veryfewindisputableprojectionscanbemadeabouttheeffectsofclimatechangeonnativeornaturalizedpests.Althoughclimate-change-inducedhostabundanceisexpectedtoincreasetheactivityofsomepests,others(suchasgypsymoth)maybecomelessactivewithwarmertemperaturesdespiterelativelysimilarlevelsofhostavailability.
•Thescientificliteratureandthebodyofexpertopinionareinconclusiveinpredictingtheeffectsofclimatechangeonmanypests’activitylevels,oftenevenlackinghistorictrenddata.However,basedonanecdotalreportsfromprofessionals,andintheabsenceofotherdata,wegenerallyassumethatpestactivitylevelsoverthenext50yearswillbesimilartothepast50yearswithrespecttoimpactonpreferredhosts.
1DonaldA.DuerristheStaffEntomologistandPaulA.MistrettaisaStaffPathologistandRegionalPesticideSpecialist,SouthernRegion,U.S.DepartmentofAgricultureForestService,Atlanta,GA30309.
•Asignificantsourceofuncertaintyinprojectingpestimpactsistheadequacyofpreventionandsuppressionmethods:howeffectiveareexistingmethods,comparedwiththosethatmightbeavailableinthefuture;howwillingandablearelandmanagersorlandownerstoadoptmanagement/controlmethods;howmuchfundingisavailablecomparedtotheamountneededforimplementation.
•Undertheinfluenceofclimatewarminghostplants,pestsandpestcomplexesareexpectedtomigratenorthwardandtohigherelevations.Becausemigrationratesdifferamongtheaffectedspecies,migratingplantsareexpectedtoformnewassociations,whichwillthenaffectthepests,theirhostpopulations,andtheinteractionsamongthem.Unexpectedpestsverylikelywillbecomeimportant,whilesomethatarecurrentlyactivewillbelesssevereintheirnewhabitats.Ashostplants“migrate”tothenorthanincreaseintheincidenceofdeclinesyndromeofplantsintheirpreviousrangeisexpected.
•Althoughnotexpectedtobeasignificantprobleminthenext50years,themigrationoflowerelevationplantstohigherelevationscouldultimatelyeliminateoratleastseverelyrestrictthehostrangesofcurrenthighelevationplantassociations.Peststhatactonarestrictedhostbase,suchasthebalsamwoollyadelgidandbutternutcanker,couldbecomefarmoresignificantecologicallyinareasofrelicthostpopulations.
•Climatechangewillleadtoextrauncertaintyindecisionmaking,especiallyinareaswherethechangescauseincreasedvariabilityinlocal(fragmented)climateregimesthatexceedhistoricalvariabilityoflocalweatherpatterns.
iNTRoDucTioN
Animportantpartofthesouthernforestedlandscapeisthearrayofinsectanddiseasepeststhatsignificantlyaffectthemanagementofforestresourcesonarelativelybroadscale.Thelistof21keypeststhatweredocumentedlessthanadecadeago(WardandMistretta2002)hasalreadyexpandedto30.
Thegoalofthischapteristoprojectthebehaviorofinsectanddiseasepeststhatweanticipatewillaffectforestresourcesoverthenext50years,basedonchangingclimate,
Chapter 16. invasive Pests—insects and Diseases
458The Southern Forest Futures Project
humanactivity,andbiologicfactors.Ourprimaryfocusisonclimatechangeanditssub-elementsoftemperaturerégime(dominatedbytemperatureextremes),overallpatternofsolarradiation,andrainfallpattern.Allavailableclimatechangescenariospredictanenvironmentinwhichweexpectvegetationchangestooccur(Iversonandothers1999).Concurrentwithecologicalchangeswillbeashiftinthepeststhatfunctionwithinanalteredvegetativelandscapeunderchangedtemperature,rainfall,andotherclimaticconditions.Theimpactsonpestactivity,inturn,mayinfluencethedirectionorscopeofotherchangesinforesttypeandstructure.
Thefocusofthischapteristhe30speciesofpestinsectsorfungalpathogensthatcausediseasesprojectedtobeoffutureconcern,withemphasisonthefollowingkeyissues:
•Thehistoricalandforecastedfuturespreadofhighthreatinsectsanddiseases
•Otherpestsinvadingsouthernforestsandotherhighthreatspeciespoisedtoentertheregion
•Expectedconsequencesofthespreadofhigh-threatpestspeciesforforestproductivity,ecosystemcompositionandbiodiversity,threatenedandendangeredspeciesandtheirhabitats,watershedandsoilhealth,carbonstorage,andfiredynamics
• Potentialseverityofpestspeciesthreatsrelativetootherthreatsandtofutureforestsustainability
•Forestspeciesorpopulationsthatarelikelytobelostordramaticallydegradedbypests;theresultingchangesinthecompositionofsouthernforestsoverthenext50years;andthedegreeofcertaintyintheseoutcomes
•Adaptivestrategiesandmethodsforinvasivepestmanagementthatcouldmitigatetheeffectsofpredictedfutureoutbreaks
meThoDS
Inresponsetotheissuesdevelopedabove,wepresentabriefextractofrelevantinformationaboutthepeststhatarewellestablishedinsouthernforests(WardandMistretta2002);weaddmoredetaileddescriptionsofseveralnewpestsorpestcomplexesthathaveemergedinthepastfewyears;weapplytheresultsofpastresearchonpestsandpestmanagementtoexpectedchangesinsouthernforestsoverthenext50years;weidentifymanagementstrategiesforrespondingtopestsinachangingenvironment;andweidentifyresearchneededtoimproveourknowledgeaboutpestswiththeirhostsandtheirinteractionswiththeirchangingenvironment,therebyenablingamorequantitativeapproachtoforecastinginthefuture.
DATA SouRceS
Informationforthischapterisderivedfromtwoprimarysources,selecteditemsfromtheextensivebodyofpublishedscientificliterature,andtheexperienceoftheauthorsandtheircolleaguesinStateandFederalagencies,universities,andotherpublicorprivateorganizationsthatareengagedeitherinresearchorfield-basedpestmanagementactivities.AdditionalinformationaboutforestpestsandtheircontrolisreadilyavailablefromStateandFederalforestryagenciesorontheInternet(twogoodstartingpointsarehttp://fhpr8.srs.fs.fed.us/andhttp://www.na.fs.fed.us/spfo/pubs/fth_pub_pages/fidl.htm).Also,appendixCcontainsadditionalresources(References)notcitedherebutwhichprovidevaluableadditionalbackgroundforunderstandingthebiologyandecologyofthepestsdiscussed.
ReSulTS
ThescientificliteratureonclimatechangeandotherenvironmentalconsiderationsissummarizedinappendixC,whichalsoprovidesthebackgroundinformationonourapproachtopestmodelingandfutureprojectionofimpacts.BelowweaddressthepestsprojectedtoinfluencetheforestsoftheSouthoverthenext50years,theirpotentialdamage,potentiallyeffectivemanagementstrategies,andresearchneededtobetterunderstandandmanagethem(table16.1).
Ofthe30forestpestsintheSouthdiscussedbelow,21arewellestablishedand9arerelativenewcomers.Pestsareroughlyevenlydividedbetweenthoseaffectingsoftwoodsandthoseaffectinghardwoods.
insect Pests of Softwoods
Balsam woolly adelgid—Impactsofbalsamwoollyadelgid,Adelgespiceae,werefirstdocumentedin1957onFraserfirintheSouthernAppalachians.Thefivemajorareasofhigh-elevation,spruce-firforestinNorthCarolina,Tennessee,andVirginiaarehighlyvaluedfortheirscenicandrecreationvalues,attractingseveralmillionvisitorsannually(WardandMistretta2002).Inaddition,severalspeciesoffloraandfaunarelyonmaturespruce-firhabitatforsurvival,andmanyarefoundonlyinthisenvironment.ThebalsamwoollyadelgidhasinfestedFraserfirinallfiveareas.Damagecausedbytheadelgidhasdegradedsceneryandrecreationvalueandputthishabitatofdependanttreespeciesatgreatrisk.
459chAPTeR 16. Invasive Pests—Insects and Diseases
Table 16.1—Important insect and disease pests of southern forests
Pest Pest’s scientific name
Type of pests / abiotic factors origin
Forest type or species affected
Annosum root disease Heterobasidion annosum Fungus Native Pines in the loblolly-shortleaf and longleaf–slash forest types
Asian longhorned beetle Anoplophora glabripennis Insect China Most hardwoods, but especially maples.
Baldcypress leafroller Archips goyerana Insect Native Baldcypress in oak-gum-cypress forest type
Balsam woolly adelgid Adelges piceae Insect Europe Fraser fir in the spruce-fir forest type
Bark beetles (other than southern pine beetle)
Ips avulsus, I. calligraphus, I. grandicolli, & Dendructonus terebrans
Insect Native Pine in the loblolly-shortleaf and longleaf–slash forest types
Beech bark disease Nectria coccinea var. faginata, N. galligena (fungi); 2 (at least) insect vectors
Complex of insects and fungi
Unknown American beech in the oak-hickory forest type
Brown spot needle disease
Scirrhia acicola Fungus Native Longleaf pine in the longleaf–slash forest type
Butternut canker Sirococcus clavigignenti-juglandacearam
Fungus Unknown Butternut in the oak-hickory forest type
Chestnut blight Cryphonectria parasitica Fungus Asia American chestnut, chinquapins, several species of oak in the oak-hickory forest type
Dogwood anthracnose Discula destructiva Fungus Unknown Dogwood in the oak-hickory forest type
Dutch elm disease Ophiostoma ulmi (formerly called Ceratocystis ulmi) & Ophiostoma novo-ulmi (fungi); two bark beetles
Complex of fungi and insects
Europe All elm species
Emerald ash borer Agrilus planipennis Insect Asia All ash species
Forest tent caterpillar Malacosoma disstria Insect Native Hardwoods in the oak-gum-cypress forest type
Fusiform rust Cronartium fusiforme f. sp. fusiforme
Fungus Native Loblolly and slash pines in the loblolly-shortleaf and longleaf slash types
Gypsy moth Lymantria dispar Insect Europe and Asia
Hardwoods (all types)
(Continued)
460The Southern Forest Futures Project
Table 16.1—(continued) Important insect and disease pests of southern forests
Pest Pest’s scientific name
Type of pests / abiotic factors origin
Forest type or species affected
Hardwood borers Various Insect Native All species of hardwoods
Hemlock woolly adelgid Adelges tsugae Insect Asia Hemlocks
Laurel wilt Raffiella lauricola (fungus), Xyleborus glabratus (insect)
Complex of an insect and fungus
Asia Lauraceae, especially Redbay
Littleleaf disease Phytophthora cinnamomi, Pythium sp.
Tree decline complex; fungi and site factors
Southeast Asia (likely)
Shortleaf and loblolly pines in the loblolly-shortleaf forest type
Loblolly pine decline As a minimum: various fungi (Lophodermium spp.) and insects (Hylastes spp.)
Tree decline complex; insect and fungi
Unknown Pines
Nantucket pine tip moth Rhyacionia frustrana Insect Native Pines
Oak decline Armillaria sp., and other secondary fungi
Tree decline complex; site conditions and fungi
Mixed Oaks
Oak wilt Ceratocystis fagacearum Fungus Native Oaks in the oak-hickory forest type
Pine reproduction weevils Hylobius pales, Pachylobius picivorus
Insect Native Pines
Sirex woodwasp Sirex noctilio (insect), Amylostereum areolatum (fungus)
Complex of an insect and fungus
Europe, Asia, northern Africa
Pines
Soapberry borer Agrilus prionurus Insect Mexico Western soapberry
Southern pine beetle Dendroctonus frontalis Insect Native Pines
Sudden oak death Phytophthora ramorum Fungus Unknown Oaks
Texas leafcutting ant Atta texana Insect Central and South America
Pine (reproduction)
Thousand cankers disease
Geosmithia sp. (fungus), Pityophthorus juglandis (insect)
Complex of an insect and fungus
Unknown Black walnut
462The Southern Forest Futures Project
hemlocktoserveascoverandnestinghabitatforbirdsandsmallmammals.
Giventheadelgid’scurrentrateofspread,itcouldinfestnearlytheentiresouthernrangeofeasternhemlockandCarolinahemlockwithinthenext50years.Someisolatedareaswithintheinfestedrangeandsomeareasofhemlocksthatareseparatedfromthemainrange(innorthwesternAlabama,forexample)mayescapeinfestation.Inalllikelihood,withinthenext50yearshemlockwoollyadelgidwillkillmostofthehemlocksthatarealivetodayintheSouth.ThelossofhemlockwillbeoneofthemajorimpactscausedbynonnativeinvasivespeciestoSouthernforestsinthenext50years.
Anumberofsuppressiontacticsshowsomepromiseforpreventingthelossofsignificantnumbersofhemlocksoverthenext50years.Treatmentoftreeswithimidacloprideffectivelycontrolshemlockwoollyadelgidsforseveralyears(Cowlesandothers2006).Distributionoftheinsecticideintotreecrownsismoreeffectivewithsoildrenchorinjectionthanwithsteminjection(Dillingandothers2010).Dinotefuranisalsobeingusedwithsuccess.Currentinsecticidetreatmentsareappliedtoindividualtreesandfunctionprimarilyasatemporaryprotectionmeasureforarelativelysmallnumberoftrees.Atthistime,insecticideapplicationoverlargeareasisneitherlogisticallyfeasiblenorcost-effective.Severalbiologicalcontrolagents(beetlepredators)havebeenandarebeingreleased,andsomearesuccessfullyestablishing(Mauselandothers2010).Moretimeislikelyneededbeforeconclusiveimpactsofbiologicalcontrolagentsonthehealthofhemlockforestscanbeshown.Establishmentofacomplexofnaturalenemiesinagivenareaisdesiredtoachievelong-termsuccess.InJune2009,researchersandforesthealthprofessionalsbeganevaluatingtheefficacyofLecanicilliummuscarium,aninsect-killingfungusthatisregisteredasabio-pesticideinEurope(Grassano2008).
Researchandworkisbeingdoneonhemlockhostresistanceandex-situconservationofhemlockseedlingsandgeneticdiversity(Bentzandothers2002,Jettonandothers2008,Jettonandothers2010,Montgomeryandothers2009,Poolerandothers2002).Theseeffortsmayallowscientistsandlandmanagerstoreintroduceadelgid-resistanthemlocksinthefuture.
Climatechangeisunlikelytoreversethespreadofhemlockwoollyadelgids.Inthenorthernpartofthehemlockwoollyadelgidrange,lowminimumwintertemperaturescansignificantlyknockbackpopulationsandappeartolimitspread.Therefore,wecanassumethatclimatewarmingwouldlikelypromoteanorthwardexpansionoftheadelgid(Paradisandothers2008).Thesouthernrangeofhemlockiscurrentlynotbenefittingfrommuchcoldwinter
knockback—awarmingclimatewouldpresumablyonlyexacerbatethesituation.
Nantucket pine tip moth—TheNantucketpinetipmoth,Rhyacioniafrustrana,isoneofthemostcommonforestinsectsintheSouth(Berisford1988).Althoughitisusuallyconsideredasouthernpest,itsrangeincludesmostoftheeasternhalfoftheUnitedStates.
MostcommercialpinespeciesaresusceptibletoattackbytheNantucketpinetipmoth,butthereareconsiderabledifferencesinrelativesusceptibility.Amongthesouthernpines,longleafnurseryseedlingsandallagesofshortleaf,loblolly,andVirginiapinesarehighlysusceptible,whileslashandolderlongleafpinesarehighlyresistant.
Damageisnormallytransitoryornegligibleinforeststandsbutcanbesevereforseedlingsandsaplingsyoungerthan5years,resultingindeformitiesandlossofgrowth.
Basedonthewarmerandpossiblydrierclimatethatisexpectedoverthenext50years,theactivityanddamagelevelsofNantucketpinetipmotharelikelytoincreaseintheSouthandextendtonorthernareas(Midwest,NewEngland)wheretipmothhasnotbeenmuchofamanagementconcern.Activitymayincreaseandcontinueintothewintermonths,ascouldthenumberofgenerationsperyear.Nantucketpinetipmothsareprimarilyaprobleminyoungloblollymonocultures.Totheextentthatlandmanagersincreasetheplantingofloblollymonoculturesinthenext50years,damagefromtheNantucketpinetipmothislikelytoincrease.
Anumberofeffective,chemicalcontroloptionsexistforthispest(Asaroandothers2003).Ifpopulationlevelsaremonitoredinatimelyandregularfashion,andarefollowedupbyappropriateinsecticideapplications,tipmothdamagecanbeminimized.Chemicalcontroloptionsareeffective,especiallythenewsystemicinsecticides.However,theyareoftenprohibitivelyexpensiveandwillprobablynotbeadoptedundermostcommonlyacceptedclimatescenariosunlesstipmothpopulationpressurebecomesquitehigh.
Other bark beetles—Althoughthesouthernpinebeetleisthemostdamaginginsectinsouthernpineforests,itisonlyoneoffivepinebark-beetlespeciesofconcernforforestmanagersintheSouth.Theothersarethesix-spinedengraver,Ipscalligraphus,thesouthernpineengraver,Ipsgrandicollis,thesmallsouthernpineengraver,Ipsavulsus,andtheblackturpentinebeetle,Dendructonusterebrans.Thesebeetlesareusuallyconsideredsecondarypestsbecausetheynormallyinfestonlystressed,weakened,damaged,ordownedpines.Theyalsocolonizepinesthathavebeenattackedbysouthernpinebeetlesoranotherbarkbeetlespecies.HostspeciesintheSouthincludeloblolly,shortleaf,Virginia,longleaf,easternwhite,pitch,slash(P.
463chAPTeR 16. Invasive Pests—Insects and Diseases
elliotii),andsand(P.clausa)pines.Bothpurepineandoak-pinestandsmaybeaffected(ConnerandWilkinson1983,SmithandLee1972,USDAForestService1985a).
Attacksbyblackturpentinebeetlesmaycontinueforseveralmonthsbutinfestationisnotalwaysfatal.Multipleattacksaroundtheentirecircumferenceofthetreearerequiredtocausemortality(SmithandLee1972,Staebenandothers2010,USDAForestService1985a).
Thesmallsouthernpineengraverandthesix-spinedengraverarethemostaggressiveandmaykillsmallgroupsoftrees.Lossesmaybeextensiveduringperiodsofdrought(ConnerandWilkinson1983,USDAForestService1985a).
Thesecondarybarkbeetlesplayavitalroleinshapingforeststructureandmayhaveagreaterimpactonregulatingpinestandsthansouthernpinebeetles(Paineandothers1981,Thatcher1960a).Theyattackweakenedorseverelystressedtreesandthosereachingsenescence.Largeinfestationsdeveloponlyoccasionally,usuallyafterwidespreadenvironmentalstress,suchasthatcausedbydrought,stormdamage,orwildfire.Theiractionservestothinthepineforests,reducingcompetition,leavingthestrongertrees,anddecreasingtheriskofsouthernpinebeetle(SPB)outbreaks.
Theimpactofthesebeetlesdependslargelyonmanagementactivities(Coulsonandothers1986).Engraversalsobreedindownedmaterial,soitisdifficulttosubstantiallyreducepopulations,butpreventionmethods(suchasloweringplantingdensities,thinningstands,andcuttingandremovinggroupsofinfestedtrees)canreducedamage.
Inunmanagedstands,theyattacksingletreesorsmallgroupsofpinesandreducepinebasalarea.Theyprovideopeningsforpinereproductionorforestablishedhardwoodstogrow.Theeffectsareoftennotnoticeableexceptduringperiodsofextendeddrought,afterstormdamage,orattheendofSPBepidemics.
Increasedtemperatureanddecreasedprecipitationwouldstresspinesandcouldthereforeincreasetheimpactsofthesebarkbeetles,butitisunlikelythattheywillbecomeprimarypeststhatkilllargeareasoftrees.Thesefourbarkbeetlespeciesmaymovenorthwardaswintersbecomewarmer.
Pine reproduction weevils—Palesweevil(Hylobiuspales)andpitch-eatingweevil(Pachylobiuspicivorus)aretwoofthemostdamaginginsectpestsofpineseedlingsintheSoutheasternUnitedStates.Insouthernforests,theyarefoundwhereverpineoccurs.Adultweevilsofbothspeciesareattractedtonewlyharvestedsites,wheretheybreedinloggingslash,stumps,andoldrootsystems;theycauseeconomiclossesbyfeedingonthebarkandoftenkillingplantedseedlings.Ifseedlingsareplantedonoradjacentto
siteswithfreshstumpsordamagedtrees,itiscommontohave30to60percentweevil-causedmortalityamongfirst-yearseedlings,withinstancesof90percentormoremortalityrecorded(Thatcher1960b).Athirdspecies,theeasternpineweevil(Pissodesnemorensis),isgenerallylesscommonbutisknowntokillterminalandlateralbranchesandgirdlethestemsofsmalltrees(Doggettandothers1977,Nordandothers1984).Thereproductionweevilsarealmostneveraprobleminforestmanagementunlessseedlingshavebeenplantedonoradjacenttositeswithfreshstumpsordamagedtrees.Forestersusuallyavoidthisproblemoncutoversitesbydelayingplantingorbyplantingtreatedseedlings.
Palesandpitch-eatingweevilspreferloblolly,shortleaf,pitch,andeasternwhitepines.Theyalmostneverattacklongleafandslashpines,butonrareoccasionshavebeenobservedfeedingonhardwoods.Althoughtheeasternpineweevilpreferscedar,italsoattacksmostsouthernyellowpines,suchasloblolly,slash,andshortleaf.Palesandeasternpineweevilsmayserveasvectorsforvariouspathogenicfungi.
Thefutureoutlookfortheactivityanddamagelevelsofreproductionweevilsissimilartotherecentpast.AwarmerclimatemayallowtheseinsectstoextendtheirrangesnorthintoCanada.Warmersouthernwintermonthsmayallowthemtoincreaseand/orprolongactivityandtoproducemoregenerationsperyear.Decreasedprecipitationmayreducetheiractivity.Theimpactsofthesepestsaremoredependentonstandmanagement(andwhetherseedlingsweretreatedwithinsecticides)thanonclimaticconditions.Ifpinesareplantedandthenleftunmanagedoverthenext50years,wecanexpectincreaseddamagefrompinereproductionweevils.
Sirex woodwasp—Sirexwoodwasp,Sirexnoctilio,isnativetoEurope,AsiaandnorthernAfricaandhasbeenintroducedtoNorthAmerica,SouthAmerica,NewZealand,Australia,andSouthAfrica.InAustralia,SouthAfrica,andSouthAmerica,itisconsideredanimportantpest,causingsignificantmortality(Oliveiraandothers1998)instandsplantedwithNorthAmericanpines,especiallyMontereypine(P.radiata)andloblollypine.HaugenandHoebeke(2005)reportthatotherknownsusceptiblepinesincludeslash,shortleaf,ponderosa(P.ponderosa),lodgepole(P.contorta),andjack(P.banksiana).
Femalescanproduceupto450eggsanddepositthem(mostlysingly)belowthesurfaceofthebarkclosetothecambium.Thefemalealsodepositsmucusandabasidiomycetesymbioticfungus,Amylostereumareolatum,whichgrowsrapidlyandexcreteswood-digestingenzymes.Whenthelarvaehatchtheyboreintothewood,butfeedonwoodalreadycolonizedbythefungus.Thefungusandmucusacttogethertokillthetreeandcreateanenvironmentsuitableforthedevelopmentofthelarvae.
464The Southern Forest Futures Project
SirexwoodwasphasnotcausedwidespreadmortalityintheNorthAmericanareaswhereitisestablished,norhaveanypopulationsbeenreportedintheSouth.Howeverwithinthenext50years,itisverylikelythatnaturalorhuman-aidedspreadwillintroducethispesttosouthernforests.ManyoftheSouth’smostimportantpinespeciesaresusceptibletoSirexandmanytreeswillsuccumbifattacksareasaggressiveastheyareinSouthAmericaandAustralia.Althoughthisscenariocouldresultincatastrophicecologicalandeconomiclosses,thecomplexityofsouthernforests(mixedstands,highbiodiversity,manypossiblecompetitors,predatorsandparasitoids)contrastswiththemonoculturepineplantationsinothercountrieswherethepesthasbeenmostdamaging.Manystudiesareunderwaytoassessthepotentiallevelofdangertosouthernforests.AnationalriskmapforSirexhasbeendeveloped(seehttp://www.fs.fed.us/foresthealth/technology/invasives_sirexnoctilio_riskmaps.shtml)andriskmapsspecifictotheSouthareindevelopment.
IftheSirexwoodwaspbecomesestablishedintheSouthandactsasaprimary“treekiller,”effectivepreventionandsuppressiontechniquesareavailable,includingthecurrentpracticeofthinningstandstoincreasegrowthandvigorandreducesusceptibilitytobarkbeetles.Inothercountries,Sirexwoodwasphasbeensuccessfullymanagedusingbiologicalcontrolagents.Thekeyagentisaparasiticnematode,Deladenussiricidicola,whichinfestsSirexwoodwasplarvae,andultimatelysterilizestheadultfemales.Infestedadultfemaleslayinfertileeggsthatarefilledwithnematodes,whichfurtherspreadsthenematodepopulation.Thenematodescaneffectivelyregulatethewoodwasppopulationbelowdamaginglevels.AsSirexwoodwaspestablishesinnewareas,thisnematodecanbeeasilymass-rearedinthelaboratoryandintroducedbyinoculatingitintoinfestedtrees.BiologicalcontrolemployingthesenematodesisbeingevaluatedforuseinU.S.forests.Ifeffective,itshouldprovideagoodcontroloptionforsouthernlandownersandlandmanagers.
Theeffectsofchangesintemperature,carbondioxide,andprecipitationonSirexwoodwaspactivityandaggressivenessareunknown.IfpineacreageincreasesthroughouttheSouthorincertainareasoftheSouth,susceptibilityoftheseareastoattackwillincrease.
Southern pine beetle—Southernpinebeetle(SPB),Dendroctonusfrontalis,isthemostdestructiveinsectpestofpineforestsintheSouth(ThatcherandConner1985).Populationsbuildrapidlyduringperiodicoutbreaksandkilllargenumbersoftrees.Forexample,duringtheoutbreakof1999to2002,SPBkilledmorethanamillionacresofpinesvaluedatgreaterthan$1.5billion.However,duringperiodsoflowactivity,SPBpopulationsmaybesolowthat
itisdifficulttolocateasingleinfestedtree(ThatcherandBarry1982,Thatcherandothers1980)orcapturebeetlesinpheromonetraps(BillingsandUpton2010).
TheSPB,whichattacksallspeciesofpines,prefersloblolly(Pinustaeda),shortleaf(P.echinata),Virginia(P.virginiana),slash(P.elliottii)pond(P.serotina),andpitch(P.rigida)pinesbutseldomattackslongleafpine(P.palustris).SPBhasbeenobservedtosuccessfullyinfesteasternwhite(P.strobus)andTableMountain(P.pungens)pines.Maturetreesinpure,densestandshavelongbeenconsideredmostsusceptibletoSPBattack,butinrecentyearsunthinnedpineplantationshaveincreasinglysupportedSPBinfestations(CameronandBillings1988).Attacksarerarefortreesyoungerthan5yearsorsmallerthan2inchesindiameteratbreastheight(d.b.h.).
Duringoutbreaks,SPBactivitypeaksinearlysummerinStatesontheGulfofMexicoandinlatesummerandearlyautumnfarthernorth.
Inthelastfivedecades,largeacreagesofpineplantationshavebeenestablishedintheSouth.Even-aged,single-speciesplantationsbecomeincreasinglysusceptibletoSPBinfestationsastheyage.MillionsofacresofpineacrosstheSouthareathighhazardforSPBattackasshownbyregionalandStatemaps(Nowak[N.d.]).SPBhazardmapsandinformationabouttheirdevelopmentcanbeviewedat:http://www.fs.fed.us/foresthealth/technology/nidrm_spb.shtml.
SPBimpactsoverthenext50yearsareexpectedtobesignificant,especiallyifthepineacreageincreasesintheSouth,high-susceptibilityspeciesareplantedindenseplantations,andtheplantationsareleftunthinned.Awarmer,drierclimateislikelytoincreaseSPBactivityandimpacts.WarmertemperatureswilllikelyallowanincreaseinthenumberofSPBgenerationsperyearaswellastheportionoftheyearthatthebeetlesareactive.ThenorthernedgesofthesouthernregionandpinestandsthatarefarthernorththanthehistoricalSPBrange(suchasintheLakeStates,NewEngland,andCanada)arealmostcertaintoexperienceSPBactivityandimpactsthatareunprecedentedoratleastsignificantlygreaterthaninthepast.
ThereissomeuncertaintyanddebateaboutthepotentialeffectsofawarmerclimateonSPB(Tranandothers2007),andgeneralpredictionsaredifficulttomake.Anincreaseintemperature(particularlywarmerwinters)wouldallowmoregenerationsperyear.Gan(2004)andRiveraRojasandothers(2010)predictoutbreakstobecomemorefrequentasclimatechanges,althoughlackoflandscape-scaledataonhostabundanceanddistributionmayhaveledGantooverestimatefutureSPBactivity.Veryhighsummertemperaturesmayincreasebroodmortality,reducespotgrowthrates,andhinderpredation.Warmerwintertemperaturesmaydisrupt
465chAPTeR 16. Invasive Pests—Insects and Diseases
synchronizationofthelifecyclesrequiredforconcentratedspringemergencethatfavorsinitiationoflarge,newinfestations(BillingsandKibbe1978).
Theimpactofoutbreaksinthe1980swasmagnifiedbyanabundanceofcontiguousmaturestandsofsawtimber,manyofwhichhavebeenreplacedwithyoungplantations,atleastonnon-Federallands.Ifincreasedforestfragmentation,ayoungerageclassdistribution,andmorethinningofplantationsoccurinthenext50years,SPBimpactscouldbelowerinthefuture,despiteincreasesintemperatures.AndalthoughitisgenerallyacceptedthatincreasedtemperatureswillincreaseSPBactivityanddamage,otherfactors(forexampleforestcomposition,forestmanagement,directsuppression,etc.)maybemoremeaningfulindeterminingfutureSPBactivityanddamage(Friedenbergandothers2008).
Similartotemperature’seffectonSPB,thepotentialofmoistureregimetoincreaseordecreaseSPBproblemsisopentoconjectureandnotfullyunderstood.SomeexpertsbelievethatdroughtisamajorenhancerofSPBoutbreaks,whereasotherspointtotoomuchmoistureasaprimaryfacilitatingfactor.Ifthefrequencyofprecipitationextremes(yearsofextremewetnessordyness)increasesthroughouttheSouthoverthenext50years,itisprobablethatpineswillbecomestressedandincreasedSPBactivityanddamagewillresult.
Inadditiontotheeffectsthatforestcomposition,temperature,andmoisturewillhaveontheSPBoutlook,forestmanagementwillplayadefiningrole.Plantingtheproperspeciesforagivensite,lowerplantingdensities,andthinningofpinestandscanincreasestandvigorandresiliencyandpossiblyreduceSPBdamage.Whenoutbreaksdooccur,damagecanbeminimizedbyearlydetectionandmonitoringofspots,followedbypromptdirectsuppressionofactivespots(Billings1980).
Texas leafcutting ant—TheTexasleafcuttingant,Attatexana,targetsfirst-andsecond-yearpineplantationsineasternTexasandwestcentralLouisiana.Inlocalareaswheretheantsareabundant,itisnearlyimpossibletoestablishpineplantationsunlesstheantcoloniesareeliminated.TheannuallossofpineseedlingstoTexasleafcuttingantsisnearly12,000acres(Cherret1986,TexasForestService1982).
Awarmerclimatemayleadtoanincreaseand/orcontinuationofleafcuttingantactivityduringwintermonths.Decreasedprecipitationwouldlikelyhavetheoppositeeffect.Becausethisanthasastrongpreferenceforwell-drained,deepsandysoils(Moser1984,Vilela1986),climate-inducedspreadbeyonditscurrentdistributionisunlikely.Althoughleafcuttingantsarelimitedbyaveragelowtemperatures(warmertemperatureswouldlessenthislimitingfactor),their
spreadintonew,northernareasisgoingtobelimitedduetothelackofpreferredsoilsfortheant.ThereisapossibilitythatawarmerclimatewouldallownorthwardmovementintoareasofOklahomaandArkansasthathavedeep,sandysoils.Anewfipronilcontrolproduct,PTM™wasregisteredin2009,andaninsecticidalbaitisonthehorizon.RegularandconsistentapplicationoftheseproductshasthepotentialtoreducetheimpactsofTexasleafcuttingantsfromhistoricallevels.
insect Pests of hardwoods
Asian longhorned beetle—Asianlonghornedbeetle,Anoplophoraglabripennis,wasdiscoveredattackinghardwoodtreesintheUnitedStatesinthemid-1990s.Tunnelingbybeetlelarvaegirdlestreestemsandbranches.Repeatedattacksleadtodiebackofthetreecrownand,eventually,deathofthetree.ThebeetleprobablytravelledtotheUnitedStatesinsidesolidwoodpackingmaterialfromChina.ThispestbeetlehasbeeninterceptedatportsandfoundinwarehousesthroughouttheUnitedStatesandiscurrentlyinfestingtreesinNewYorkCity,NewJersey,Worcester(MA),andToronto(Ontario,Canada).ItwassuccessfullyeradicatedfromtheChicagoareafollowingalengthyandaggressivecampaignofdetectionandremovalofinfestedtrees(AntipinandDilley2004).
ThisbeetleisaseriouspestinChina,whereitkillshardwoodtreesinroadsideplantings,shelterbelts,andplantations.IntheUnitedStatesthebeetleprefersmaplespecies,includingboxelder(A.negundo),Norway(A.platanoides),red(A.rubrum),silver(A.saccharinum),andsugar(A.saccharum)maples.Otherpreferredhostsarebirches(Betulaspp.),Ohiobuckeye(Aesculusglabra),elms(Ulmusspp.),horsechestnut(Aesculushippocastanaeum),andwillows(Salixspp.).Occasional-to-rarehostsincludeashes,Europeanmountainash(Sorbussp.),Londonplanetree(Platanussp.),mimosa(Albiziajulebrissin),andpoplars(Populusspp.).AcompletelistofhosttreesintheUnitedStateshasnotbeencompiled.
Asianlonghornedbeetlesproduceonegenerationperyear.AdultbeetlesareusuallypresentfromJulytoOctober,butcanbefoundlaterinthefalliftemperaturesarewarm.Adultsusuallystayonthetreesfromwhichtheyemergedordisperseshortdistancestoanewhosttofeedandreproduce.Eachfemaleusuallyproduces35to90eggs(ormore)duringherlifetime.Eggshatchin10to15days.Thelarvaefeedunderthebarkinthelivingtissueoftheirhostandthenboredeepintothewoodtopupate.Adultsemergebyboringatunnelandcreatingalargeroundexitholeinthetree(USDAForestServiceandAnimalandPlantHealthInspectionService2008).
Currently,theonlyeffectivemeanstoeliminateAsianlonghornedbeetleistoremoveinfestedtreesanddestroy
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thembychippingorburning.Topreventfurtherspreadoftheinsect,quarantinesareestablishedtopreventtransportationofinfestedtreesandbranchesfromthearea.Earlydetectionofinfestationsandrapidtreatmentresponsearecrucial.Systemicinsecticidescanprovideprotectionforindividualtreesorsmallnumbersoftrees,butindividualtreetreatmentisnotfeasibleinforestedsettings.
ThefutureimpactofAsianlonghornedbeetlesonsouthernforestsisunknownforseveralreasons.First,thepestmayormaynotspreadintotheSouthoverthenext50years.Significanteradicationandcontainmenteffortsarebeingpursuedinareaswheretreesareunderattack.Althoughthebeetledispersesslowly—itdoesnotflygreatdistancesandtendstoremaininthesameareauntilhostsareexhausted—itmaybespreadgreatdistancesinfirewoodorbymovementofotherinfestedmaterial.
Awidevarietyofsouthernhardwoodtrees(especiallymaples)isatrisk.Itisunlikely,however,thatvastareasofhardwoodswouldbekilledwithinthenext50yearsbecausethebeetletakesseveralyearstokillhosttreesanditisaslowdisperser.Ifspotinfestationsarediscoveredearlyenough,thebeetlecanbeeradicatedbeforeitbecomeswidelyestablished.Successfuleradicationeffortsrequiremuchtime,funding,personnel,andstrengthofwill.
EffectsofsouthernclimateonAsianlonghornedbeetlearecompletelyunknown.ExtremeheatinsomepartsoftheSouthmayinhibitactivityandsuccess.However,thereisalsothepossibilitythatwarmertemperatureswouldleadtoquickercompletionofthebeetle’slifecycle,whichwouldmeanlargerpopulationsandmoredamagetosoutherntrees.
Baldcypress leafroller—Formerlynamedthefruittreeleafroller,thebaldcypressleafroller,Archipsgoyerana,periodicallydefoliatesbaldcypressinLouisianaandMississippi.Kruse(2000)describesthebaldcypressleafroller,andsummarizesitsbiologyanditseffectsonitshost.Thisnativeinsectcausesgrowthreductionanddieback,butonlycausesmortalitywhenmultipleotherstressorsareatwork.
Thebaldcypressleafrollerwasfirstrecordedin1983inLouisiana,whereitfeedsalmostexclusivelyonbaldcypress.Itannuallydefoliatesanaverageof35,000acresintheoak-gum-cypressforesttype.Althoughthisinsectismainlyapestoffloodedbaldcypress,itcanmoveintodrieruplandandurbansettingsduringperiodsofheavyinfestation.
Baldcypresstreesofallsizesdisplaycanopydiebackandsignificantreductionsindiametergrowthresultingfromrepeatedannualdefoliation.Pole-sizedtosmallsawtimber-sizedtreesgrowingonforestedgesorindensestandsaremostseverelyaffected.Inareaswherechronicsaltwater
intrusionisaproblem,treesdieafterasfewastwoconsecutiveyearsofdefoliation.
Temperatureandprecipitationchangesareunlikelytodirectlyaffectbaldcypressleafroller’sactivityandimpacts.However,highersealevelsresultingfromwarmertemperatureswouldfurtherstressbaldcypresstreesbecauseofincreasedsaltwaterintrusion,significantlyincreasingthelikelihoodthatdefoliationwoulddamageandkillhosttrees.HumanalterationstosouthernLouisiana’shydrology,greatersaltwaterintrusion,nutriafeeding,defoliationbybaldcypressleafroller,andotherstressorsareallcombiningtothreatenthebaldcypressresourceinsouthernLouisiana.Althoughunlikelytodisappearinthenext50years,thisresourceisexpectedtocontinuetobecompromised.
Emerald ash borer—Emeraldashborer,Agrilusplanipennis,isadevastating,wood-boringbeetlenativetoAsia.ItwasfirstfoundinfestingtreesinNorthAmericainsoutheasternMichiganandadjacentareasofOntario,Canada,in2002(Various2010).WithinthecoreinfestedareaofMichigan,Indiana,andOhio,morethan50millionashtreesareestimatedtobedead,dying,orinfested(Smithandothers2009).Elsewhere,theemeraldashboreralreadyhaskilledtensofmillionsofashtrees,andcontinuestoposeaseriousthreattotheashresourceofNorthAmerica.
TheemeraldashborerwasfirstfoundintheUnitedStatesin2002,butitwaslikelyintroducedintotheareaaroundDetroitintheearly1990s(Kovacsandothers2009),probablyinsolidwoodpackingmaterialfromAsia.Soonafterdetection,fivecountiesinMichiganwereplacedunderquarantine.However,intheyearsbeforedetection,infestedmaterial—suchasnurserystock,unprocessedashlogs,firewood,andotherashcommodities—wasmostlikelymovedtomanyareasaroundtheUnitedStates.InadvertentmovementbyhumanscontinuesintothepresentinspiteofFederalandStatequarantinesrestrictingtheexportofpotentiallyinfestedmaterialsoncetheborerisdetectedinacounty(U.S.DepartmentofAgricultureAnimalandPlantHealthInspectionService2003,2006).Surveysmadein2003foundinfestationsin12countiesinMichiganand3countiesinnorthernOhio.Byearly2011infestationswerelocatedinanadditional13States:Indiana,Illinois,Iowa,Maryland,Pennsylvania,Missouri,Virginia,WestVirginia,Wisconsin,Kentucky,Minnesota,andNewYork(fig.16.2).InCanada,infestationsnowoccurinseveralareasofOntarioandQuebec(USDAAnimalandPlantHealthInspectionService2011).
Sinceitsintroduction,theemeraldashborerhashadasignificantnegativeimpactontheecologyandeconomyofinfestedareas,withall16speciesofNorthAmericanashappearingtobesusceptible.AshtreesareanimportantpartoftheruralandurbanforestsoftheUnitedStates,valuedatmorethan$282billion(USDAAnimalandPlantHealth
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detectinfestationsearlyenoughtoeffectivelycontrolthemandpreventtheirspread.
Thereareanumberofeffectivechemicalcontroloptionsavailabletoprotectindividualtreesfrominfestation(Hermsandothers2009).Unfortunately,availabletime,funding,equipment,andexpertiselimitthenumberoftreesthatcanbeprotectedtourban/suburbansettingsandaverysmallnumberofhighvaluetreesinforestedsettings.Withtheemeraldashborerdestroyingeveryashinitspath,onepracticaloptionmaybetodelineateandprotectsmallpocketsofexceptionalashresourceas“ashconservationareas.”
Severallarvalandeggparasitoidsarebeinginvestigatedforuseasbiologicalcontrolagents(USDAAnimalandPlantHealthInspectionServiceandothers2010).Althoughresultsarepreliminary,itisreasonabletoexpectthatbiologicalcontrolagentswouldmitigatepopulationsbutwouldnotcontrolorcompletelystopthespreadandimpactsofthisinsectinvader.
Theeffectsofchangesinclimate—suchasincreasesintemperature,precipitation,andcarbondioxide—onemeraldashborerareuncertain.Warmertemperatureswouldlikelyresultinmorerapidlifecyclecompletionresultinginincreasedpopulationgrowthandimpacts.However,theextremeheatofsouthernsummerscouldactuallyinhibitactivityandreducetheamountofashmortality.TherangeofashtreesintheSouthisexpectedtoshrinkastheclimatewarms;betweenclimatestressandtheemeraldashborerinfestations,theSouthislikelytolosemillionsofashtreesinthenext50years.
Forest tent caterpillar—Foresttentcaterpillar,Malacosomadisstria,occursthroughoutmostoftheUnitedStatesandCanada,whereitdefoliatesavarietyofhardwoods(BatzerandMorris1978,Drooz1985,Fitzgerald1995,USDAForestService1985b).IntheSouth,itheavilydefoliateswatertupelo(Nyssaaquatica),sweetgum(Liquidambarstyraciflua),blackgum(N.sylvatica),andvariousoakspecies(Quercusspp.).ThemostpersistentandextremeoutbreaksintheSouthoccuronhosttreesinbottomlands,forestedwetlands,andriparianareas.Whenpopulationsreachepidemiclevels,thecaterpillarsoftenspreadtourbanandsuburbanareaswheretheydefoliateshadetreesandornamentalplants.
OutbreaksoccurinseveralSouthernStates,wheremorethan500,000acrescanbedefoliatedinasingleseason;defoliationdoesnotcausesignificantamountsoftreemortalityandthereforecontrolpracticesarerarelycosteffective.However,significantlossoftreegrowthisoftenanoutcome,andrepeated,heavydefoliationofstandsmaycausesignificantdieback.Ifneeded,controltechniquesareavailableand
haveproveneffectivebutdependontheavailabilityofbothfundingandtechnicalexpertise.
Tentcaterpillarimpactsoccurmainlyinthebottomlandhardwood-cypressforesttypes(mappedasoak-gum-cypressandelm-ash-cottonwood),buttheyoccasionallyoccurinuplandnorthernhardwoodforesttypes(mappedasmaple-beech-birch,oak-hickory,andoak-pine).
Changesintemperatureandprecipitationareunlikelytoincreasedefoliationbyforesttentcaterpillars.Ifclimatechangesignificantlystressestheforesttypesmostvulnerabletotentcaterpillardefoliation,theadditiveeffectofmultiplestressorscouldmeanhastenedorincreasedtreemortality.
Gypsy moth—Gypsymoth,Lymantriadispar,isnativetoEuropeandAsia.In1869,LeopoldTrouvelotintroducedtheEuropeanstrainofthegypsymoth.Sincethen,ithasspreadacrossthelandscapeoftheeasternUnitedStates,defoliatingvastacreagesofforest(USDAAnimalandPlantHealthInspectionService2010b).TheinsectwasfoundinnortheasternVirginiaintheearly1980s.Atitscurrentrateofspread,specialistspredictthatasignificantportionoftheSouthwillbeinfestedinthenext50years.
Theimpactofrepeatedgypsymothdefoliationonthehealthofoakforestsissignificant(CampbellandSloan1977).Repeatedseveredefoliationofoaksweakenstreestosuchanextentthattheymaybeattackedandkilledbysecondarypestorganisms,suchasthetwo-linedchestnutborer(Agrilusbilineatus)andArmillariarootrot(causedbyArmillariamellea).Extendeddroughtintensifiesthedeathrate.
Gypsymothcaterpillarsfeedonawiderangeoftreesandshrubs(Liebholdandothers1995,Zhu1994)butpreferoaks.Speciesareattackedpreferentiallywithoutrespecttoforesttype.Highlyfavoredspeciesincludesweetgum,northernredoak(Quercusrubra),andAmericanbasswood(Tiliaamericana).Speciesoflimitedsuitabilityincludepines,maples(Acerspp.),ash(Fraxinusspp.),Americanbeech(Fagusgrandifolia),andcherry(Prunusserotina).Speciesthatarenotfavoredorareavoidedincludeblackgum,yellow-poplar(Liriodendrontulipifera),blacklocust(Robiniapseudoacacia),baldcypress(Taxodiumdistichum),magnolia(Magnoliagrandiflora),andtupelo(Nyssasylvatica).Asgypsymothmovessouthandwest,itwillencounterlowerconcentrationsofoakandcovehardwoods,andforestsusceptibilitywilldecreaseinmanybutnotallareas.However,withitswidehostrangeitshouldstillpersist.
Themostimportantdiseaseagentsaffectinggypsymothsarethegypsymothnucleopolyhedrosisvirus(LdMNPV)andthegypsymothfungus,Entomophagamaimaiga(AndreadisandWeseloh1990,Hajekandothers1990).
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TheSlowtheSpreadProgramdecreasesthegypsymoths’rateofspreadfromapproximately25milesayearto7to10milesperyear(Sharovandothers2002).Iftheprogramcontinues,wecanexpectthegypsymothtomove350to500milesfartherintotheSouthoverthenext50years,comparedtototalinfestationwithin25to30yearswithouttheprogram.
Gypsymothscanalsobeartificiallyspreadbyhumanactivities;continuedvigilancetodetectanderadicatetheresultingsmallinfestationshelptopreventthemoth’srapidspreadintoallareasoftheSouth.Inaddition,methodsexisttosuppressareasofhighpopulationsininfestedareasandtoeradicate“satellite”infestationsinadvanceofthemoth’smovingfront;thesemethodsincludeaerialapplicationsofBt(Bacillusthuringiensis)ordimilin(insecticides),orpheromoneflakes(todisruptmating).
Temperaturechangesaloneareunlikelytohaveadramaticeffectongypsymothmovementorimpacts.Therangeofgypsymothinfestationisexpectedtoexpandregardlessofchangesinclimate,andataratefasterthancanbeattributedtoanypotentialclimatechange-causedhostrangeexpansion.Ifwarmertemperaturescausetheoak-hickoryforesttypetodisplaceborealforestsathigherelevationsintheSouth,gypsymothimpactswilllikelyincreaseintheseareas.
However,onehypothesisisthatgypsymothspreadanddamagewilldecreaseastemperatureswarm,therebyreducingtheextentofsouthwardspread.Gypsymothsneedacoldsnaptosynchronizehatches(avoidsdifferentlifestagesfromoccurringatthesametime)andthusimprovematingefficiency.2Ifthishypothesisiscorrect,asthemothmovesfarthersouthandasthetemperatureswarm,winterswouldnotbecoldenoughorthenecessarycoldsnapwouldcometoolateintheyeartosynchronizethespringhatch.
Adrierclimatewouldlikelyincreasegypsymothimpactsbecauseitwouldstresshosttreesanddiscouragebuild-upofthemoth’sfungalpredator,whichthrivesduringwettersprings.
BecausethegypsymothisstillspreadingintotheSouth,barringunforeseencircumstanceswecansaywithcertaintythatitsimpactswillincreaseoverthenext50years.Howsevereandwidespreadtheimpactswillbe,however,isdependentonmanyfactorsincluding:thecontinuationofactiveprogramstoslowthespread,suppressanderadicategypsymoth;theamountandhealthofhardwoodforeststhemothencountersinthefuture;andpotentialunknowntemperatureandmoistureeffectsonthemoth,itshosts,anditsnaturalenemies.
2JohnGhent,USDAForestService,ForestHealthProtection,200W.T.WeaverBlvd.,Asheville,NC28804,828-257-4328,[email protected]:May11,2010.
Hardwood borers—InsectborersareimportantpestsofhardwoodtreesthroughouttheSouth.Theytunnelinthebark,trunks,terminals,androots,causingavarietyofdefectsinwood,stemdeformity,reductionofseedproduction,andtreedecline.
SomeofthemajordamagingborersintheSouth(Solomon1995)arethecarpenterworm(Prionoxystusrobiniae),redoakborer(Enaphalodesrufulus),whiteoakborer(Goestigrinus),redheadedashborer(Neoclytusacuminatus),poplarborer(Saperdacalcarata),oaktimberworm(Arrhenodesminutus),Columbiantimberbeetle(Corthyluscolumbianus),andambrosiabeetle(Xyleboruscelsus).Borersthatareendemictoanareadonotnormallycausediebackandmortality,butinabnormallylargenumberstheycontributetotreedeclineandstanddegradation.Excessivenumbersofgrowthdefectscausedbyborersaffectbetween25and88percentofallhardwoodlogs(WardandMistretta2002).
Intheearly2000s,prolongeddroughtscompromisedthevigorofoaksinnorthernArkansas,leadingtoamassiveredoakboreroutbreak.Althoughtheywerenottheprimarycauseoftheoakmortalityinthatarea,theborerssoonbecamethemostdestructiveagentinthedeclinecomplex.Morethan340,000acresofoakandmixed-oak-pineforestwereseverelyimpacted,withanestimatedlossof500millionboardfeet(morethan$29million)ofoak.
Temperaturechangebyitselfisunlikelytohavemucheffectonhardwoodborerpopulations.Assecondaryinsectpests,theseborersareexpectedtohaveincreasedimpactaspopulationsofhardwoodageanddecline,especiallyduringperiodsofdroughtstress.HardwoodboreractivityanddamageislikelytoincreasethroughouttheSouthoverthenext50yearsifcurrentpredictionsoffutureclimatechangeproveaccurate.
Soapberry borer—Soapberryborer,Agrilusprionurus,anativeofMexico,wasfirstconfirmedineasternTravisCounty,Texas,in2003.Itinfestsandkillswesternsoapberry(Sapindussaponariavar.drummondii),itsonlyknownhost.Reportsbylandownersandarboristsindicatethattheinsecthadprobablybeeninfestingsoapberrytreesforseveralyearspriortobeingidentified.InfestedtreeswereobservedinTravisandMcLennancountiesasearlyas1998.ByJanuary2009,infestationshadbeenreportedin18Texascounties,includingareasnearFortWorth,Dallas,Waco,CollegeStation,Austin,Houston,andCorpusChristi.ByDecember2010,thenumberofcountieshadincreasedto43(Billings2011).3TodatenoinfestationshavebeenobservedinadjacentStates,althoughinfestationsinRobertsCountyintheTexaspanhandleand
3R.Billings,TexasForestService,ForestHealthunit,200TechnologyWay,Suite1281,CollegeStation,TX77845-3424,979-458-6650,[email protected]:March8,2011.
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WichitaCountyontheTexas-OklahomabordersuggestthattheinsectmayalreadybeinOklahoma(fig.16.3).
AssoapberryborerpopulationsexpandrapidlyinTexas,thiswood-boringbeetleiskillingallsoapberrytreeslargerthan2inchesd.b.h.Methodsofpreventionandcontrolarebeinginvestigated.Amongthemostpromisingisinjectionofasystemicinsecticide(emamectinbenzoate,registeredforthecontrolofinsectsonconifersandhardwoods,includingthepreventionofemeraldashborer)intouninfestedsoapberrytreesorthoseinearlystagesofattack.Test-injectiontreesarestillbeingmonitored,butearlyresultslookpromising.
Regardlessofclimatechange,itislikelythatwithin50yearstheinsectwillthreatenwesternsoapberrypopulationsthroughoutthetree’sentirerange,whichextendsfromnorthernMexicotoMissouri,andwesttoArizona.
Diseases of Softwoods
Annosum root disease—Annosumrootdisease(ARD),causedbythefungusHeterobasidionannosum(recentlyproposedtoberenamedH.irregulare(OtrosinaandGarboletto2010),producessignificantlossesofconifersacrosstheSouth.Onsandy,well-drainedsites,thisdiseasecausesgrowthlossandmortality.Itismostoftenassociatedwiththinningofloblolly,longleaf,shortleaf,slash,andwhitepineplantations.Thefunguscommonlyinfectsfreshstumpsandthengrowsthroughrootgrafts(rootsthatcomeintophysicalcontactandthengrowtogether,sharingwaterandnutrients)andinfectsresidualtreesonthesite.SlashandloblollypinesarethemostcommonlyplantedspeciesintheSouthandarebothverysusceptibletoARD(Robbins1984,Stambaugh1989).
AsurveyintheSouthdocumented:44to60percentoccurrenceofthisrootdisease;and2to3percentmortalityinplantedpine.Radialandheightgrowtharesignificantlylessfordiseasedpines(Applegate1971,Froelichandothers1977,Morris1970).
TheprimaryriskfactorsassociatedwithARDaretheamountofhosttypeavailable,thesoiltypeandcondition,andthetiminganddegreeofmanagementactivity.Riskdecreasesasclaycontentinthesurfacelayerofsoilincreases,aconditionthatenablesriskmapping(WardandMistretta2002).IntheSouth,riskofARDishighormoderatelyhighonanestimated163.5millionacres,notallcurrentlyforested(Hoffardandothers1995).
TherangeofARDalreadyextendsthroughoutsouthernforestsandintotheborealforestsoftheNorth,makingspreadunlikely.Indeed,itsrangecoulddecreasewitheffortsbymanylandmanagementagenciestorestorethelesssusceptiblelongleafpinetoitspreviousrange
whileconcurrentlypotentialdrought/temperaturerelateddiebackinthesouthernmostpartoftheloblolly/slashpinerangefurtherdecreaseitsrange.Increasedtemperatures,reducedrainfall,andincreasedhostgrowth(frommorecarbondioxideintheatmosphere)wouldallproducesomeincreasesindiseaseactivityresultingfromincreasedhostsusceptibility,butwouldnotsignificantlyincreasefungusvirulence.Itisimprobablethatclimatewarming/dryingwouldaffectpinesusceptibilityonwell-drained,sandysitesandforestedoldfarmfieldssinceonthesesitespotentiallyaffectedpinesarealreadyhighlysusceptibletothedisease.
Managementfordiseasepreventionusingboraxasastumptreatmentinuninfectedstandsshouldcontinuetobeeffective.Dependingontherateoftemperatureincrease,insolation(thermaltreatmentofthestumpsbythesun)maybeeffectiveinpreventinginfectionviastumpsfurthernorththanthe35thparallel,whichisthecurrentlyacceptednorthernlimitofitseffectiveness.
LossofareabyhostspeciesfavoredbyH.annosumshouldleadtoaslightoveralllossofthenegativeimpactofthisdiseaseoverthenext50years.
Brown spot needle disease—Brownspotneedledisease,causedbythefungusScirrhiaacicola,isconsideredthemostdamagingdiseaseoflongleafpine.Itprimarilyaffectsseedlingsbydelayingtheonsetofheightgrowthandcausinglossofpotentialwoodproductionandmortality(ifinfectionissevere).Brownspotissomewhatadiseaseofopportunity:thegrassesthatcompetewithlongleafseedlingsalsomaintainahumidmicroclimatethatcontributessignificantlybothtoinfectionoftheseedlingandtothegeneralsuccessofthedisease.
ThisdiseaseoccursfromVirginiatoTexas,primarilyontheCoastalPlain.Itismoresevereincertaingeographicareas(WardandMistretta2002).Useofcontrolledfirestoremovecompetinggrassesandeliminatedampnessishighlyeffectiveforcontrollingthediseaseandencouragingearlygrowthofseedlings,providedstepsaretakentoavoidsubsequentcolonizationbycompetingnon-nativessuchascogongrass.
Atpresent,longleafpineoccupiesonlyabout5millionacresofitsformer60millionacrerange.Recentrestorationeffortshaveledtotheproductionofhealthierseedlingsforplantingandplantingsuccesshasimprovedonsiteswherelongleafwasoncethedominantspecies(Cordellandothers1989,Kais1989).Overthenext50years,theemphasisonlongleafpinerestorationshouldhaveagreaterimpactonthisdiseasethanclimatewarming.LongleafpineiswelladaptedtosummertemperaturesintheSouthanditisunclearthatincreasesevenashighas1oCwouldhavesignificantimpactonthesouthernextentofthelongleafpinerange.Highertemperaturesmightslightlyfavorincreaseingrowthand
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longersummerheatspellsmighttriggerearlyonsetofheightgrowthfromthegrassstagetothecandlestage,endingthepotentialforbrown-spotdamagesooner.Reductionsinrainfall,dew,andfogshouldfavorthelongleafpineoverthefungalpest.Noshiftinaggressivenessofinfectionorvirulenceofthepathogenisforeseen.
Weanticipateasignificantincreaseintheincidenceofbrownspotdisease.Thisexpectationisbasedmoreonincreasedout-plantingoflongleafpineseedlingsthanonclimateinfluences.Thus,althoughclimatechangeisnotexpectedtosignificantlychangethediseaseprofile(itsvirulenceorhostspectrum),humaninterventiontoincreasethequantityofhosttreescouldresultinincreasedincidence.
Fusiform rust—Fusiformrust,causedbythefungusCronartiumfusiformef.sp.fusiforme,occursprimarilyonslashandloblollypines.Itisconsideredthemostdestructivediseaseofsouthernpines,causingtheproductionofcigar-shapedgallsthataregenerallyfatalifformedonthemainstemofthehost(Andersonandothers1980,Czabator1971).
Extensiveplantingofsusceptibleslashandloblollypinessincethe1930shasresultedinanepidemicoffusiformrust,whichnowextendsthroughoutitsavailablehostrangeintheSouth;infectedtreesbeingfoundthroughoutthesouthernpineregion(WardandMistretta2002).LossesaremostseriousonCoastalPlainsitesfromLouisianatosoutheasternSouthCarolina.Severalvariablesincludingweather,amountofinoculum,abundanceofoaks(thealternatehost),andsusceptibilityoftheindividualpinespeciesgovernincidenceofthedisease.Effectivestrategiesareavailableformanagingfusiformrustimpactinplantationsandforestsincludingavoidanceofover-fertilizingseedlingsinthenursery,silviculturalmanipulationofyoungstandstofavorhealthysaplings,andfavoringthedeploymentofgeneticallyscreenedresistantseedlingsinareasofhistorichighrustincidence.
Increaseindiseaserangeinthisregionundertheinfluenceofawarmer,drierclimatechangescenarioisnotaconcernsincethediseaseisalreadydistributedhost-rangewidewithintheregion.However,increasedtemperatureandcarbondioxideintheatmospherecouldcausethepathogentobecomemorevirulentonitscurrenthostbase.Althoughthereissomedisagreementontheeffectofprojectedwarmer,drierclimateregimesonthegeographicrangesforthepinehosts,itisanticipatedthatanylossesofpineincoastalareaswouldbematchedbygainsinthePiedmontandinthelowerreachesoftheAppalachianMountains.
Althoughresearchonrustfungiisinconclusiveandprimarilybasedoncerealgrainsandotherfieldcrops,resultssuggestthattherewouldbegreaterincidenceoffusiformrustsimplyasafunctionofhealthierfungusandhosttrees(Chakrabortyandothers1998).Wealsoanticipatethat
loblollypineatleastwillbeplantedinareasnorthofitscurrentrange;andthattherust,whichinfectsjuveniletissue,willrapidlyfollowintothesenewlyplantedareas.
Overthenext50yearsgiventhegeneralavailabilityofoakalternatehostsforthefungusandtheonlyslightpredictedmigrationofpinefromcoastalareasupwardintotheAppalachianMountains,weexpectthatthepathogenwillsuccessfullyfullycolonizetheextendedrangeofitshosts.Thepotentialeffectofoutplantingrustresistantseedlingsinconjunctionwithpotentialgeographicrangeandclimateshiftsisuncertainatthepresenttime.Iftheresistanceismaintainedinthefaceofchangingconditions,areductionoftheimpactofthisdiseasewouldbeexpectedtooccur.
Littleleaf disease—LittleleafdiseaseisthemostseriouspestofshortleafpinesintheSouth.Itiscausedbyacomplexoffactorsincludinganonnativefungus(Phytophthoracinnamomi),lowsoilnitrogen,erodedsoils,poorinternalsoildrainage,andaplowpan—acompactedlayerofsoilthathasbecomelessporousthanthesoilaboveorbelow,generallytheresultoftillingorotherfarmingoperations(CampbellandCopeland1954).Often,nativenematodes(microscopicroundworms)andnativespeciesofPythium(alsoafungus)areassociatedwiththedisease.Infectedtreeshavereducedgrowthratesandcommonlydiewithin12yearsofsymptomonset.
P.cinnamomiisdistributedthroughout(andwellbeyond)therangecurrentlyoccupiedbyshortleafandloblollypineintheSouth.Shortleafpineisthemostseriouslydamagedsoftwoodhost,withloblollypineaffectedtoalesserextent;Americanchestnutwasitsprimaryhardwoodhost.LittleleafdiseasehasalsobeenreportedonVirginia,pitch,slash,andlongleafpines.AffectedpinestandsarefoundonthePiedmontfromVirginiatoMississippi.ThediseasehasitsgreatestimpactinAlabama,Georgia,andSouthCarolina(WardandMistretta2002,fig.17.10),withadditionalscatteredpocketsoccurringineasternTennesseeandsoutheasternKentucky.Notethat,althoughthefungus’rangeexceedstherangeofitspinehosts,littleleafdiseaseisfurtherrestrictedinwithinthatlargerrangegenerallybysiteconditions.
Thefungushasamobilesporeandneedswatertospreadfromandinfectedhosttouninfectedpotentialhosts;however,thediseasethrivesunderdryconditionsthatstressthehost.Controlstrategiesareavailablebutmost—suchassanitationthinningandsalvagingdeadmaterials—relyontreatmentafterinfectionwhendamageisimminentoralreadyoccurring.
Becauseofitsspecificsiterequirements,spreadintouninfectedsouthernforestsisnotexpected.Further,rehabilitatingsitesbybreakingupoftheplowpansthat
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favorthisdiseaseshouldresultinbetterwaterrelationsandareductionininfections.Anincreaseinatmosphericcarbondioxidewouldresultinincreasedgrowthofthehostandgreaterdiseaseexpressioninaffectedtrees.Lossestothisdiseaseshouldcontinueatthesamerateonaffectedsites.However,itsrangeshouldcontractifincreasedtemperaturescauseitshoststomigratenorth,anditsimpactshoulddecreaseovertimeassitesarerehabilitated.
Loblolly pine decline—Reportsofsparse,yellowingcrowns,andlowannualwoodproductioninthepinesofcentral-to-northernAlabamadatebacktothelate1960s(BrownandMcDowell1968,Brownandothers1969).Sincetheearly1990s,localizedincidentsofdecliningpineshavebeenoccurringthroughoutAlabamaandintosouthwesternGeorgia,withadditionalsymptomsincludingrootmortalityanddiscolorationofmanyofthesurvivingrootlets(Hessandothers2003).Recentliteraturesuggeststhepresenceoffungi—includingLeptographiumserpens,L.terebrantis,andL.lundbergii–intherootsofaffectedtrees(Eckhardtandothers2004b);butwhethertheyareprimarypathogensorsimplytakingadvantageofalreadysignificantlyweakenedtreesisstilluncertain.Abarkbeetle,Hylastessp.,hasbeenfoundintherootsystemsofmanydecliningpines,andissuspectedofvectoringthefungusfrominfectedtouninfectedtrees(Eckhardtandothers2004a).Informationislackingonwhethertheyselectweakenedtreestoattackorareindiscriminateintheirattacks(whichwouldsuggestthathealthytreesmaybeabletoovercomesuccessfulinoculation).
Thesymptomsofthedeclineprimarilyoccurinloblollypinesolderthan40years,firstbecomingapparentintreesinthe40to50yearageclass.Mortalitycanoccurbeginningaslittleastwotothreeyearsafterfirstsymptomexpression.LittleisknownaboutthepotentialrangeandseveritybeyondthatfromfieldsurveysincentralnorthernAlabama(Hessandothers2005)andFortBenning,Georgia(Menardandothers2006).Nevertheless,thereisstrongspeculationthatbothabioticandbioticfactorsareinvolvedinpredisposingaffectedstandstodecline.Thesefactorsincludeclimate,wildfire,andhumandisturbancessuchaspreviousagriculture.Coincidently,manyuplandsitesinnorthernandcentralAlabamawereoriginallyconvertedfromsubsistencefarmingtoloblollypineplantationbecauseofloblolly’sout-plantingsuccessrateanditsrapidgrowth.Onetheoryisthatmanyofthesesitesaresimplyunabletosustainsuchrapidgrowthoverthelong-term.
Despitetheuncertaintiesaboutthecausesandprogressionofthisdiseasecomplex,managementstrategiesareinplacethatcanbeimplementedwiththeexpectationofimprovingresistanceoffuturestandsonaffectedsites.Thesestrategiesstartwithapplyingariskratingmodelthatusesdigitalelevationmapsandmappedshapefilesforthesitesin
questioncombinedwithdataonlandformandroothealthofthetreesinthestand.Ifthemodelpredictshazardtoloblollypine,therecommendedalternativespeciesislongleafpine.Forexistingloblollypinestandsonhighhazardsites,therecommendationistothinthembetweenages20and40(Hessandothers2003).Apreviousrecommendation,toallowahigh-risksitetorevertbacktonativehardwoods(Loomis1976,Miller1979),isstillaviable(butseldomadopted)managementoption.
Treedeclineislikelytoincreaseinawarmeranddrierclimate,regardlessofinputsfromdiseaseandinsectvectors.Thisresponsetochangingclimateisamajorfactorinthenorthwardmovementprojectedforthesouthernpines.Increasingincidenceofdeclineshouldeventuallydiminishasnewadaptedecosystemsformintheregion,butthisisnotexpectedtooccurwithinthenext50years.
Diseases of hardwoods
Beech bark disease—Beechbarkdiseaseiscausedbyacomplexoftwoormoreagentsworkinginconcert.Thebeechscale,Cryptococcusfagisuga,attacksthebarkofAmericanbeech,creatinginfectioncourtswhicharesubsequentlycolonizedbythefungusNectriacoccineavar.faginata.Thisfunguscausescankersthatgrowtogetherandgirdlehosttrees.
WhilethebeechscaleisnowacommonpestoftheAmericanbeech,itisnonnative,havingbeenintroducedthroughtheCanadianProvinceofNovaScotiainthelate1800s.Thereisspeculationthatthefungusisalsoanintroducedspecies.Discussiononthatpointissomewhatpointlesssinceanativefungus,N.galligena,isalsocapableofincitingcankersandkillinghostsafterenteringthroughscale-damagedbark.Thescaleisconsideredthepivotalintroductionthatallowedtheinvasivespreadofthisdiseasecomplex(HoustonandO’Brien1983,SouthernAppalachianManandtheBiosphere1996).
Thisdiseasecomplex,firstidentifiedinsouthernforestsintheearly90s,continuestospreadalongabroadfrontandisexpectedtooccupytherangeofitshost(WardandMistretta2002).Intheearlyphaseofitscycle,morethanhalfoftheAmericanbeechtrees10inchesd.b.h.orlargerarekilled.Openingscreatedbydeathorremovalofthebeechresultindensestandsofroot-sprouts,whichproducestandsdominatedbybeechbutlackinganyofitsnormalassociates.Inthesecondphaseofthecycle,revegetatedbeechstandsareattackedlessseverely,resultingincankeredsurvivorsratherthaninextensivemortality.Treesinfectedinthisphasearerarelygirdled,buttheyaregenerallyseverelydeformed.
SincethisdiseasecomplexaffectsonlyAmericanbeech,thereisadirectrelationshipbetweentheamountofbeech
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inastandandtheintensityofthedisease.Houston(1997)reportsthatstandageanddensity,treesize,andspeciescompositionaffectdiseaseseverity,especiallyinforestsaffectedforthefirsttime.
Beechbarkdiseaseisenabledbyaninsectvector,sotheprojectionoffutureconditioniscomplicatedbeyondthatofasimplepathogenorinsectdrivenpestsystem.Vectormediationcorrespondstoavailabilityofsporesandhostsusceptibility,andisexpectedtomaintainsynchronicitysufficienttocauseaslightincreaseininfection.Temperatureintoleranceofthehostshouldreducethehost’sgeographicrangeinthefaceofclimatechange.Increasesincarbondioxideshouldincreasehostgrowthallowingaslightincreaseindiseasevirulence.
Ultimately,however,thereductioninavailablehosttreesshouldresultinanoveralldecreaseofsignificanceofbeechbarkdiseaseinsouthernforestsdespitetheprobabilitythatindividualtreeswillexperienceaslightincreaseindiseaseseverity.
Butternut canker—ButternutisbeingkilledthroughoutitsrangeinNorthAmericabyafungus,Sirococcusclavigignenti-juglandacearum,whichcausesmultiplecankersonthemainstemandbranchesofhosttrees.Butternutcankerhasbeenfoundin55countiesintheSouthextendingnorthfromnorthernAlabamaalongtheAppalachianMountainsintoNorthCarolina,Tennessee,Virginia,andKentucky,withscatteredoccurrencesthroughoutKentuckyandTennessee(WardandMistretta2002).ButternutnumbershavebeendramaticallyreducedandthespeciesisnowlistedasaspeciesofSpecialConcerninKentuckyandasThreatenedinTennessee(USDANaturalResourcesConservationService2011).InbothstatesthespeciesislistedasG4/S3.G4indicatesaplantwhichis“…apparentlysecureglobally,thoughitmaybequiterareinpartsofitsrange…”whileS3indicates“…rareanduncommoninthestate…”(USDANaturalResourcesConservationService2008,2009).
DetailedexaminationofcankersindicatesthatbutternutcankerhasbeenpresentintheUnitedStatessincetheearly1960s.Itsoriginisunknownbutitsrapidspreadthroughoutthebutternutrange,itshighlyaggressivenatureoninfectedtrees,thescarcityofresistanttrees,thelackofgeneticdiversityinthefungus,andtheageoftheoldestcankers(40years)supportthetheorythatitisarecentintroduction.DatafromforestinventoriesshowadramaticdecreaseinthenumberoflivebutternuttreesintheUnitedStates(77percentlossinNorthCarolinaandVirginia).
Becausebutternutmakesuplessthan0.5percentofthetreesintheSouth,theoverallcurrentimpactofitslosstotheforestedecosystemintheSouthisconsideredbysometobe
minor.However,asbutternuttreesdie,theyarereplacedbyotheralreadypresentspecies,contributingtoareductionofbiodiversity.
ClimatechangewouldlikelyraisetemperaturesatthehigherelevationsoftheAppalachiansandtheCumberlandPlateau.Thiscoupledwithdrierconditionswouldsignificantlyreducetherangeofbutternutatitssouthernedge.Althoughthehighertemperaturesandpredictedincreasesinatmosphericcarbondioxidecouldincreasethehosttrees’growth,drierconditionsresultingfromreducedprecipitationwouldactagainstthisincrease.OverallweexpecttoseemorecankeringandmortalityoccurringonfewerbutternuttreesintheSouth.
Chestnut blight—Introductionofthechestnutblightfungus,Cryphonectriaparasitica,fromAsia,probablyinthemiddle-to-late1890s,ledtoapermanentchangeinforestecosystems.TheAmericanchestnut(Castaneadentata)wasessentiallylost,notonlyasavaluabletimberspeciesbutalsoasthemostimportantproducerofhardmastforwildlife.Oaksandotherspeciesfilledthevoidsinforeststandsleftbythedeathofchestnut(Hepting1974,Oakandothers1998).Thefunguscontinuestosurviveoninfectedsproutsfromoldchestnutrootstock,variousoaks,andsomeotherhardwoods(Boyce1961).
Nocontrolwasfoundtostoptherapiddevastationcausedbythisblight,andthereislittlechancethatthepathogenwilldisappearorthattheAmericanchestnutwillnaturallyrecoveritspreeminentpositionineasternforests.Researchersintohypovirulencehavediscoveredadiseasethatweakenstheblightfungus,resultinginlessdamagetotheinfectedtree(Anagnostakis1978).Field-testingisunderwayonageneticallyengineeredvirusthatcausesahypovirulentreactionandhasthepotentialtoefficientlyspreadhypovirulencethroughoutthefungalpopulation.
AttemptstocrossAmericanchestnutswithorientalvarietiesandthenbackcrosstotheAmericanparentappeartoofferaviablemethodofmaintainingresistantchestnutinforests(Schlarbaum1988).SelectivelybreedingchestnutsasdescribedhasproducedchestnuthybridclonesthatareundergoingfieldevaluationbytheAmericanChestnutFoundation.Iftheseedlingsovercomeboththeblightandanotherdisease(causedbyPhytophthoracinnamomi)thatwasdevastatingchestnutsatthetimechestnutblightwasintroduced,aseriouseffortcanbemadetoreintroducechestnutintotheAmericanforests.Itistooearlyyettopredicttheoutcomeofthiseffort.However,evenifthehybridsareresistanttothedisease,largeareasofforestlandcannotberestoredtochestnutinthenext50yearsbecausetheseedlingsthatwouldbeneededforthateffortarenotexpectedtobeavailableinlargeenoughquantities.Further,ifclimatechangeisconsidered,theimpactsonchestnut
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deployedintherestorationeffortwouldprobablybesimilartothosepredictedforoakssufferingfromoakdecline.
Dogwood anthracnose—Dogwoodanthracnoseiscausedbyanintroducedfungus,Disculadestructiva.ItwasfirstreportedintheUnitedStatesonfloweringdogwood,Cornusflorida,in1978andonwesternfloweringdogwood,C.nuttallii,in1979.Forthepastthreedecades,floweringdogwoodshavebeendecliningataratethatthreatensimportantculturalaspectsofsouthernsociety.Insomeareas,theyhavebeenallbuteliminatedfromtheforestecosystemabove3,000feet(WardandMistretta2002).
Theeasternfloweringdogwoodisasmalltreevaluedbothasasignofspringforruralcommunitiesandforestvisitors,andasanimportantsourceofsoftmastforover100differentspeciesofwildlifethatfeedonitsberries(Kasper2000).Itistypicallyanunderstorytreefoundgrowingwithotherhardwoodssuchasoakandhickory.Severeinfectionisrestrictedtofullyshadedunderstorytreesathigherelevations(above3,000feet)andtothoseonshadedsiteswithanorthernexposure.Thehazardofsevereinfectionandmortalityisgreatestinshaded,moist,andcoolareas.
TherangeofthisdiseasestretchessouthwardintoSouthCarolinaandAlabamaandwestwardintocentralTennesseeandscatteredwesternKentuckycounties(WardandMistretta2002)withactivityconcentratedintheAppalachianMountains.ThesouthernmostlimitofthedogwoodanthracnoserangerelativetoavailablehosttreessuggeststhatthisdiseaseistemperaturelimitedintheSouth.Whetherthislimitationfunctionsatthetimeofsporepropagationordisseminationandhostinfection,orwhetheritactsdirectlytolimitdiseasesuccessisunclear.
Anyprojectedincreaseintheincidenceorvirulenceofdogwoodanthracnosebasedonincreasedhostandfungalgrowthresultingfromhighercarbondioxidelevelsintheatmosphereshouldbeeclipsedbythetemperatureincreasesandpossiblerainfallreductionsprojectedtooccurunderclimatechange.Increasedtemperatureandaridityencroachingathigher-than-currentelevationsintheAppalachianMountainsshoulddiminishtheimportanceofthisdiseaseintheregion,especiallyifithasreachedatemperaturebarrierfarthersouth.Arecolonizationofsomeareascurrentlydenudedofdogwoodbythisdiseasemightbepossible.
Dutch elm disease—TheDutchelmdiseasepathogenisvectoredbyoneoftwobarkbeetlesandcanbecausedbyeitheroftwocloselyrelatedspeciesoffungi:Ophiostomaulmi(formerlycalledCeratocystisulmi);andOphiostomanovo-ulmi,whichismoreaggressiveincausingdisease(Brasier1991).ThesefungiwerefirstintroducedtotheUnitedStatesondiseasedelmlogsfromEuropepriorto
1930.Itisunknownwhenthemoreaggressivespeciesbecameestablished;howeveritwaspossiblypresentasearlyasthe1940sto1950s,andmostlikelycausedmuchofthedevastatingelmmortalitythroughthe1970s.Thelessaggressivespeciesisbecomingincreasinglyrareinnature,andtheaggressivespeciesisthoughttobetheprimarycauseofcurrentmortality.Althoughsomelocalresurgencehasbeenobserved,thereisnoevidencethatthepathogenhasfurtherchanged.Localizedresurgenceismorelikelytheresultofdecreasedmonitoringandsanitationvigilance,abuildupinpopulationsoftheinsectvectors,orhighdensitiesofsusceptiblehosttreesinthewild(Frenchandothers1980,Haugen2007,Hubbes1999).
NativespeciesofNorthAmericanelmsvaryintheirsusceptibilitytoDutchelmdisease.Americanelm(Ulmusamericana)isgenerallyhighlysusceptibleTothediseasewhilewingedelm(U.alata),Septemberelm(U.serotina),slipperyelm(U.rubra),rockelm(U.thomasii),andcedarelm(U.crassifolia)rangefromsusceptibletosomewhatresistant.Nonativeelmsareimmune,butsomeindividualsorcultivarshaveagreaterresistanceorahighertolerancetoinfection(andthereforemayrecoveroratleastsurvive).ManyEuropeanandAsiaticelmsarelesssusceptiblethanAmericanelm(Haugen2007).
Inadditiontogeneticfactorspresentinsomecultivarsandspecies,physicalfactorsaffecttreesusceptibility.Thesefactorsincludeseasonoftheyear,climaticconditions(suchasdrought),andvitalityofthetree.Waterconductingelementsaremostsusceptibletoinfectionbecausetheyareproducedinthespring,makingsusceptibilityhighestfromfirstleafingtomidsummerandlowestduringdroughtconditions.Vigorouslygrowingtreesaregenerallymoresusceptiblethanslowergrowingtrees(D’Arcy2005).
Rootsofthesameorcloselyrelatedtreespeciesgrowingincloseproximityoftencrosseachotherinthesoilandeventuallyfuse(becomegrafted).Thefunguscanmovefrominfectedtreestoadjacenttreesthroughthesegraftedroots.Infectionsthatoccurthroughrootgraftscanspreadveryrapidlythroughoutthetree,becausethefungusiscarriedupwardinthesap.Rootgraftspreadisasignificantcauseoftreedeathinurbanareaswhereelmsarecloselyspaced(Frenchandothers1980,Haugen2007).
Currentmanagementoptionsinurban,suburban,andotherhighvaluesettingsincludesanitizingtoreduceinsectvectors,applyinginsecticidestokillinsectvectors,disruptingrootgrafts;injectingtreeswithfungicide,eradicatingthefungusfromnewlyinfectedtrees(pruning),andplantingresistantortoleranttrees(Frenchandothers1980,HaugenandStennes1999,Newhouseandothers2007,Schefferandothers2008).
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Althoughthemosteffectiveactionispromptremovalofstressed,dead,anddyingelms,thisintensityoftreatmentisoftennotfeasible(Haugen2007).
Despitethepresenceofseveralelmspecies(Americanelm,wingedelm,andslipperyelm,atleast)verylittleDutchelmdiseasecanbefoundinareasbelownorthernNorthCarolina,Tennessee,andArkansas.Itappearsthateitherthebeetlesorthefungiinvolvedintransmitting/causingthediseasearetemperaturelimited.Barringsignificantchangesinitspathogen/vectorcombination,increasingtemperatureandmigrationofthehostslightlytothenorthisexpectedtodiminishthedisease’soverallimpactintheSouth.
Laurel wilt—Laurelwiltisaninsect-vectoreddiseasethatiscurrentlydecimatingtheredbay(Perseaborbonia)populationofthesouthernCoastalPlain.ThisdiseasewasfirstidentifiednearPortWentworth,Georgia,in2003andhassubsequentlyspreadnorth,south,andinland(west)fromthatlocation(fig.16.4).Itiscausedbyanintroducedandonlyrecentlyclassifiedfungus,Raffaelealauricola,(Harringtonandothers2008)thatisvectoredfromhosttohostbyanambrosiabeetle(Xyleborusglabratus,alsoanintroducedspecies).Thebeetlecarriesthefungusinpoucheslocatednearitsmandibles.Whenthebeetleboresintothesapwoodthefungusinoculatesthexylem.Onceinoculated,thehostrapidlydevelopsavascularwilt;itsleavesdiegenerallydownwardfromthetop,andthewoodbeneaththebarkbecomesdiscoloredfromstreaking(Fraedrichandothers2008).Infectedhostsdisplayrapiddieback(wiltedleavesanddiscoloredsapwood)andmayormaynotexhibitextrusionoffrass(thefinepowderysawdustandexcrementthatinsectspassaswasteafterdigestingplantmaterial)fromtheinsect’sentryholes.
Severaladditionalhostshavebeenidentifiedforthisvectoreddiseaseincludingswampbay(Perseapalustris),sassafras(Sassafrasalbidum),avocado(Perseaamericana),camphor(Cinnamomumcamphorate),pondberry(Linderamelissifolia),andpondspice(Litseaaestivalis).Redbay,however,isthefavoredhostfortheambrosiabeetleandtothepresenttheseverestdamagehasbeenlimitedtoredbay(Hanulaandothers2008).
Atthepresenttimethereisnoeffectivecontrolknownforthisdiseaseforforestandwoodlanduse.Whilepreliminaryresultsusingpropiconazole(afungicide)showpromiseforpreventingthediseaseintreatedtrees,thenecessityofretreatingthemandthecostoftreatmentsuggeststhatinthefutureusemaybelimitedtotheprotectiononlyofhighvaluetrees(Mayfield2008).Researchintochemicaltreatment,centeredoncontrolofthevector,isongoingbuthasyettoidentifyachemicaleffectiveforthispurpose.Managementrecommendationsemphasizeearlysanitation(removal)ofkilledmaterialbutwiththestrongconcurrent
recommendationthatthedeadmaterialsnotbemovedoffsite,orifmovedoffsitethennotoutoftheknowninfested/infectedarea.Further,itisrecommendedthatwheneverpossiblematerialthathasbeencutdownshouldbechippedorburiedratherthanleftintact(Mayfield2008).
Basedonthecurrentrateofspread(estimatedtobeabout20milesperyear),theknowndistributionofredbay,andregionalclimateprojections,KochandSmith(2008b)haveextrapolatedprobablespreadofthisdiseasethrough2040(fig.16.5).Accordingtotheirprojection,thediseasecomplexwillhavereacheditsnorthernextent(hostbased)by2020,andwillreachthewesternextentofitshostrangeineasternTexasby2040.Thebasisoftheirprojectionsisthecombinationofredbay’snaturalrangeandclimaticbarriersthataffectthevectorandfungus,whichwilllikelystallfurtherprogressofthediseaseintheSouth.Theircaveatisthatprojectionsarelimitedtotheredbayhost.
Unansweredatthispointintimeiswhetherthisfungus/vectorcomplexcouldbecomeestablishedinotherpartsofthecountryonotherlauraceoushosts(suchastheCalifornialaurel)shouldfungus-carryingbeetlesbeintroducedintopotentialnewhostranges.Further,potentialforaffectingthespreadofandpossiblycontrollingsomeofthelossthroughimplementationoftheRecoveryPlanforLaurelWiltonRedbayandOtherForestSpecies(Mayfieldandothers2009)isasyetanunknownfactorinthemanagementofthisdisease.
Unfortunately,in2009,laurelwiltwasdetectedintheSandHillCraneNationalWildlifeReserveinsouthernMississippi—alocationthatwasnotpredictedbyKochandSmith(2008b)forinfectionuntilabout2017—apparentlythroughhumanintroduction.Regardlesswhetherthisisanewintroductionormovementfromtheeastcoastinfectedarea,ithasreducedby8yearsthedisease’sexpectedarrivalinTexas.
Ofconcerniswhetherthediseasemightexpanditshostrangeundertheinfluenceofclimatechangeorthroughamodificationofthefungus/vectorcomplexthatwouldallowanewinsectvectortobecomeinvolved.Ifeitheroccurs,thereisstrongpotentialforcurrentlyunpredictedinvolvementofnewhostsandunpredictedspread;newnessofthiscomplexintheSouthleadstoextremeuncertaintywhenattemptingtoprojectfuturebehavior.
Giventherapidandseveredamagedonetotheinfectedhostscoupledwithpredictedshiftsincoastalvegetationresultingfromprojectedtemperatureincreasesandpossiblydecreasingprecipitation,thepotentialofthisdiseasetospreadbeyonditsprojectedrangeishighlyuncertain.
Oak decline—Becauseofthehistoryofwoodsgrazing,widespreadwildfire,andexploitiveloggingforwood
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oakdeclineepisodescontinuetooccurintheregion(primarilyinArkansasandVirginia)wherepredisposingconditions,incitingevents,andcontributingfactorsarecoincident(Gysel1957,Oakandothers1988,Starkeyandothers2000).
Withincreasedtemperatureand(possibly)lessrainfallbeingpredicted,oakdeclineisexpectedtoincrease,possiblysignificantly.Declineresultingfromthestressesimposedshouldbecontributorytoeliminationofoakinsomedrierareas,anditisuncertainwhatcommunityofplantswouldreplacetheoakonthesesites.
Oak wilt—OakwiltisavascularwiltdiseaseofoaksthatisfoundonlyinNorthAmerica.Thecausalfungus,Ceratocystisfagacearum,wasfirstidentifiedinWisconsinin1942.ScientistsbelievedthediseasetobenativetoNorthAmericaandtohavebeenpresentlongbeforeitsdiscovery(MacDonald1995,TainterandBaker1996).Recently,strongspeculationhasbeenvoicedthatthefungusisactuallyanonnativeintroduction,possiblyfromSouthAmericawhereitoccurswithoutcausingdisease(Juzwickandothers2008).Oakwiltoccursin21CentralandEasternStates(RexrodeandBrown1983);9ofthe13SouthernStatesareknowntoharborthedisease,butseveremortalityislimitedtoarecentoutbreakincentralTexas(WardandMistretta2002).
Oakwiltcausesaffectedtreestowiltandusuallytodie.Allspeciesofoakaresusceptible,butspeciesintheredoakgroup—northernred(Quercusrubra),scarlet(Q.coccinea),andblack(Q.velutina)oak—aremostreadilykilled.Oaksinthewhiteoakgroup—white(Q.alba),post(Q.stellata),andchestnut(Q.prinus)oaks—areinfectedbutmortalityoccursmuchlessfrequentlyandmoreslowly.Liveoaks(Q.virginiana)dieatarategenerallyintermediatebetweenredandwhiteoaks.
Sap-feedingbeetlescancarryfungalsporestonearbyhealthytrees,thefunguscancolonizeneighboringuninfectedtreesbygrowingthroughrootgrafts,andhumanmediatedtransmissionisalsopossible(movinginfectedfirewoodwithintactbarkallowsfruitingofthefungusinareascurrentlynotinfected).
Itisunclearwhetherthenorth-to-southprogressofthediseasewashaltedbyatemperaturebarrierthatlimitsmigrationofthefungus.TheexistenceofsuchabarriercouldmeanthattheTexasoutbreakistheresultofarelativelyrecentadaptationofthefungustoahighertemperatureregimeoranadaptationtothehosts(liveoak)attackedinthatarea.RegardlessofwhatcausedtherecentsurgeinoakwiltactivityinTexas,itsrapidspreadraisesthepracticalquestionofwhetherthefunguscannowspreadthroughouttheuninfectedareasfromLouisianatoGeorgiaandFlorida.Weanticipatethatthisquestionmaybeansweredwithinthe
next10to20yearsasthediseaseappearstobespreading(orbeingspreadbyhumans)atafairlyrapidrate.
Increasingsoiltemperaturemightprovideafurtherbarriertospread,ifindeedtemperaturehasbeenabarrier.Predictingthedirecteffectsoftemperatureandatmosphericcarbondioxideonthisdiseasewillrequireanunderstandingofthepathogen-hostmechanismsatplay:whetherdamagetotherootsystemissufficienttocausesymptomsanddeath,orwhetherthefungusmustgrowfromtherootsystem(wheremostofthetransmissionisoccurring)intoandthroughoutthevascularsystemabovegroundtocausethesameeffect.
Littlecanbesaidwithanydegreeofcertaintyaboutpossibleinsecttransmissionofthisdisease.Consistentbutinefficienttransmissionbysap-feedingbeetles(NitidulidsandScolytids)isanacceptedmodeofspread.Shotholeborershavealsobeensuggested,butthese,andotherpossibleinsects,arelessaccepted.Longerperiodsofactivityoftheseinsects,resultingfromthelengtheningofsummers(alreadybeingobserved),couldgreatlyincreasetransmission.However,thisincreasecouldonlyoccuriffruitingmatsofthefungus(which,inTexas,isassociatedwithcoolerandmoisterfall,winterandspringconditions;nottheanticipatedconditions)werepresentduringthetimeinwhichtheinsectsareactive.UnlessincreasedtemperaturetriggersmorematformationthanhasbeenhistoricallyreportedinCentralTexas(unlikely),itisnotexpectedthatadditionalinsectswouldbecomesignificantcarriersofthefungustouninfectedtrees.Possiblelossofsomecoastalforesttosavannashouldhaveonlyaslightimpact:simplyreducingthenumberofhostslessensdiseaseincidence.
Managementofthisdiseasehasproventobeexpensiveandisgenerallyreservedforhighvalue(aestheticallydesirable)trees.Giventheapparentadaptationofthefungustowarmertemperaturesandrelativelydryconditions,andthelimitationsofcontroltacticsavailable,thereisahighprobabilityofsignificantoaklossinpreviouslyunaffectedareasalongtheGulfofMexicoandinGeorgiawithin50years.However,iftheapparentadaptationtowarmeranddrierconditionsprovesinadequateforcontinueddiseasespread,wewouldexpectanoverallslightlesseningoftheimpactofoakwiltintheSouth.
Sudden oak death—FirstreportedinCaliforniain1995,suddenoakdeath(SOD)isnowawell-establishedpestwithafairlylimitedrangeinCaliforniaandOregon.However,despitethisrelativelylimitedcurrentrange,itisbelievedthatifintroducedintotheeasternoakforesttheconsequencescouldbedire.
Literaturerelatingtothisdiseaseisextensive,buthasrecentlybeenreviewed(Kliejunas2010)andmuchofwhat
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followshasbeenextractedfromorcrosscheckedwiththatreviewtolimitthenumberofcitationsincludedhere.Thispublication,whichincludesa58pagebibliographyofrelevantliterature,isavailableontheinternetathttp://www.fs.fed.us/psw/publications/documents/psw_gtr234/.
SuddenoakdeathiscausedbyPhytophthoraramorum,afungus,whichcausesseveralnonspecificsymptomsdependingonthehostandhostpartaffected.Symptomsincludestemorbolecankers,twigblight(dieback),andleafblight.Individualplantspeciescandisplaymorethanoneoronlyonesymptomtype(seehttp://rapra.csl.gov.uk/background/hosts.cfmforlinkstoimagesofsymptomsonavarietyofhosts).
Cankersappearinthephloem(tissuesthatcarrysugarsawayfromtheleavesofatree)whichmaybediscoloredabrightred,andspreaduntiltheyreachthexylem(tissuesthatcarrywaterandmineralsupfromtheroot;woodfiber).Cankersaresunken,“bleed”sap,andaregenerallyrestrictedtothelowerportionofthetreetrunk.Theamountofbleedingisvariableevenonasingletreeandmayberelatedtoenvironmentallyavailablewaterandtheageofthecanker.Declinesymptoms(lossofleaves)andcrowndeathfirstappearatthetopofthetreeandspreadrapidlydownthroughthecrownoftenresultingintreedeath(Garbelottoandothers2001).
Thelistofhostscurrentlyreportedforthispestisextensive.Asof2010thelistincludes45provenregulatedhostsplusanother82associatedhostsregulatedinthenurserytrade(USDAAnimalandPlantHealthInspectionService2010a).HostswithstemorbranchcankeringincludeCaliforniatanoak(Lithocarpusdensiflora),coastliveoak(Quercusagrifolia),Californiablackoak(Quercuskelloggii),andShreve’soak(Quercusparvulavar.shrevei).Inaddition,fieldandgreenhouseinoculationexperiments(Rizzoandothers2002)confirmthatthefunguscancauseavarietyofleafandbranchsymptoms,butgenerallynotstemcankering,onrhododendronandazalea(Rhododendronspp.),madrone(Arbutusmenziesii),huckleberry(Vaciniumovatum),manzanita(Arctostaphylossp.),Californiabaylaurel(Umbellulariacalifornica),buckeye(Aesculuscalifornica),bigleafmaple(Acermacrophyllum),toyon(Heteromelesarbutifolia),Californiacoffeeberry(Rhamnuscalifornica),honeysuckle(Lonicerahispidula),andalonglistofotherplants.
Althoughfewofthesespeciesoccurineasternforests,severalofthemcanbefoundinsignificantnumbers.EarlyresultsbyRizzoandothers(2002)showthatnorthernredoakandpinoak(Q.palustirs)aresusceptibletoinfection.InCaliforniagreenhousetests,seedlingsofbotheasternoakspeciesdevelopedlesionsalmosttwiceaslongasthoseformedontheoakseedlingsfromPacificcoastalareasandroughlyequaltothoseformedontanoak(consideredthemostsusceptiblespeciesinCalifornia).Theseresultssuggest
that,allconditionsbeingequal,thesespeciesshouldbehighlysusceptibletosuddenoakdeath.
Kliejunas(2003)ratedtheriskposedbythisdiseaseasveryhigh,butcautionsthatthedegreeofuncertaintyrelatedtofuturediseaseriskisalsohighbasedonlackofknowledgeaboutthehostrange.Notingtheabsenceofcontrolmeasures,hisriskassessmentpredictsrapidspreadbywind,water,andhumantransportofinfectedplants;andsuggeststhepotentialforsevereeconomicandecologiclosses,reductionsinbiodiversity,andindirectimpactsonsensitiveorcriticalhabitatforat-riskplantandanimalcommunities.
Basedonpasthistorywithinvasivespecies,itiseasytoprojectthatitisnotamatterof“if,”but“when,”suddenoakdeathwillgainafootholdineasternoakforests(seealternativehypothesisbelowas“Note”).Ifthediseasereachessouthernforests,therolethatclimatewouldplayisfarfromcertain.Alsouncertain,lackingbasicepidemiologicalresearch,isthepotentialeffectsoneasternspecies;thesecouldrangefrominsignificanttopotentiallycatastrophic(rivalingtheeffectsofchestnutblight).
Suddenoakdeathappearstohavethepotentialtodevastatetheeasternoakpopulation,evenabsentclimatechangeconsiderations(Kliejunas2010,chapter4).Increasedtemperaturesandatmosphericcarbondioxidecouldbeexpectedtoincreasegrowthofboththepathogenanditshost,atleastintheshortterm.Thateffectwouldbesomewhatcounteractedbyreductionsinprecipitationandincreasedozoneinconjunctionwiththewarmertemperatures.Nevertheless,onceacclimatedtotheeasternforest,thediseasewouldprobablyspreadevenfasterthanithasinCalifornia.
Usingthedistributionofknownorlikelyhosts,climateconditionsadequateforthesurvivalandpropagationofthepathogen,andprobablepathwaysofintroductionofthediseaseoutsideofitscurrentrangeKochandSmith(2008a;fig.16.6)projectapotentialrangeforthisdisease.VerysimilarpotentialrangeisindicatedbyDEFRA,Fowlerandothers,andMargaryandothers.KellyandothersandVenetteandCohenproposesomewhatdifferentpotentialrangesbutbothincludesignificantSouthernforestareas(Kliejunas2010,chapter4).
Climate-inducedlossesofnativeoaksattheirsouthernmargins(Iversonandothers1999)wouldreducethepotentialincidenceofdisease,butonlyslightly,andwouldnotslowtheprogressofthediseaseinotherpartsofitspotentialrange.Sturrockandothers(2011)statethat,basedonCLIMEXprojections,changingclimatewilldecreasesubstantiallytheareaintheEasternUnitedStatesfavorableorveryfavorableforP.ramorum.
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counties(withsuspecttreesoccurringinsimilarsettingsinanadditional10counties);asyetnowoodlandorforestsurveyshavebeenconducted.AlthoughtheTennesseeinfectionswerethefirstreportedeastoftheGreatPlains,theymayhavebeenoccurringsincethe1990s.Thefullextentofthisinfectionisasyettobedetermined.
Symptomsofthediseaseincludeafoliagewiltinwhichtheleavesprogressrapidlyfromgreenthroughyellowandthentobrown.Wiltingprogressesfromthetopofthecrowndownwardasbranchesdie.IntheWest,thediebackandultimatedeathofinfectedtreestakesaboutthreeyears.Symptomsatfirst(andcertainlywhenobservedatadistance)resemblethosecausedbydrought.Closerinspectionofdeadbranchesrevealsmanybeetleentryholesthroughthebarkandmany(oftensmall)cankersjustunderthebark.Ascankersincreaseinnumberandeachgrowsbiggeruntiltheareasofdeadtissuecoalesceandgirdlethebranch.Inthelaterstagesofdiebackthebeetlesmayattacktheboleofthetreeacceleratingitsdeath(Seyboldandothers2010).
Controlmeasuresforthousandcankersdiseasehavebeenproposedbutnotyetevaluated.BecausethecurrentrangeofthefungalpestisgenerallyhotteranddrierthanTennessee’sclimate,thediseaseishighlyunlikelytoencountertemperaturebarriersthatwouldlimititsspreadintosouthernforests.Andpredictedawarmingclimateislikelytohavelittleeffect;thepathogenandvectororiginatedinahotdryareaoftheSouthwestbutbothhavemovedintothecooler,moisterclimateofcentralTennessee.Findingnobarrierstospread,thousandcankersdiseasecouldoccupytheentirerangeofblackwalnutwithin50years,similartotheprojectedspreadoflaurelwilt.
Additional concerns
Althoughwecanmakerelativelyuncertainpredictionsaboutthefutureofknownpests,predictingcurrentlyendemicorganismsthatmaybecomepestsororganismsfromotherlocationsthatmayinvadetheSouthisvirtuallyimpossible.Lovettandothers(2006)predictthatforestpestswillbetheprimarysourceofchangesineasternforestsbutcautionedagainstspeculationonspecificchangesorspecificpestintroductions.
Animportantconsiderationishumancausedchangeintheforestlandbasedrivenbyincreasingandshiftingpopulationsandeconomicconditions.Asshowninchapter5,alloftheCornerstoneFuturesforecastthattotalforestacreagewilldeclineoverthenext50years,onlyplantedpineisexpectedtoexpand,theoak-hickorytypeisexpectedtoremainrelativelystable,butthethreeotherforesttypesconsideredareexpectedtodecline.Additionally,totalforestbiomassisexpectedtoincreaseatfirstbutthendeclinesomewhat.
Ageneralizedimplicationofthesepotentialshiftsisrelativelystraightforward.Becausepestactivityappearstobebasicallyalinearresponsetoavailability,lessbiomasswouldindicateless(inabsoluteterms)lossofbiomasstopests.However,plantedsoftwoodswouldbeexpectedtoshowanincreaseinabsolutelossproportionaltotheincreaseinplantedacreage.
Thepossibleeffectsoffragmentation,parcelization,andurbanizationonpestimpactsandmanagementaresocomplex(andlargelyunknown)thatitisnotprudentorfeasibletoattempttoidentifyspecificinteractions.Generally,parcelization(greaternumberoflandownersonsmallerunitsofland)maycomplicatepestpreventionand/orsuppressionbymakingitmoredifficulttoattaineffectivemanagementonsignificantacreagesduetothegreaternumberoflandownersinvolved.Ontheotherhand,fragmentationandurbanizationwouldinterruptordecreasetheamountandcontinuityofhostspecies,therebypotentiallydecreasingthespreadandimpactsofpests.
Weexpectcontinuingintroduction(throughinternationalanddomesticcommerceandtourism)ofnonnativeinsectsanddiseaseswhichcouldbecomepestsofforesttrees,despiteimpositionofinspectionsandquarantines.Whichorganismsmightbeintroduced,andthenwhichofthesemightbecomepestspeciesisthesourceofsignificantspeculation,butisrelativelyunpredictable.
DiScuSSioN AND coNcluSioNS
Future considerations for Pest-host Relationships
Plannedadaptation(SpittlehouseandStewart2003)shouldreducevulnerabilityforcommercialtreespeciesatselectedsites.However,manyforestspecieswillhavetoadaptautonomouslyandsocietywillhavetoadjusttotheresult(Winnett1998).Forestpestdistributionchangescausedbyclimatechangearelikelycloselytiedtoshiftsinhostdistribution(Sturrock2007).
Someecosystemsareexpectedtobenew:newcommunitiesoftreeandplantspecieswithdifferentsuitesofinsectsandpathogens.Ifforestsdoremainonaparticularsite,similarfunctionaltypesofinsectsandpathogensarelikelytoremain,althoughtheymaybeincludedifferentspeciesthanatpresent(Beukemaandothers2007).Pathogensexpandingtheirrangesandcontacting‘new’hostsandvectorsmaymeanthatnewpathosystemsprobablywillemerge.Interactionsbetweenpathogensmaychange(Sturrock2007).
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Climatechangemayamplifytheimpactandaggressivenessofpathogensoralterthebalancebetweenpathogensandtheirnaturalenemies;itmayalsochangethestatusofweak/opportunisticpathogenssuchthattheyareabletoinfectanddamagestressedtreehosts(Sturrock2007).
Treedeclineislikelytoincreaseinawarmeranddrierclimate,regardlessofinputsfromdiseasesandinsects.Theeffectofwarmeranddrierclimateistostresstreesusedtoacoolerandmoisterregime.Thisstressaloneshouldcauseanincreaseintheincidenceofdecliningtrees,butcompoundedbythepresenceofopportunisticinsectsandpathogens,thereisastrongpossibilitythatthisincreaseindecliningtreescouldbesignificant.Increasingincidenceofdeclineshouldeventuallydiminishasnewadaptedecosystemsformintheregion,butthisisnotexpectedtooccurwithinthenext50years.
Almosteverystudyandreviewofclimatechangeeffectsonforestshasacommoncaveat—thecomplexityoftheecosystemsandpestsystems,aboutwhichrelativelylittleisknown(Sturrock2007).ThedifficultyinpredictingthefutureofplantdiseaseishighlightedbyWoodsandothers(2005),whoreportonanendemicneedleblightfungus(Mycosphaerellapini)thatpreviouslyhadonlyminimalimpactonnativeforesttreesinBritishColumbia.However,recently,inapparentresponsetoalocalincreaseinsummerprecipitation,thisdiseasehasbeencausingextensivemortalityoflodgepolepines.Whileadmittingthatestablishingcausalityoftheincreasedvirulenceofthisendemicpathogenisfraughtwithriskofmisinterpretationoftheevidence,theyindicatethelinktoprecipitation(whiledismissingwarmertemperatures)appearstobefargreaterthan“circumstantial.”Nopriorindicationofthisshifttovirulenceappearsintheliterature—theeventwasunprecedented,unpredicted,andpossiblyunpredictable.Inpartialconfirmation,Sturrock(2007)notesthatwetterspringsinsomeregionsmayresultinincreasedfoliagediseaseswithoutventuringtopredictsubsequentpossiblehost/pestscenarios.
Endemicrootrotfungi(Inonotusschweinitzeii,I.tomentosus,orGanodermaspp.),whichcurrentlycauselimiteddamage,orinsectssuchasengraverbeetlesorspeciesofwoodborerscouldbecomeimportantmanagementconcernsorcouldfadeintoobscurityfromamanagementstandpoint.Thefungithatcauselittleleafdisease,suddenoakdeath(BrasierandScott1994),andotherinfectionsarepredictedtoincreasetheiractivityintemperatezonesintheNorthernandSouthernHemispheresastheymigrateawayfromthetropics.UnderchangingclimaticconditionsthesefungiareexpectedtocausemoredamagetoexistingurbanandforesttreehostsintheSouthandtoexpandthenumberofspeciestheycaninfect.Expectedtobeespeciallyprevalentanddamaging
arethose,likethelittleleafdiseasefungus,thatcangrowintemperatureshigherthan28oC(Broadmeadow2005).
Increaseddroughtstressonhostsmaymeanincreasedmortalityfromrootpathogens.PathogenicArmillariaspp.fungimaybeassistedbytheimpairmentofhosttolerancecausedbyclimatechange-inducedstress:thismayenablelesspathogenicfungitobecomemoresuccessfulonstressedtrees(Sturrock2007).Incidenceofoakandbeechdecline,highlycomplexdisorders,islikelytoincreaseifthepredictedfrequencyandseverityofsummerdroughtstressproveaccurate(Broadmeadow2005).
Achangingclimatewithincreasedtemperatures,increasedevapotranspiration,andextremeweathereventswouldincreasethefrequencyandseverityofstressfactors,whichmayleadtomorefrequentforestdeclines(Sturrock2007).Pathogenevolutioncouldbeacceleratedbymutationresultingfromincreasedsunlightorincreasedreproductionrates(shorterlifecyclesunderhighertemperatures)thatcouldleadtohostresistancebeingovercomemorerapidly(CoakleyandScherm1996).
Basedontheseoccurrencesandtrends,thefollowingbasicpatternshaveemergedonwhichwehavebuiltourprojectionsoffutureimpactsofpests:
•Thecurrentemphasisonlongleafpinerestoration,coupledwithincreasingtemperatureanddecreasingrainfallshouldresultinameasurableshiftinthepopulationdistributionofsouthernyellowpinetypes,bothspatiallyandnumerically.
•BorealforestspeciesareexpectedtohavereducedrangesintheSouthduetothecombinedeffectsofincreasedtemperatureanddecreasedavailablewater.
• Pestsassociatedwithsouthernhostspeciesareexpectedtomigratewiththeirhostswithfewexceptions.TheexceptionsarethosepeststhatalreadyoccurthroughouttheSouthandextendintothenorthernpartoftheUnitedStates.
•Althoughlong-termprojectionssuggestthatcoastalsavannahwillreplaceforestsinmanycoastalandcoastal-plainlocations,theprogressofthischangewithinthenext50yearsisnotexpectedtobesevere.
•Mostrootrottingdiseasesareexpectedtorespondaggressivelytothecombinationofwarmersoiltemperatureandreducedprecipitation.Thiscombinationofheatanddroughtisexpectedtoresultinanincreaseindiebackanddeclineamongmanytreespecies,oftenprovidingfurtherstressthatcouldactasaprecursortosuccessfulinvasion/colonizationbyrootrottingfungi.Newlystressedtreesalsomaybecomethefocusofinsectattack.
•Treessufferinglong-termstressmayprovetobemoreresistanttosecondarypestattackbecauseoflowerphysiologicalactivityandreducedavailabilityofresourcesneededbypestorganisms.
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•Treediseaseswhichaffectprimarilystemandbranchtissuearesubjectdirectlytothepotentialeffectsofwarmertemperaturesandadrierenvironment.Atfirst,warmertemperaturesandincreasedcarbondioxideintheatmosphereareexpectedtohaveastimulatoryeffectonbothhostandpathogen.However,theanticipatedloweravailabilityofwatershouldgenerallyfunctionmoreagainstthehostplantthanthefungiinfectingit,favoringanincreaseindisease.Thisassumesthatthetemperatureincreasedoesnotexceedthethermaldeathpointofthefungusoritsspores.
• Foliageattackingfungiaresubjecttosignificantpressurefromlightandthemicroclimateinthehost’sleaves.Althoughsignificantlossofsporeviabilityiscommonontheuppersurfaceofleaves,anychangeintheamountofsunlightwillnormallyalterthesurvivalrate;moresunlightresultsinlowersporesurvivalandlesssuccessfulinfectionandviceversa.Themicroclimateoftheundersideofleavesisalsocriticaltothesuccessoffoliarpathogens.Loweratmosphericmoistureresultingfromlessrainfall,fog,anddew(withasecondaryeffectofreducedsecretionofliquids)isexpectedtoreducetheeffectivenessofcolonizationbyleaf-infectingfungi.
• Longerandwarmersummertimetemperaturesareexpectedtoincreasepathogenandinsectactivity.Insectpopulationsmayshowsimpleincreasesinnumberduetotheavailabilityofadditionalhostmaterialonwhichtobrowse,ormaybeabletoproduceanadditionalgenerationeachyear.
managing Pests under changing conditions
Manyland-managementdecisionsmadetodayarebasedontheassumptionthattheclimatewillremainrelativelystablethroughoutaforest’slife—anassumptionthatmayhaveworkedwellinthepastbutisbeingchallengedbyclimatechange.Evenwithoutaclearviewofthefutureclimateandforest,itispossibletodevelopadaptivestrategiesnow.Adaptationinforestmanagementrequiresaplannedresponsewellinadvanceoftheimpactsofclimatechange(SpittlehouseandStewart2003).Thisisespeciallyimportantwhentherotationperiodsarelong(LemmenandWarren2004).
Changesinclimate,especiallyiftheyleadtogreatervariabilityamongandwithinregions,tendtoaddextrauncertaintytodecisionmaking(Garrettandothers2006).Burtonandothers(2002)appeartocontesttheconclusionofSpittlehouseandStewart(2003)citedabovewiththeirconclusionthatdevelopmentofadaptationmeasuresforsometimeinthefuture,underanuncertainclimate,inanunknownsocioeconomiccontextisboundtobehighlyspeculative.Notso;reconcilingtheapparentcontradictionhereisthenecessitythatbestprofessionaljudgmentratherthanprovensciencebebroughttobearonplanningforanuncertain,butgenerallypredictedfuture.
Adaptivestrategiesincluderesilienceoptionsandresponseoptions.Mitigationoptionsincludeoptionstosequestercarbonandreduceoverallgreenhousegasemissions(Millarandothers2007).Copingstrategiesforonedisturbancetypeareoftenappropriatemanagementresponsestootherdisturbancetypes.Beforedisturbanceoccursforestscanbemanagedtoreducevulnerabilityortoenhancerecovery.Treescanbeplantedthatarelesssusceptibletodisturbance.Speciesthatpromotedisturbancecanberemoved(Daleandothers2001).Millarandothers(2007)proposethefollowinggeneralizedstrategies:
• Improve resistance in hosts: Fromhigh-valueplantationsneartoharvesttohigh-priorityendangeredspecieswithlimitedavailablehabitat,maintainingthestatusquoforashorttimemaybetheonlyorthebestoption.Resistancepracticesseektoimproveforestdefensesagainstdirectandindirecteffectsofrapidenvironmentalchangesbyreducingtheundesirableorextremeeffectsoffires,insects,anddiseases.Becausetheymayrequireintensiveintervention,theseoptionsarebestappliedonlyintheshort-term.
•Promote resilience to change: Resilientforestsarethosethatnotonlyaccommodategradualchangesrelatedtoclimatebutalsotendtoreturntowardapriorconditionafterdisturbance,eithernaturallyorwithmanagementassistance.Promotingresilienceisthemostcommonlysuggestedadaptiveoptiondiscussedinaclimatechangecontext.Thisprocessmayalsobecomeintensiveaschangesinclimateaccumulateovertime.
•Enable forests to respond to change: Theseadaptationoptionsintentionallyaccommodatechangeratherthanresistit.Treatmentsimplementedwouldmimic,assist,orenableongoingnaturaladaptiveprocessessuchasspeciesdispersalandmigration,populationmortalityandcolonization,communitycompositionanddominancewithincommunities,anddisturbanceregimes.Somepotentialpracticesinclude:(1)Increaseredundancyandbuffers,manageforasynchrony,realignsignificantlydisruptedconditions,anduseestablishmentphasetoresetsuccession;(2)Establish“neo-native”forests,experimentwithrefugia,andpromoteconnectedlandscapes;(3)Developindicatorsasaprerequisiteforanykindofdecisionmakingandsurveillancenetworkstoassessspatialandtemporalevolutionofdiseasesandimproveepidemiologicalmodels;(4)Takeananticipatoryandpreventiveapproachbasedonriskanalysiswhenaddressingdiseasemanagementinforestecosystems(evenmoresothanforcrops),avoidtotalrelianceononeortwocontrolstrategies(asHain[2006]recommendedwhendiscussingtheunsatisfactoryresultsofbalsamwoollyadelgidcontrolefforts),andanticipatesurprisesandthresholdeffects.
•Diseasemanagementoptionscouldbealtered(Coakleyandothers1999)orimposed.Forexample,althoughitisknownthatmovementoffirewood,nurserystock,andevenfamilytrailersandboatsisresponsibleforthetransportofmany
485chAPTeR 16. Invasive Pests—Insects and Diseases
species,thereisnocohesivestrategyforaddressingthisproblem(Moserandothers2009).Otheractionsproposedformanaginginsectsanddiseasesinclude:
•Avoiddisseminationofpestsintoclimaticallyfavorablezoneswheretheycouldfindnaïvehostpopulationsbypracticingstricthygienemeasures,basedonthemostprobabledisseminationpathwaysoforganisms(inseeds,wood,andplants).
•Reducevulnerabilitytofuturedisturbancebymanagingtreedensity,speciescomposition,foreststructure,andlocationandtimingofactivities(Daleandothers2001).
• Increaselight,water,andnutrientavailabilitytotheuninfected/uninfestedtreesanddecreasesusceptibilitytopestattackbypracticingprecommercialthinning,sanitationremoval,orselectiveremovalofsuppressed,damaged,orpoorqualityindividuals(Gottshalk1995,Papadopol2000,WargoandHarrington1991).
•Underplantwithotherspeciesorgenotypesinforestswherethecurrentcompositionisunacceptableasasourceofregeneration(SpittlehouseandStewart2003).
• Shortenrotationstoreducetheperiodofstandvulnerabilitytoinsectordiseaseattack,andreplanttospeedtheestablishmentofbetter-adaptedforesttypes(Gottshalk1995;Parkerandothers2000).
•Usepesticidesinsituationswheresilviculturalorothermeansofpestmanagementareineffective(Parkerandothers2000);however,becausemorphologicalorphysiologicalchangesinthehostresultingfromincreasedcarbondioxideuptakecouldaffectuptake,translocation,andmetabolismofsystemicfungicides(Coakleyandothers1999),incorporateintegratedpestmanagementpractices.
•Expandandimproveexistingmonitoringeffortstoincludeanexpectedincreaseinthenumberofnew,introducedplantdiseases(Sturrock2007).
•Assistinthemigrationofforests,byintroducingcarefullyselectedtreespecies(includingusingbiotechnologytechniquesinsomesituations)inregionsbeyondtheircurrentranges,beingmindfulofthepotentialforunforeseenconsequences.
Withrespecttononnativeinvasivespeciesmanagement,Moserandothers(2009)recommendfivepriorities:(1)promotingeducationandawareness,(2)expandingearlydetectionandactivemanagementandintensifyingenforcementofquarantines,(3)buildingthecapacitytoincreaseunderstandingofandtreatmentsforNNIScontrol,(4)strengtheningthebasicforesthealthcurriculum,and,(5)encouragingcrossagencycollaborationandinvestment.
Althoughtheprocessofplanningandactingtoprepareforafuturemostprobablyaffectedbyclimatechangeisfraught
withuncertainty,notplanningandactingwilllikelyresultingreatereconomicandsocialdisruption.Successcanonlybeachievedifthoseinenvironmentallysensitivemanagementrolesarewellinformedandexercisetheirbestjudgment.
Thesingleconsistentthemethroughouttheliteratureonpestimpactsandclimatechangeisthatminimizingecologicalchange(anddisruption)requiresmaximumpossiblebiodiversity,eitherthroughasystemofprotectedrefugiaorbydirectadaptivemanagementforspecificcharacteristics.
Differingperceptionsofriskandadaptationmayleadtoincreasedtensionamongvariousgroups.Conflictingprioritiesandmandatescouldalsoleadtofutureproblems(LemmenandWarren2004).Inthesesituations,caremustbetakentoadoptadecisionmakingprocessthatidentifiesandevaluatesallissuesandemploysthebestecologicalscience.
kNoWleDGe AND iNFoRmATioN GAPS
Asshouldbeclearfromtheabovediscussionofcurrentknowledgeandfromourprojectionsofthefutureactivityofknownpests,hugeuncertaintydominatesthesubjectofpestmanagementandclimatechange,withsignificantgapsexistinginbaselineknowledgemakinganygeneralizedquantitativemodelingoffutureconditionsimpossible.Althoughsomespecificpestbehaviorshavebeenprojected,mostofthemarequalitative.Lackinggeneralizedandoftenspecificbaselinedataleavesmodeling(quantitativeprojection)adesiredtoolwhosetimehasyettocome.Currentlyunavailabledatathatwouldcontributetoageneralizedprojectionofpotentialfuturepestactivityinforests(Beukemaandothers2007;ChakrabortyandDatta2003;Hain2006;LemmenandWarren2004;Loganandothers2003;MamlstromandRaffa2000;Rogersandothers1994;Scherm2004;and,Seem2004)include:
Informationonhostbiologyandresponsetopests:theroleofchangingsecondarymetabolites(primarilyphenolsorphenol-like)underchangingenvironmentalconditions;thefunctionalcomponentsofrespiration(construction,maintenance,andionuptake)aswellascarboncostsduetorootexudation;theroleofwaterintreehealth;thegenotypicvariabilityandplasticityofhosts;waterbalancethresholdasitaffectsdirectmortalityofhostplants,theeffectsofclimatechangeonhostdefensivemechanisms(physiological,morphological,orother);theimpactofclimatechangeonbiodiversityandtheroleofbiodiversityinecosystemfunctionsandpestmanagement/prevention;and,projections
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ofhostmigrationandavailabilityundertheinfluenceofclimatechange.
Informationonforestpests:currentdistributionsandrangesofpests;influenceofmycorrhizaeonplanthealthunderclimatechange;directandindirecteffectsofcarbondioxide,ozone,andUV-Bonrootsandroot-surfacemicroflorasundernaturalconditions;knowledgeofinsectsandpathogensfromoutsidetheareasuchasMexicanbarkbeetlesandvariousAsianinsects;mechanismsbywhichchangesincarbondioxideandprecipitationalterpestsurvival,growth,susceptibilityandinteractions
Informationtoaddclarityandspecificityonpest/hostinteractions:dispersalstructureanddistanceandinterconnectednessoftemperature,phenologyandpestpopulationgrowthrate;phenologicalrelationshipsamongtreesandpests;roleofclimateoninsectsandpathogensinrelationtoavailablewater;baselinedataonpestsofnaturalpopulationsthatidentifytheseparateofmultipleclimatevariablesandproblemstheycause(includingforecastsofepiphytoticsorepizootics,andevaluationstheroleofevolution);pest/predatorinteractionsandresponses,relationshipsamongclimate,pests,andtheirparasites;minimumandmaximumtemperaturepreferencesofpestsandpest/hostinteractionsandresponsetotemperatureextremes;protocolforidentifyingthe“drivers”thattransformnewinsectsanddiseasesintopests;disturbanceregimesandtheirinteractiveimpacts;and,synergiesamongfire,insects,andpathogens.
Modelsandmodelingprotocolsneeded:modelsthatincorporatelocalmeteorologicaldata;improvedspatially-explicitclimatepredictionsatfinerscales(averagedailypatternsandprojectedvariationsfromtheaverage);effectsofdown-scalingorup-scalingdatafromvariousmodelsandappropriatelinkingtoolsforincreasingtheaccuracyofthesepredictiveprocessestobemoreaccuratepredictors;functionalgroupratherthansingle-speciesmodels;and,predictivemodelsthatincorporatedataondisturbancesanddisturbanceimpacts.
Managementinformationneeded:anewprotocolforaddressingtheresearchneedsofinvasiveforestpeststhatinvolvesallstakeholdersinacoordinatedpartnership;andmanagementactionplansdevelopedinthefaceofno-analogvegetationsystemsandclimatechange.
AckNoWleDGmeNTS
OurappreciationisextendedtoChristopherAsaro,VirginiaDepartmentofForestry;MatthewP.Ayres,BiologicalSciencesDepartment,DartmouthCollege;FredP.Hain,DepartmentofEntomologyandFrankKoch,DepartmentofForestryandEnvironmentalResources,NorthCarolina
StateUniversity;EdwardL.Barnard,FloridaDivisionofForestry;RonaldF.BillingsandDonaldM.Grosman,TexasForestService;ScottCameronandJamesJohnson,GeorgiaForestryCommission;StephenR.Clarke,JohnA.Ghent,WilliamE.Jones,BruceD.Moltzan,DerekPuckett,JamesD.Smith,DaleA.Starkey,andBorysM.Tkacz,ForestHealthProtection,SusanJ.Frankel,PacificSouthwestResearchStation,andKierKlepzig,AlbertE.‘Bud’Mayfield,III,DanielMiller,WilliamJ.Otrosina,andA.DanielWilson,SouthernResearchStation,U.S.DepartmentofAgriculture,ForestService.
liTeRATuRe ciTeD
Anagnostakis,S.L.1978.TheAmericanchestnut:newhopeforafallen giant.Bull.777.NewHaven,CT:ConnecticutAgriculturalExperimentStation.9p.
Anderson,R.L.;Powers,H.;Snow,G.1980.Howtoidentifyfusiformrustandwhattodoaboutit.For.Bull.SA–FB/P24.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestInsectandDiseaseManagement.12p.
Andreadis,T.G.;Weseloh,R.M.1990.DiscoveryofEntomophagamaimaigainNorthAmericangypsymoth,Lymantriadispar.ProceedingsoftheNationalAcademyofScience(U.S.).87:2461–2465.
Antipin,J.;Dilley,D.2004.Chicagovs.theAsianlonghornedbeetle:aportraitofsuccess.Misc.Publ.MP-1593.Washington,DC:U.S.DepartmentofAgricultureForestService.51p.
Applegate,H.W.1971.Annosusrootrotmortalityinonce-thinnedloblollypineplantationsinTennessee.PlantDiseaseReporter.55:625–627.
Asaro,C.;Fettig,C.J.;McCravy,K.W.[andothers].2003.TheNantucketpinetipmoth:aliteraturereviewwithmanagementimplications.JournalofEntomologicalScience.38:1–40.
Balch,R.E.1927.DyingoaksintheSouthernAppalachians.ForestWorker.3(7):13.
Batzer,H.O.;Morris,R.C.1978.Foresttentcaterpillar.ForestInsectandDiseaseLeaflet9.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Beal,J.A.1926.Frostkillsoak.JournalofForestry.24:949–950.
Bentz,S.E.;Riedel,L.G.H.;Pooler,M.R.;Townsend,A.M.2002.Hybridizationandself-compatibilityincontrolledpollinationsofeasternNorthAmericanandAsianhemlock(Tsuga)species.JournalofArboriculture.28:200-205.
Berisford,C.W.1988.TheNantucketpinetipmoth.In:Berryman,A.A.,ed.Dynamicsofforestinsectpopulations:patterns,causes,andimplications.NewYork:PlenumPublishingCorp.:141–161.
Beukema,S.J.;Robinson,D.C.E.;Greig,L.A.2007.Forests,insectsandpathogensandclimatechange:workshopreport.Prineville,OR:TheWesternWildlandsEnvironmentalThreatAssessmentCenter.20p.http://www.fs.fed.us/wwetac/workshops/Forest%20Pests%20and%20Climate%20Report.pdf.[Dateaccessed:November22,2010].
Billings,R.F.1980.Directcontrol.In:Thatcher,R.C.;Searcy,J.L.;Coster,J.E.;HertelG.D.,eds.Thesouthernpinebeetle.Tech.Bull.1631.Washington,DC:U.S.DepartmentofAgricultureForestService,ExpandedSouthernPineBeetleResearchandApplicationsProgram:178-192.
Billings,R.F.;Kibbe,C.A.1978.SeasonalchangesbetweensouthernpinebeetlebrooddevelopmentandloblollypinefoliagecolorineasternTexas.SouthwesternEntomologist.3:89–95.
487chAPTeR 16. Invasive Pests—Insects and Diseases
Billings,R.F.;Upton,W.W.2010.Amethodologyforassessingannualriskofsouthernpinebeetleoutbreaksacrossthesouthernregionusingpheromonetraps.In:Pye,J.M.;Rauscher,H.M.;Sands,Y.;[andothers],tech.eds.Advancesinthreatassessmentandtheirapplicationtoforestandrangelandmanagement.Gen.Tech.Rep.PNW-GTR-802.Portland,OR:U.S.DepartmentofAgricultureForestService,PacificNorthwestandSouthernResearchStations:73-85.Vol.1.
Boyce,J.S.1961.Chestnutblight.In:Forestpathology.3rded.NewYork:McGraw-HillBookCo.:285–292.
Brasier,C.M.1991.Ophiostomanovo-ulmisp.nov.,causativeagentofcurrentDutchelmdiseasepandemics.Mycopathologia.115:151-161.
Brasier,C.M.;Scott,J.K.1994.Europeanoakdeclinesandglobalwarming:atheoreticalassessmentwithspecialreferencetotheactivityofPhytophthoracinnamomi.BulletinOEPP.24(1):221–232.
Broadmeadow,M.;Ray,D.2005.ClimatechangeandBritishwoodland.Inf.Note69.Edinburgh,UnitedKingdom:ForestryCommission.www.forestresearch.gov.uk/pdf/fcin069.pdf/$FILE/fcin069.pdf.[Dateaccessed:November22,2010].
Brown,H.D.;McDowell,W.E.1968.Statusofloblollypinedie-offontheOakmulgeeDistrict,TalladegaNationalForest,Alabama-1968.Rep.69–2–28.Pineville,LA:U.S.DepartmentofAgricultureForestService,ForestInsectandDiseaseManagement.22p.
Brown,H.D.;Peacher,P.H.;Wallace,H.W.1969.Statusofloblollypinedie-offontheOakmulgeeDistrict,TalladegaNationalForest,Alabama-1968.Rep.70–2–3.Pineville,LA:U.S.DepartmentofAgricultureForestService,ForestInsectandDiseaseManagement.7p.
Burton,I.;Huq,S.;Lim,B.[andothers].2002.Fromimpactsassessmenttoadaptationpriorities:theshapingofadaptationpolicy.ClimatePolicy.2:145–159.
Cameron,R.S.;Billings,R.F.1988.Southernpinebeetle:factorsassociatedwithspotoccurrenceandspreadinyoungplantations.SouthernJournalofAppliedForestry.12:208-214.
Campbell,R.W.;Sloan,R.J.1977.Foreststandresponsestodefoliationbygypsymoth.ForestScienceMonograph19.ForestScience.23(Suppl.):1–35.
Campbell,W.A.;Copeland,O.L.,Jr.1954.Littleleafdiseaseofshortleafandloblollypines.Circ.940.Washington,DC:U.S.DepartmentofAgriculture.41p.
Chakraborty,S.;Datta,S.2003.HowwillplantpathogensadapttohostplantresistanceatelevatedCO2underachangingclimate?NewPhytologist.159:733–742.
Chakraborty,S.;Murray,G.M.;Magarey,P.A.[andothers].1998.PotentialimpactofclimatechangeonplantdiseasesofeconomicsignificancetoAustralia.AustralasianPlantPathology.27:15–35.
Cherret,J.M.1986.Historyoftheleaf-cuttingantproblem.In:Lofgren,C.S.;VanderMeer,R.K.,eds.Fireantsandleaf-cutting-antsbiologyandmanagement.Boulder,CO:WestviewPress:10–17.
Coakley,S.M.;Scherm,H.1996.Plantdiseaseinachangingglobalenvironment.AspectsofAppliedBiology.45:227–238.
Coakley,S.M.;Scherm,H.;Chakraborty,S.1999.Climatechangeandplantdiseasemanagement.AnnualReviewofPhytopathology.37:399–426.
Conner,M.D.;Wilkinson,R.C.1983.IpsbarkbeetlesintheSouth.ForestInsectandDiseaseLeaflet129.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Cordell,C.E.;Anderson,R.L.;Kais,A.G.1989.Howtoidentifyandcontrolbrown-spotdiseaseonlongleafpine.Atlanta,GA:U.S.DepartmentofAgricultureForestService,SouthernRegion.10p.
Coulson,R.N.;Flamm,R.O.;Pulley,P.E.[andothers].1986.Responseofthesouthernpinebarkbeetleguildtohostdisturbance.EnvironmentalEntomology.15:859–868.
Cowles,R.S.;Montgomery,M.E.;Cheah,C.A.S.J.2006.Activityandresiduesofimidaclopridappliedtosoilandtreetrunkstocontrolhemlockwoollyadelgid(Hemiptera:Adelgidae)inforests.JournalofEconomicEntomology.99:1258–1267.
Czabator,F.J.1971.Fusiformrustofsouthernpines—acriticalreview.Res.Pap.SO–65.NewOrleans:U.S.DepartmentofAgricultureForestService,SouthernForestExperimentStation.39p.
Dale,V.H.;Joyce,L.A.;McNulty,S.[andothers].2001.Climatechangeandforestdisturbances.BioScience.51:723–734.http://www.usgcrp.gov/usgcrp/Library/nationalassessment/forests/bioone2.pdf.[Dateaccessed:November22,2010].
D’Arcy,C.J.2005.Dutchelmdisease.SaintPaul,MN:AmericanPhytopathologicalSociety.http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/DutchElm.aspx.[Dateaccessed:November29,2012].
Dilling,C.;Lambdin,P.;Grant,J.[andothers].2010.SpatialandtemporaldistributionofimidaclopridineasternhemlockintheSouthernAppalachians.JournalofEconomicEntomology.103:368–373.
Doggett,C.A.;Grady,C.R.;Green,H.J.[andothers].1977.SeedlingdebarkingweevilsinNorthCarolina.For.Note31.Raleigh,NC:NorthCarolinaForestService,DepartmentofNaturalandEconomicResources.15p.
Drooz,A.T.1985.Foresttentcaterpillar.In:Insectsofeasternforests.Misc.Publ.1426.Washington,DC:U.S.DepartmentofAgricultureForestService:204-205.
Dull,C.W.;Ward,J.D.;Brown,H.D.[andothers].1988.EvaluationofspruceandfirmortalityintheSouthernAppalachianMountains.Rep.R8–PR13.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestPestManagement.92p.
Dwyer,J.P.;Cutter,B.E.;Wetteroff,J.J.1995.AdendrochronologicalstudyofblackandscarletoakdeclineintheMissouriOzarks.ForestEcologyandManagement.75:69–75.
Eckhardt,L.G.;Goyer,R.A.;Klepzig,K.D.[andothers].2004a.InteractionofHylastesspecies(Gleeptera:Scolytidae)withLeptographiumassociatedwithloblollypinedecline.JournalofEconomicEntomology.97:468–474.
Echhardt,L.G.;Jones,J.P.;Klepzig,K.D.2004b.PathogenicityofLeptographiumspeciesassociatedwithloblollypinedecline.PlantDisease.88:1174-1178.
EmeraldAshBorerInformationNetwork.2010.Emeraldashborerinformationnetwork.Lansing,MI:MichiganStateUniversity.http://www.emeraldashborer.info/index.cfm.[Dateaccessed:June10,2011].
Fitzgerald,T.D.1995.Thetentcaterpillars.CornellSeriesinArthropodBiology.Ithaca,NY:CornellUniversityPress.303p.
Fraedrich,S.W.;Harrington,T.C.;Rabaglia,R.J.[andothers].2008.AfungalsymbiontoftheredbayambrosiabeetlecausesalethalwiltinredbayandotherLauraceaeintheSoutheasternUnitedStates.PlantDisease.92:215–224.
French,D.W.;Ascerno,M.E.;Stienstra,W.C.1980.TheDutchelmdisease.PublAg-BU-0518.St.Paul,MN:MinnesotaExtensionService,UniversityofMinnesota.10p.
Friedenberg,N.A.;Sarkar,S.;Kouchoukos,N.[andothers].2008.Temperatureextremes,densitydependence,andsouthernpinebeetle(Coleoptera:Curculionidae)populationdynamicsineastTexas.EnvironmentalEntomology.37:650–659.
488The Southern Forest Futures Project
Froelich,R.C.;Cowling,E.B.;Collicott,L.C.[andothers].1977.Fomesannosusreducesheightanddiametergrowthofplantedslashpine.ForestScience.23:299–306.
Gan,J.2004.Riskanddamageofsouthernpinebeetleoutbreaksunderglobalclimatechange.ForestEcologyandManagement.191:61–71.
Garbelotto,M.;Svihra,P.;Rizzo,D.2001.Suddenoakdeathsyndromefells3oakspecies.CaliforniaAgriculture.55(1):9–19.
Garrett,K.A.;Dendy,S.P.;Frank,E.E.[andothers].2006.Climatechangeeffectsonplantdisease:genomestoecosystems.AnnualReviewofPhytopathology.44:489–509.
Gottschalk,K.W.1995.Usingsilviculturetoimprovehealthinnortheasternconiferandeasternhardwoodforests.In:Eskew,L.G.,ed.Foresthealththroughsilviculture.Gen.TechRep.RM–267.FortCollins,CO:U.S.DepartmentofAgricultureForestService,RockyMountainExperimentStation:219–226.http://www.fs.fed.us/rm/pubs_rm/rm_gtr267/rm_gtr267_219_226.pdf.[Dateaccessed:November22,2010].
Grassano,S.;Costa,S.2008.Optimizingfungalproductionforhemlockwoollyadelgidsuppression[Abstract].In:Onken,B.;Reardon,R.FourthsymposiumonhemlockwoollyadelgidintheEasternUnitedStates.Publ.FHTET–2008–01.Morgantown,WV:U.S.DepartmentofAgricultureForestService,ForestHealthTechnologyEnterpriseTeam:111.http://na.fs.fed.us/fhp/hwa/pubs/proceedings/2008_proceedings/fhtet_2008.pdf.[Dateaccessed:November22,2010].
Gysel,L.W.1957.Acornproductionongood,medium,andpoorsitesinsouthernMichigan.JournalofForestry.55:570–574.
Hain,F.2006.Newthreatstoforesthealthrequirequickcomprehensiveresearchresponse.JournalofForestry.104(4):182–186.
Hajek,A.E.;Humber,R.A.;Elkinton,J.S.[andothers].1990.AllozymeandRFLPanalysesconfirmEntomophagamaimaigaresponsiblefor1989epizooticsinNorthAmericangypsymothpopulations.ProceedingsoftheNationalAcademyofScience(U.S.A.).87:6979–6982.
Hanula,J.L.;Mayfield,A.E.,III;Fraedrich,S.W.[andothers].2008.Biologyandhostassociationsofredbayambrosiabeetle(Coleoptera:Curculionidae:Scolytinae),exoticvectoroflaurelwiltkillingredbaytreesintheSoutheasternUnitedStates.JournalofEconomicEntomology.101:1276–1286.
Harrington,T.C.;Fraedrich,S.W.;Aghayeva,D.N.2008.Raffaellalauricola,anewambrosiabeetlesymbiontandpathogenontheLauraceae.Mycotaxon.104:399–404.
Haugen,D.A.;Hoebbeke,E.R.2005.Sirexwoodwasp–SirexnoctilioF.(Hymenoptera:Siricidae).Pestalert.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,StateandPrivateForestry,NortheasternArea.3p.
Haugen,L.2007.HowtoidentifyandmanageDutchelmdisease.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,StateandPrivateForestry,NortheasternArea.16p.http://na.fs.fed.us/pubs/detail.cfm?id=918.[Dateaccessed:November22,2010].
Haugen,L.;Stennes,M.1999.FungicideinjectiontocontrolDutchelmdisease:understandingtheoptions.PlantDiagnosticiansQuarterly.20(2):29-38.
Hepting,G.H.1974.DeathoftheAmericanchestnut.JournalofForestHistory.18:60–67.
Herms,D.A.;McCullough,D.G.;Smitley,D.R.[andothers].2009.Insecticideoptionsforprotectingashtreesfromemeraldashborer.NorthCentralIPMCenterBull.(unnumbered).Lansing,MI:NorthCentralIPMCenter.12p.http://www.emeraldashborer.info/files/Multistate_EAB_Insecticide_Fact_Sheet.pdf.[Dateaccessed:November22,2010].
Hess,N.J.;Eckhardt,L.G.;Menard,R.D.[andothers].2005.AssessmentofloblollypinedeclineontheOakmulgeeRangerDistrict,TalledegaNationalForest,Alabama.Revised.Rep.2005–02–04.Pineville,
LA:U.S.DepartmentofAgricultureForestService,ForestPestManagement.36p.
Hess,N.J.;Walkinshaw,C.H.;Otrosina,W.J.2003.Theroleofhistologyindefiningfinerootmortalityofloblollydeclinestands.Prot.Rep.R8PR–53.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,ForestHealthProtection.12p.
Hoffard,W.H.;Marx,D.H.;Brown,H.D.1995.Thehealthofsouthernforests.Prot.Rep.R8PR27.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion.36p.
Hollingsworth,R.G.;Hain,F.P.1991.Balsamwoollyadelgid(Homoptera:Adelgidae)andspruce-firdeclineinthesouthernAppalachians:assessingpestrelevanceinadamagedecosystem.FloridaEntomologist.74:179-187.
Houston,D.R.1997.Beechbarkdisease.In:Britton,K.O.,ed.Exoticpestsofeasternforests:Proceedingsofaconference.Nashville,TN:TennesseeExoticPlantPestCouncil:29–41.
Houston,D.R.;O’Brien,J.T.1983.Beechbarkdisease.ForestInsectandDiseaseLeaflet75.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Hubbes,M.1999.TheAmericanelmandDutchelmdisease.ForestryChronicle.75:265-273.
Iverson,L.R.;Prasad,A.M.;Hale,B.J.[andothers].1999.PotentialfuturedistributionsofcommontreesoftheEasternUnitedStates.Gen.Tech.Rep.NE–265.Delaware,OH:U.S.DepartmentofAgricultureForestService,NortheasternResearchStation.245p.http://www.nrs.fs.fed.us/atlas/tree/.[Dateaccessed:June11,2010].
Jetton,R.M.;Dvorak,W.S.;Whittier,W.A.2008.EcologicalandgeneticfactorsthatdefinethenaturaldistributionofCarolinahemlockintheSoutheasternUnitedStatesandtheirroleinexsituconservation.ForestEcologyandManagement.255:3212-3221.
Jetton,R.M.;Whittier,W.A.;Dvorak,W.S.;Rhea,J.R.2010.StatusofgeneconservationforeasternandCarolinahemlockintheEasternUnitedStates.In:Onken,B.;Reardon,R.,comps:Proceedingsofthe5thSymposiumonHemlockWoollyAdelgidintheEasternUnitedStates.Publicationno.FHTET-2010-07.Morgantown,WV:U.S.DepartmentofAgricultureForestService,ForestHealthTechnologyEnterpriseTeam:93-99.
Juzwik,J.;Harrington,T.C.;MacDonald,W.L.;Appel,D.N.2008.TheoriginofCeratocystisfagacearum,theoakwiltfungus.AnnualReviewofPhytopathology.46:13-26.
Kais,A.G.1989.Brownspotneedleblight.In:Cordell,C.E.;Anderson,R.L.;Hoffard,W.H.[andothers],tech.coords.Forestnurserypests.Agric.Handb.680.Washington,DC:U.S.DepartmentofAgricultureForestService:26–28.
Kasper,C.A.2000.Floweringdogwood(Cornusflorida).WindstarWildlifeInstitute.Accessedat:http://www.windstar.org/features/clearinghouse/a_flowerin.htm
Kliejunas,J.2003.ApestriskassessmentofPhytophthoraramoruminNorthAmerica.Vallejo,CA:U.S.DepartmentofAgricultureForestService,StateandPrivateForestry.11p.http://www.suddenoakdeath.org/pdf/RevisedPRA.8.03.pdf.[Dateaccessed:November22,2010].
Kliejunas,J.T.2010.SuddenoakdeathandPhytophthoraramorum:asummaryoftheliterature:2010edition.Gen.Tech.Rep.PSW-GTR-234.Albany,CA:U.S.DepartmentofAgricultureForestService,PacificSouthwestResearchStation.181p.
Koch,F.H.;Smith,W.D.2008a.Mappingsuddenoakdeathrisknationallyusinghost,climateandpathwaysdata.In:Frankel,S.J.;Kliejunas,J.T.;Palmieri,K.M.,tech.coords.2008.Proceedingsofthesuddenoakdeaththirdsciencesymposium.Albany,CA:U.S.DepartmentofAgricultureForestService,PacificSouthwestForestExperimentStation:279-287.http://www.fs.fed.us/psw/publications/documents/psw_gtr214/.[Dateaccessed:June11,2010].
489chAPTeR 16. Invasive Pests—Insects and Diseases
Koch,F.H.;Smith,W.D.2008b.Spatio-temporalanalysisofXyleborusglabratus(Coleoptera:Circulionidae:Scolytinae)invasioninEasternU.S.forests.EnvironmentalEntomology.37:442–452.
Kolarik,M.;Freeland,E.2011.Geosmithiamorbidasp.nov.,anewphytopathogenicspecieslivinginsymbiosiswiththewalnuttwigbeetle(Pityophthorusjuglandis)onJuglansinUSA.Mycologia.103(2):325-332.
Kovacs,K.F.;Haight,R.G.;McCullough,D.G.[andothers].2009.CostofpotentialemeraldashborerdamageinU.S.communities,2009-2019.EcologicalEconomics.69:569–578.
Kruse,J.J.2000.Archipsgoyeranan.sp.(Lepidoptera:Tortricidae),animportantpestofbaldcypress(Taxodiaceae)inLouisianaandMississippi.ProceedingsoftheEntomologicalSocietyofWashington.102:741–746.
Lemmen,D.S.;Warren,F.J.,eds.2004.Climatechangeimpactsandadaptation:aCanadianperspective.Ottawa,Ontario:NaturalResourcesCanada.174p.
Liebhold,A.M.;Gottschalk,K.W.;Muzika,R.[andothers].1995.SuitabilityofNorthAmericantreespeciestogypsymoth:asummaryoffieldandlaboratorytests.Gen.Tech.Rep.NE–211.Radnor,PA:U.S.DepartmentofAgricultureForestService,NortheasternForestExperimentStation.34p.
Logan,J.A.;Régnière,J.;Powell,J.A.2003.Assessingtheimpactsofglobalwarmingonforestpestdynamics.FrontiersinEcologyandtheEnvironment.1:130–137.
Loomis,R.C.1976.Loblollypinedie-off,OakmulgeeR.D.Eval.Memo.Pineville,LA:U.S.DepartmentofAgricultureForestService,ForestInsectandDiseaseManagement.2p.
Lovett,G.M.;Canham,C.D.;Arthur,M.A.[andothers].2006.ForestecosystemresponsestoexoticpestsandpathogensinEasternNorthAmerica.BioScience.56(5):395–403.
MacDonald,W.L.1995.Oakwilt:anhistoricalperspective.In:Appel,D.N.;Billings,R.F.,eds.Oakwiltperspectives:Proceedingsofthenationaloakwiltsymposium.CollegeStation,TX:TexasForestService,TexasAgriculturalExperimentStation:7–13.
Mamlstrom,C.M.;Raffa,K.F.2000.Bioticdisturbanceagentsintheborealforests:considerationsforvegetationchangemodels.GlobalChangeBiology.6:35–48.
Mausel,D.L.;Salom,S.M.;Kok,L.T.[andothers].2010.Establishmentofthehemlockwoollyadelgidpredator,Laricobiusnigrinus(Coleoptera:Derodontidae),intheEasternUnitedStates.EnvironmentalEntomology.39:440–448.
Mayfield,A.E.,III.2008.Laurelwilt.ForestandShadeTreePests,Leaflet13.Tallahassee,FL:FloridaDepartmentofAgricultureandConsumerServices,DivisionofForestry.2p.
Mayfield,A.;Barnard,E.;Bates,C.[andothers].2009.Recoveryplanforlaurelwiltonredbayandotherforestspecies.CausedbyRaffaelealauricola,vectorXyleborusglabratus.NationalPlantDiseaseRecoverySystem,acooperativeprojectofTheAmericanPhytopathologicalSocietyandTheUnitedStatesDepartmentofAgriculture.27p.http://www.ars.usda.gov/SP2UserFiles/Place/00000000/opmp/ForestLaurelWilt100107.pdf.[Dateaccessed:November29,2012].
McClure,M.S.1987.Biologyandcontrolofhemlockwoollyadelgid.Bull.851.NewHaven,CT:ConnecticutAgriculturalExperimentStation.9p.
Menard,R.D.;Eckhardt,L.G.;Hess,N.J.2006.AssessmentofloblollypinedeclineonFortBenningMilitaryReservation.Rep.2006–02–01.Pineville,LA:U.S.DepartmentofAgricultureForestService,SouthernRegion,ForestHealthProtection.21p.
Millar,C.I.;Stephenson,N.L.;Stephens,S.L.2007.Climatechangeandforestofthefuture:managinginthefacesofuncertainty.EcologicalApplications.17(8):2145–2151.
Miller,R.E.1979.Loblollypinedie-offstatusreport.Rep.79–2–4.Pineville,LA:U.S.DepartmentofAgricultureForestService,ForestInsectandDiseaseManagement.3p.
Millers,I.;Shriner,D.S.;Risso,D.1990.HistoryofhardwooddeclineintheEasternUnitedStates.Gen.Tech.Rep.NE–126.Durham,NH:U.S.DepartmentofAgricultureForestService,NortheasternArea,StateandPrivateForestry,ForestHealthProtection.75p.
Montgomery,M.E.;Bentz,S.E.;Olsen,R.T.2009.Evaluationofhemlock(Tsuga)speciesandhybridsforresistancetoAdelgestsugae(Hemiptera:Adelgidae)usingartificialinfestation.JournalofEconomicEntomology.1021(3):1247-1254.
Morris,C.L.1970.VolumelossesfromFomesannosusinloblollypineinVirginia.JournalofForestry.68:283–294.
Moser,J.C.1984.Townant.In:Proceedingsofthe10thanniversaryoftheeastTexasforestentomologyseminar.Misc.Publ.MP–1553.CollegeStation,TX:TexasAgriculturalExperimentStation:47–52.
Moser,W.K.;BarnardE.L.;Billings,R.F.[andothers].2009.ImpactsofnonnativeinvasivespeciesonU.S.forestsandrecommendationsforpolicyandmanagement.JournalofForestry.107:320–327.
Newhouse,A.E.;Schrodt,F.;Liang,H.[andothers].2007.TransgenicAmericanelmshowsreducedDutchelmdiseasesymptomsandnormalmycorrhizalcolonization.PlantCellReporter.26:977-987.
Nicholas,N.S.;Zedaker,S.M.1990.ForestdeclineandregenerationsuccessoftheGreatSmokyMountainsspruce-fir.[Abstract].In:Smith,E.R.,ed.Proceedings:thefirstannualsouthernmanandthebiosphereconference.Rep.TVA/LR/NRM–90/8.Norris,TN:TennesseeValleyAuthority.[Numberofpagesunknown].
Nord,J.C.;Ragenovich,I.;Doggett,C.A.1984.Palesweevil.ForestInsectandDiseaseLeaflet104.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Nowak,J.[N.d.].Southernpinebeetlehazardmaps.Atlanta:U.S.DepartmentofAgriculture,ForestService,SouthernRegion.http://www.fs.fed.us/foresthealth/technology/nidrm_spb.shtml.[Dateaccessed:November19,2010].
Oak,S.W.;Starkey,D.A.;Dabney,J.M.1988.Oakdeclinealtershabitatinsouthernuplandforests.In:ProceedingsoftheannualconferenceoftheSoutheasternAssociationofFishandWildlifeManagementAgencies.42:491–501.
Oliveira,E.B.;Penteado,S.R.C.;Lede,E.T.1998.ForestmanagementforthepreventionandcontrolofSirexnoctilioinPinustaeda.In:Lede,E.T.,ed.TraininginthecontrolofSirexnoctiliobytheuseofnaturalenemies:Proceedingofaconference.Morgantown,WV:U.S.DepartmentofAgriculture.104p.
Otrosina,W.L.;Garbelotto,M.2010.Heterobasidionoccidentalesp.nov.andHeterobasidionirregularenom.nov.:adispositionofNorthAmericanHeterobasidionspecies.FungalBiology.114(1):16-25.
Paine,T.D.;Birch,M.C.;Svihra,P.1981.Nichebreadthandresourcepartitioningbyfoursympatricspeciesofbarkbeetles(Coleoptera:Scolytidae).Oecologia.48:1–6.
Papadopol,C.S.2000.ImpactsofclimatewarmingonforestsinOntario:optionsforadaptationandmitigation.ForestryChronicle.76:139–149.
Paradis,A.;Elkinton,J.;Hayhoe,K.[andothers].2008.Roleofwintertemperatureandclimatechangeonthesurvivalandfuturerangeexpansionofthehemlockwoollyadelgid(Adelgestsugae)inEasternNorthAmerica.In:Mitigationandadaptationstrategiesforglobalchange.Dordrecht,Netherlands:Springer.13:541–555.
490The Southern Forest Futures Project
Parker,W.C.;Colombo,S.J.;Cherry,M.I.[andothers].2000.Thirdmillenniumforestry:whatclimatechangemightmeantoforestsandforestmanagementinOntario.ForestryChronicle.76:445–463.
Pooler,M.R.;Riedel,L.G.H.;Bentz,S.E.;Townsend,A.M.2002.Molecularmarkersusedtoverifyinterspecifichybridizationbetweenhemlock(Tsuga)species.JournaloftheAmericanSocietyforHorticulturalScience.127:623-627.
Reid,L.;Eickwort,J.;Johnson,J.;Riggins,J.J.2011.Distributionofcountieswithlaurelwiltdiseasebyyearofinitialdetection.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion.http://www.fs.fed.us/r8/foresthealth/laurelwilt/dist_map.shtml.[Dateaccessed:March9,2011].
Rexrode,C.O.;Brown,H.D.1983.Oakwilt.ForestInsectandDiseaseLeaflet29.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.
Rhea,J.R.;Watson,J.K.1994.Foresthealthevaluationofthehemlockwoollyadelgid,Adelgestsugae,infestationsinShenandoahNationalPark(SMP),Virginia,1993.Rep.94–1–22.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestHealthProtection.10p.
RiveraRojas,M.;Locatelli,B.;Billings,R.2010.CambioclimáticoyeventosepidémicosdelgorgojodescortezadordelpinoDendroctonusfrontalisenHonduras(Climatechangeandoutbreaksofthesouthernpinebeetle,Dendroctonusfrontalis,inHonduras).ForestSystems.19:70–76.
Rizzo,D.M.;Garbelotto,M.;Davidson,J.M.[andothers].2002.PhytophthoraramorumandsuddenoakdeathinCalifornia:I.Hostrelationships.In:Verner,J.,tech.ed.ProceedingsofasymposiumontheKingsRiversustainableforestecosystemproject:progressandcurrentstatus.Gen.Tech.Rep.PSW–GTR–183.Albany,CA:U.S.DepartmentofAgricultureForestService,PacificSouthwestResearchStation:733–740.
Robbins,K.1984.Annosusrootrotineasternconifers.ForestInsectandDiseaseLeaflet76.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.
Rogers,H.H.;Runion,G.B.;Krupa,S.V.1994.PlantresponsestoatmosphericCO2enrichmentwithemphasisonrootsandtherhizosphere.EnvironmentalPollution.83:155–189.
Scheffer,R.J.;Voeten,J.G.W.;Guries,R.P.2008.BiologicalcontrolofDuctchelmdisease.PlantDisease.92:192-200.
Scherm,H.2004.Climatechange:canwepredicttheimpactsonplantpathologyandpestmanagement?CanadianJournalofPlantPathology.26:267–273.
Schlarbaum,S.E.1988.ReturningtheAmericanchestnuttotheforestsofNorthAmerica.KatuahJournal.21(Fall):6,7,23.
Seem,R.C.2004.Forecastingplantdiseaseinachangingclimate:aquestionofscale.CanadianJournalPlantPathology.26:274–283.
Seybold,S.;Haugen,D.;O’Brien,J.[andothers].2010.Thousandcankersdisease.PestAlertNA–PR–02–10.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NortheasternArea,StateandPrivateForestry.2p.http://na.fs.fed.us/pubs/palerts/cankers_disease/thousand_cankers_disease_screen_res.pdf.[Dateaccessed:January10,2011].
Sharov,A.;Leonard,D.;Liebold,A.M.[andothers].2002.“Slowthespread”:anationalprogramtocontainthegypsymoth.JournalofForestry.100:30–35.
Smith,E.L.;Storer,A.J.;Roosien,B.K.2009.EmeraldashborerinfestationratesinMichigan,Ohio,andIndiana.[Abstract].In:McManus,K.A.;Gottschalk,K.W.,eds.Proceedings.20thU.S.DepartmentofAgricultureinteragencyresearchforumoninvasivespecies.Gen.Tech.Rep.NRS–P–51.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NorthernResearchStation:96.
Smith,R.H.;Lee,R.E.,III.1972.Blackturpentinebeetle.ForestPestLeaflet12.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Snover-Clift,K.L.2009.Dutchelmdisease:Ophiostomanovo-ulmi.Factsheet.Ithica,NY:CornellUniversity,PlantDiagnosticClinic.4p.http://plantclinic.cornell.edu/factsheets/dutchelmdisease.pdf.[Dateaccessed:March11,2011].
Solomon,J.D.1995.GuidetoinsectborersofNorthAmericanbroadleaftreesandshrubs.Agric.Handb.706.Washington,DC:U.S.DepartmentofAgricultureForestService.706p.
SouthernAppalachianManandtheBiosphere.1996.TheeffectstoSouthernAppalachianAssessmentforestecosystemsfromnativeandexoticpests.In:TheSouthernAppalachianassessmentterrestrialtechnicalreport.Rep.5of5.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion:103-122.
Spittlehouse,D.L.;Stewart,R.B.2003.Adaptationtoclimatechangeinforestmanagement.BCJournalofEcosystemsandManagement.4(1):1–11.http://www.forrex.org/publications/jem/ISS21/vol4_no1_art1.pdf.[Dateaccessed:November22,2010].
Staeben,J.C.;Clarke,S.;Ghandi,K.J.K.2010.Blackturpentinebeetle.ForestInsectandDiseaseLeaflet12.Portland,OR:U.S.DepartmentofAgricultureForestService.8p.
Staley,J.M.1965.Declineandmortalityofredandscarletoaks.ForestScience.11:2–17.
Stambaugh,W.J.1989.AnnosusrootdiseaseinEuropeandtheSoutheasternUnitedStates:occurrence,research,andhistoricalperspective.In:Otrosina,W.J.;Scharpf,R.F.,tech.coords.Proceedingsofthesymposiumonresearchandmanagementofannosusrootdisease(Heterobasidionannosum)inWesternNorthAmerica.Gen.Tech.Rep.PSW–116.Berkeley,CA:U.S.DepartmentofAgricultureForestService,PacificSouthwestForestandRangeExperimentStation:3–9.
Starkey,D.A.;Mangini,A.;Oliveria,F.[andothers].2000.ForesthealthevaluationofoakmortalityanddeclineontheOzarkNationalForest,1999.Rep.2000–02–02.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestHealthProtection.31p.
Starkey,D.A.;Oak,S.W.;Ryan,G.[andothers].1989.EvaluationofoakdeclineareasintheSouth.Prot.Rep.R8PR–17.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestPestManagement.43p.
Sturrock,R.N.2007.Climatechangeeffectsonforestdiseases:anoverview.In:Jackson,M.B.,comp.Proceedingsofthe54thannualwesterninternationalforestdiseaseworkconference.Missoula,MT:U.S.DepartmentofAgricultureForestService:51–55.
Sturrock,R.N.;Frankel,S.J.;Brown,A.V.[andothers].2011.Climatechangeandforestdiseases.PlantPathology.60:133-149.
Tainter,F.H.;Baker,F.A.1996.Oakwilt.In:Principlesofforestpathology.NewYork:JohnWiley:671-682.
Tainter,F.H.;Retzlaff,W.A.;Starkey,D.A.;Oak,S.W.1990.Declineofradialgrowthinredoaksisassociatedwithshort-termchangesinclimate.EuropeanJournalofForestPathology.20:95–105.
TexasForestService.1982.Texasforestpestreport1980–1981.Publ.127.CollegeStation,TX:TexasForestService.39p.
Thatcher,R.C.1960a.Barkbeetlesaffectingsouthernpines:areviewofcurrentknowledge.Occas.Pap.180.Washington,DC:U.S.DepartmentofAgricultureForestService.25p.
Thatcher,R.C.1960b.Influenceofthepitch-eatingweevilonpineregenerationineastTexas.ForestScience.6:354–361.
Thatcher,R.C.;Barry,P.J.1982.Southernpinebeetle.ForestInsectandDiseaseLeaflet49.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.
491chAPTeR 16. Invasive Pests—Insects and Diseases
Thatcher,R.C.;Conner,M.D.1985.Identificationandbiologyofsouthernpinebarkbeetles.Agric.Handb.634.Washington,DC:U.S.DepartmentofAgricultureForestService;CooperativeStateResearchService,ExpandedSouthernPineBeetleResearchandApplicationsProgram.14p.
Thatcher,R.C.;Coster,J.E.;Hertel,G.[andothers],eds.1980.Thesouthernpinebeetle.Tech.Bull.1631.Washington,DC:U.S.DepartmentofAgricultureForestService,ScienceandEducationAdministration,ExpandedSouthernPineBeetleResearchandApplicationsProgram.266p.
Tran,J.K.;Ylioja,T.;Billings,R.[andothers].2007.ImpactofminimumwintertemperaturesonthepopulationdynamicsofDendroctonusfrontalis(Coleoptera:Scolytinae).EcologicalApplications.17:882–899.
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2003.Emeraldashborer;quarantineandregulations:interimruleandrequestforcomment.FederalRegister.68:59,082–59,091.
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2006.Emeraldashborer;quarantinedareas:affirmationofinterimrulesasfinalrule.FederalRegister.70:249–263.
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2010a.APHISlistofregulatedhostsandplantsprovenorassociatedwithPhytophthoraramorum.http://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/pdf_files/usdaprlist.pdf.[Dateaccessed:March4,2011].
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2010b.Europeangypsymoth(Lymantriadispar)NorthAmericaquarantine.Washington,DC:U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.http://www.aphis.usda.gov/plant_health/plant_pest_info/gypsy_moth/downloads/gypmoth.pdf.[Dateaccessed:November19,2010].
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2011.Cooperativeemeraldashborerproject:EABlocationsinIllinois,Indiana,Iowa,Kentucky,Maryland,Michigan,Minnesota,Missouri,NewYork,Ohio,Pennsylvania,Virginia,Wisconsin,WestVirginiaandCanada:February1,2011.http://www.emeraldashborer.info/files/MultiState_EABpos.pdf.[Dateaccessed:March1,2011].
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService,AgriculturalResearchService,ForestService;CooperatingStateDepartmentsofAgriculture.2010.Emeraldashborer,Agrilusplanipennis(Fairmaire),biologicalcontrolreleaseguidelines,ver.1.Riverdale,MD:U.S.DepartmentofAgriculture,Animal&PlantHealthInspectionService.63p.
U.S.DepartmentofAgricultureForestService.1985a.BlackturpentinebeetleandIpsbeetles.In:Insectsofeasternforests.Misc.Publ.1426.Washington,DC:U.S.DepartmentofAgricultureForestService:346–347,358–361.
U.S.DepartmentofAgricultureForestService.1985b.Foresttentcaterpillar.In:Insectsofeasternforests.Misc.Publ.1426.Washington,DC:U.S.DepartmentofAgricultureForestService:204-205.
U.S.DepartmentofAgricultureForestService.2010.Hemlockwoollyadelgid[homepage].NewtownSquare,PA.:U.S.DepartmentofAgricultureForestService,NortheasternArea.http://www.na.fs.fed.us/fhp/eab/.[Dateaccessed:March1,2011].
U.S.DepartmentofAgricultureForestService,andUSDAAnimalandPlantHealthInspectionService.2008.Asianlonghornedbeetle:anewintroduction.PestAlertNA–PR–01–99GEN.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService;AnimalandPlantHealthInspectionService.2p.http://www.na.fs.fed.us/pubs/palerts/alb/alb_pa.pdf.[Dateaccessed:November22,2010].
U.S.DepartmentofAgricultureNaturalResourcesConservationService.2008.TennesseeNaturalHeritageProgramrareplantlist2008.Nashville,TN:TennesseeDivisionofEnvironmentandConservation,DivisionofNaturalResources.46p.http://www.state.tn.us/environment/na/pdf/plant_list.pdf.[Dateaccessed:February18,2011].
U.S.DepartmentofAgricultureNaturalResourcesConservationService.2009.Countyreportofendangered,threatenedandspecialconcernplants,animals,andnaturalcommunitiesofKentucky.Frankfort,KY:KentuckyNaturePreservesCommission.136p.http://plants.usda.gov/java/threat?statelist=states&stateSelect=US21.[Dateaccessed:February18,2011].
U.S.DepartmentofAgricultureNaturalResourcesConservationService.2011.Threatenedandendangered:protectedplantsforscientificname=Juglanscinerea.http://plants.usda.gov/java/threat?txtparm=Juglans+cinerea&category=sciname&familycategory=DI&duration=PR&growthhabit=TR&wetland=all&statefed=statelist&stateSelect=US01&stateSelect=US05&stateSelect=US12&stateSelect=US13&stateSelect=US21&stateSelect=US22&stateSelect=US28&stateSelect=US37&stateSelect=US40&stateSelect=US45&stateSelect=US48&stateSelect=US51&stateSelect=US72&sort=sciname&submit.x=84&submit.y=13.[Dateaccessed:February18,2011].
Vilela,E.F.1986.Statusofleaf-cuttingantcontrolinforestplantationsinBrazil.In:Lofgren,C.S.;VanderMeer,R.K.,eds.Fireantsandleaf-cuttingants:biologyandmanagement.Boulder,CO:WestviewPress:399-408.
Ward,J.D.;Mistretta,P.A.2002.Impactofpestsonforesthealth.In:Wear,D.N.;Greis,J.G.Southernforestresourceassessment.Gen.Tech.Rep.SRS–53.Asheville,NC:U.S.DepartmentofAgricultureForestService,SouthernResearchStation:403-428.Chapter17.
Wargo,P.M.1977.ArmillariamelleaandAgrilusbilineatusandmortalityofdefoliatedoaktrees.ForestScience.23:485–492.
Wargo,P.M.;Harrington,T.C.1991.Hoststressandsusceptibilitytoarmillaria.Agric.Handb.691.In:Shaw,C.G.,III;Kile,G.,eds.Armillariarootdisease.Washington,DC:U.S.DepartmentofAgriculture:88–101.
Wargo,P.M.;Houston,D.R.;LaMadeleine,L.A.1983.Oakdecline.ForestInsectandDiseaseLeaflet165.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.
Winnett,S.M.1998.PotentialeffectsofclimatechangeonU.S.forests:areview.ClimateResearch.11:39–49.http://www.int-res.com/articles/cr/11/c011p039.pdf.[Dateaccessed:November22,2010].
Woods,A.J.;Coates,K.D.;Hamann,A.2005.IsanunprecedentedDothistromaneedleblightepidemicrelatedtoclimatechange?BioScience.55:761–769.
Zhu,Z.1994.Forestdensitymappinginthelower48States:aregressionprocedure.Res.Pap.SO–280.NewOrleans:U.S.DepartmentofAgricultureForestService,SouthernForestExperimentStation.11p.
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andallvegetation.Newplantcommunitieswillorganizethemselvesandwillreplaceplantsthatareunabletoadapttonewclimates.Newcommunitiescouldincludecurrenttreespecies,othertreespecies(e.g.,hardwoodsorstronglydispersingspeciesfromwarmerareas)orcouldbecomedominatedbygrassandshrubspecies.
moDeliNG climATe chANGe
Available models
Majoreffortsareunderwaytocreateandusemodelsthatcanprojectpotentialscenariosdescribingboththeimpactsofclimatechangeonecologicalconditionsandthesubsequentresponsesresultingfromandpossiblytheninfluencingthoseconditions.Modelingcancontributetoourprojectionsoffutureconditions“…butrequiressoundknowledgeofthecausalfactorsdeterminingspatialdistribution,survival,reproduction,dispersal,andinflictionofdamage”(GoudriaanandZadocks1995).
Selectionofbroad-scalemodeltypes(suchasgeneralcirculationmodels,process-basedmodels,andempiricalmodels)dependsonthespecificquestionsbeinganalyzedandtheavailablerelevantdata.Theapplicationofgeneralcirculationmodelsislimited;thefinestscaleusedforglobalclimatesimulationisfartoocoarseformeaningfulecologicalapplications(Loganandothers2003).Atasmallerscale,gapmodels,biogeographymodels,andbiogeochemistrymodelsareamongthosebeingusedtorefineprobablebroad-scalemodelprojectionstoreflectconditionsatamorelocalscale(Winnett1998).
Currentmodelprojectionsoffutureconditionsthatwillaffectforestcompositionandproductivityvaryoverawiderangeofplausiblescenarios(Loganandothers2003,NationalAssessmentSynthesisTeam2000,Scherm2000).
Scherm(2000)supportsMillstein’s(1994)contentionthatuncertaintiesinmodelinputcancompromisethecredibilityoftheoutputbecauseoferrorperpetuationorpropagation.Thesescientistsarenotaloneintheirconcern.Othersaddtheconcernthatdataselectioncanalsosignificantlyinfluence
iNTRoDucTioN
Thisappendixcontainsageneralizedsummaryoftherelevantliteraturerelatedtoclimatechange,vegetationchange(speciesandgeographicrangechanges),andpestactivityscenarioclassificationasreflectedinthecurrentliterature.
Informationforthisappendixwasderivedfrompublishedscienceliterature,alongwithaselectionofliteratureaboutthebiologyandecologyofforestpests.AdditionalinformationaboutforestpestsandtheircontrolisreadilyavailablefromStateandFederalforestryagenciesoronline(twogoodstartingpointsarehttp://na.fs.fed.us/pubs/index.shtmandhttp://www.fs.fed.us/r8/foresthealth/).
Manyscientistsbelievethatclimatechangeintheformofglobalwarminghasoccurredoverthelastcenturyandwillcontinuetooccurintotheimmediatefuture(IntergovernmentalPanelonClimateChange2007,Kleijunasandothers2009,MalcolmandPitelka2000,McNultyandAber2001,NationalAssessmentSynthesisTeam2000).Theprimaryfactorsofclimatenotedasdrivingobservedecologicaleffectsaretemperatureandavailablewater.Inadditionatmosphericgasses(carbondioxideandairpollutantssuchasnitrogenoxidesandsulfurdioxide)inexcessoftheir‘normal’rangesareoftenidentifiedasadditionaldriversofthechangebeingobserved.Climatechangeisalsolinked,atleastinpart,tohumanactivity(MalcolmandPitelka2000,Sturrock2007,Winnett1998).Thesechangesareexpectedtoimpactcropsandtheirpestsindividually,aswellasimpactingtheinteractionsbetweencropsandpests(Runion2003).
Reportingtheresultsofaworkshopattemptingtounderstandthepotentialinteractionsamongforests,insects,diseases,andclimatechange,Beukemaandothers(2007)reportthat:
Participantsagreedthatthingswillchange.Mostvegetationcommunitieswillnotsimplymigratefromonelocationtoanother.Instead,manycommunitieswillbecompletelynew,withnewcombinationsoftrees,understoryplants,insects,anddiseases.Atthesametimeitisimportanttobearinmindthatwearenotgoingtocompletelyloseallforests
appeNDIX C. climate change and its impacts on Forests
494The Southern Forest Futures Project
modeloutput.Theuseofacrispdatasetversusa“fuzzynumber”setwillhaveadditionalmajorimpactsonoutputs(Coakleyandothers1999).
SchermandCoakley(2003)haveidentifiedthreecontinuingproblemswiththeapplicationofmodelsforpredictingclimatechangeeffects:
• Modelinputshaveahighdegreeofuncertainty.
• Nonlinearrelationshipsandthresholdsintherelationshipbetweenclimaticvariablesandepidemiologicalresponsescomplicateeffortstocollectsufficientdataforclearpredictiveunderstanding.
• Modelingoftenignoresthepotentialforadaptationbyplantsandtheinsectsanddiseasesthatattackthem.
Physical impacts of climate change
Temperature—Increaseinaveragetemperatureisconsistentlyshowninresultsfromavarietyofmodelsasbeingofconcern.TheIntergovernmentalPanelonClimateChange(2007)statedthatthedatasupportinganongoingwarmingoftheclimateareunequivocal,pointingtoobservationsofincreasesinglobalairandoceantemperatures,widespreadmeltingofsnowandice,andrisingsealevels.Thepanelfoundalineartrendinaveragetemperaturewhichhadincreasedby0.74ºC(0.56to0.92ºC)from1906to2005,higherthantheearlierreportedincreaseof0.6ºC(0.4to0.8ºC)for1901to2000(IntergovernmentalPanelonClimateChange2001);thatlandareashavewarmedfasterthanoceans;andthattemperatureincreasesappeartobelargerinnorthernlatitudes.
Overall,climatechangeispredictedtoleadtoincreasingtemperature.Meanglobalsurfaceairtemperaturesarepredictedtoincreasefrom1.4to5.8ºCbytheendofthecentury.Bothnight-dayandwinter-summeraveragetemperaturerangesarelikelytoshrinkasminimumtemperaturesincreasemorethanmaximumones,andcontinentalandhigh-latitudeareaswilltendtowarmmorethancoastalandlower-latitudeareas(Burdonandothers2006,Harvellandothers2002).Themagnitudeofthesechangesisexpectedtovarybothtemporallyandspatially(McNultyandBoggs2010).
Water regime—Waterisreportedtobeofgreatsignificance,secondonlytotemperature,whenprojectingpotentialeffectsofclimatechange.Overabundanceofwater,lackofit,andseasonalityofitsavailabilityallhavesignificantimpactsontheforestprocessesthatgoverntheoverallhealthofindividualorganisms.Projectionsofoverallresponsestorainfallpatternvarygreatly.Generalizationsfoundintheliteratureincludethefollowing:
• IntheSouth,intenseprecipitationeventshaveincreasedoverthepast100years(NationalAssessmentSynthesisTeam2000).
• Risingsealevelshavealreadyhadsignificantimpactsoncoastalareas,andtheseimpactswilllikelyincrease(NationalAssessmentSynthesisTeam2000).
MalcolmandPitelka(2000)summarizedtheeffectsofwaterasfollows:futureregional-scaleprecipitationchangesremainparticularlydifficulttopredict,andchangesinthefrequencyandseverityofstormsandotherextremeweathereventsareuncertain(Wigley1999).Overallthesechangeswillappearasashiftofclimaticzonestowardsthepoles;warmertemperatureswillreachfurthernorthintheUnitedStates.Thislastobservationintroducesacriticalconcernwhendiscussingclimatechange.Ecologicalfactorsdonotfunctioninisolation,theyinteractandinfluenceeachother.Thisisafacteasilyforgottenwhenreadingtheliterature,muchofwhichdiscussessinglefactoreffectsatavarietyofscales.
Carbon dioxide and trace gases—Carbondioxideisroutinelycitedasaprimarycauseofglobalwarming.Theconsensuswithinthescientificcommunity(Coakley1988)isthattheincreaseincarbondioxideandshiftingpercentageoftracegases(ozone,chlorofluorocarbons,nitrogenoxides,sulfuroxides,andmethane)willcombinetobringaboutcontinuingglobalwarming.Althoughthisisgenerallyagreedtobeanaccurateprojectionoffuturecondition,thespatialrelationshipsinvolvedareextremelyuncertain,asarepredictionsofwheretheeffectwillbesignificant.
Light—Solarradiationisthesourceofenergyformostterrestrialprocesses,andanythingthatalterstheamountofradiationreachingtheearth’ssurfacemayalterclimate.Fluctuationsinsolaroutput,volcaniceruptions,andothernaturalperturbationsinfluencesolarinputtotheearth’senergyengine,asdochangesinlanduseandindustry.Thequalityoflightandthedurationofphotoperiodhavebeenshowntoaffectplantsinavarietyofways.Yetexcepttonotethatgreenhousegassescanaffectthequalityoflight,littleissaidintheliteratureaboutpossiblefutureshiftsinlightquality.Photoperiodisseldomdiscussedaschangingforagivenarea.Effectsofphotoperiodonlyappeartobenotedassignificantwithinthecontextofotherfactorsthatinfluenceplantmigrationsasdescribedbelow.
Wind—Intheearly1950s,Hepting(1963)foundthatwind,nottemperatureorrainfall,wastheprimarydriverofclimatechangeinGreatBritain.Morerecently,LemmenandWarren(2004),alsodiscussingclimatechangeinGreatBritain,suggestthatawarmerclimatemaybemoreconducivetoextremewindeventsandthatthesemayinturnhaveconsequencesforotherforestdisturbances.Yarwood(1959)suggestedthatwindhassignificantimpacts,both
495chAPTeR 16. Invasive Pests—Insects and Diseases
directlyorindirectly,onplantsandthepeststhatattackthem.Unfortunately,withtheexceptionofdiscussionsinthecontextofstormevents,windislittlediscussedintheliterature,andwefoundnoprojectionsoffuturewindeventsintheSouth.
Soil—Soilchemicalpropertiesdonotappeartobedirectlyaffectedbyclimatechange,theironlycontributiontoclimatechangebeingacomplexofsecondaryeffects.However,itisgenerallyrecognizedthatasairtemperatureincreasessodoessoiltemperature.Soilwarminginconjunctionwithdroughtisamajorconcernbecauseitpredisposesrootsandrootletstomortality,whetherornotrootrottingfungiareinvolved.Localizedandoftenshort-termshiftsinthealbedoarepredictedifsoilwarmingresultsinthefailureofvegetativecover,butpredictionsarenotspatiallyexpliciteitherastosizeorlocation.
Ratesofsoilmineralization,acidification,nitrification,andcarbonsequestrationareallprocessesthatareclearlyinfluencedbyclimatechange,butgenerallytheseeffectsaremoreaffectedby(andsubsequentlyinfluence)thelocalbiota.
Mixed edaphic effect projections—Avarietyofprojectionshavebeenmadeforcompoundededaphicfactors;fourarebrieflynotedbelow:
• Increasedfrequencyofextremeweatherevents(Scherm2003)
• Increasedfrequencyandintensityofdroughtoccurringunderwarmertemperatures(Breshearsandothers2005)
• Morefrequentwinterwaterloggingresultingfromincreasedwinterrainfall(BroadmeadowandRay2005)
• Increaseddurationofsunshineresultingfromchangesintemperatureandhumiditywhichinturnleadtoreducedsummercloudcover(BroadmeadowandRay2005)
imPAcTS oN PeSTS AND iNDiViDuAl hoST PlANTS
Climateisthesinglemostimportantfactordeterminingthedistributionofmajorvegetationtypesandindividualspecies(MalcolmandPitelka2000).
Extrapolatingthephysicaleffectsofclimatechangetothepotentialbiological/ecologicaleffectsthattheyengenderisoftenproblematic.Thesimpledescriptionisthatastheclimatewarms,southernforestswillmigratenorthwardandupward(assumingthathigherelevationsitesbecomeavailable),andwilldisplaceaportionofthetemperatemixedhardwoodforest.Thetemperatemixedhardwood
forestinitsturnwillmigrate,displacingpartofthenorthernborealforest.Althoughthispresentsaneasytounderstandgeneralization,itmasksanextremelycomplexreality.
Forestsarenotexpectedtomigrateascohesiveunits.Althoughdrivenbyasetofindividualphysicalparameters,migrationwillmorelikelyresponddirectlyatthespeciesandindividualplantlevel,notattheassociation,ecosystem,orotherecologicalleveloforganization.Differentspecies(anddifferentindividualsevenwithinaspecies)willreactinpotentiallyverydifferentwaystothevariousstimuligeneratedbyclimatechange.Theresponsesofecosystemscanonlybepredictedbyunderstandingthebehavioroftheirconvergentpropertiesandtheuniquecharacteristicsandresponsesofindividualspecies(MalcolmandPitelka2000).
Onthepositiveside,increasinglysophisticatedcomputermodelshavebeendevelopedthatincorporatemorefundamentalecologicalmechanisms.However,eventhesenewermodelscannotyetpredictwithaccuracywhathappensastheclimateischanging(MalcolmandPitelka2000).
Nevertheless,wehavesomeclearreportsofobservedresponsestoclimatechange.Anaverage1°Cincreaseinaveragetemperatureisreportedtoincreaseplantgrowthandlengthenthegrowingseason.Budbreakofquakingaspen(Populustremuloides)isreportedtobe26daysearlierthanacenturyagoinAlberta,Canada;andbudbreakofwhitespruce(Piceaglauca)isearlierinOntario(LemmenandWarren2004).Ground-basedmonitoringeffortsinEuropedocumentedan11-dayincreaseingrowingseasonlengthovera34-yearperiod(MalcolmandPitelka2000).Becausetemperaturecanaffectecosystemsinmanydifferentwaysandbecausetherearemultiplepathwaysforfeedbackandinteraction,evaluatingorpredictingtheeffectsoftemperatureincreasesisnotsimple.Notsurprisingly,publishedresultshavebeenmixed(MalcolmandPitelka2000).
Thesizeofplantorgansatmultiplescalesmayincreaseasaresponsetoelevatedlevelsofcarbondioxide.Increasedareaperleaf,leafthickness,numberofleaves,leafareaperplant,anddiameterofstemsandbrancheshaveallbeenobservedunderincreasedcarbondioxide.Enhancedphotosynthesis,increasedwateruseefficiency,andreduceddamagefromozonearealsoreportedasresponsestoincreasedcarbondioxide(Garrettandothers2006).
Disease and insect Risks, Absent climate change
ThesecondperiodicNationalInsectandDiseaseRiskMap,completedin2006,presentsastrategicassessmentofpotentialtreemortalityresultingfrommajorinsectsanddiseases.Thisisthedefinitivesourceatthepresenttimeforprojectedinsect-anddisease-causedmortality
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Zadocks1995).Althoughthenumberofrecentattributionsofpathosystemshiftsresultingfromclimatechangeisincreasing,fieldresearchisplaguedbythelong-termnatureofclimatechange,whichismuchmorecomplicatedthantheshiftsinweatherthathavebeenmorecommonlystudiedinthepast(Coakley1988).
Host-pestinteractionswillbeaffectedbyclimatechangeinsimilarwaysasotherplantsandanimals.Inthemostsimplisticscenario,pestspeciesmigrationswillgenerallyfollowthemigrationoftheirpreferredhosts.Allofthesameecologicalelementsaffectingthehostsinthenewenvironmentwillimpactthepeststhemselves.Temperature,availablewater,qualityanddurationoflight,airquality,soilcondition,andotherfactorswillaffecttheirphysiologicalandecologicalresponses.Inaddition,theconditionandpossiblyalteredphysiologyofthehostinitsnewenvironmentwillinfluencethenewhost-pestinteraction.
Diseaseevolutionisanotherfactorthatpresentscomplicationswhenpredictingthemigrationofdiseasesintonewareas;ratesaredeterminedbythenumberofgenerationsofreproductionpertimeinterval,alongwiththeheritabilityoftraitsrelatedtofitnessunderthenewclimatescenario(Garrettandothers2006).
Afewrecentpublicationshavefocusedontheneedtoconsidermicroclimatefactorsasbeingimmediatelyrelevantwhendescribingpest-hostinteractions.Thisisalittlestudiedareaduetothecomplexityinherentinisolatingmicro-effectsinamacro-scaleecosystem.
Temperature effects on diseases—Gradualwarmingwouldprobablyleadtoageneralnortherlyshiftinseasonalclimaticregimes,whichinturnwouldaffecttherangeofoak(Quercusspp.),sometimesadverselyandsometimesfavorably(BrasierandScott1994).Newdiseasecomplexesmayariseandsomediseasesmayceasetobeeconomicallyimportantifwarmingcausesapolewardshiftofagroclimaticzonesandhostplantsmigratebeyondtheircurrentranges.Pathogenswouldfollowthemigratinghostsandmayinfectremnantvegetationofnaturalplantcommunitiesnotpreviouslyexposed(Coakleyandothers1999).
Thegeographicrangeoffungalpathogensaretosomeextentdeterminedbythetemperaturerangesoverwhichtheycangrow(LonsdaleandGibbs1994).BrasierandScott(1994)foundthatthegrowthanddevelopmentofmanyfungiwithinthehostmayoftenbefavoredbyclimatewarming,andtheconditionsthatprevailwhenfungiarriveatthehostsurfaceareoftencriticalfordiseaseestablishment;theyalsoobservedthattheeffectsoftemperatureonthedevelopmentandpopulationdynamicsofmanypotentialoakdiseaseshavebeenlittleresearchedandtheyidentifiedthedifficultiesinvolved.Nevertheless,theypredictedthat
aswarmingincreasesinEurope,arootrotdisease(causedbyPhytophthoracinnamomi)willextenditsnorthwardrange,survivewintersbetterinrootsystems,showincreasedspreadwithinthehost,havegreaterinfectionfrequencyofnewhosts,andcausemarkedlymorerapidhostdeclineandmortality.
OtherauthorsconcurwiththepredictionsofBrasierandScott(1994).Chakrabortyandothers(1998)pointoutthatchangesintemperaturewillalterhost-plantphysiologyandthushostresistancetopests.BroadmeadowandRay(2005)addthatincreasedtemperatureswillresultinhigherevapotranspiration.AndBurdonandothers(2006)reiteratethatwhenweturntotheimpactofthemoreunpredictableaspectsofglobalclimatechangeonthepathogensthemselves,wewilllikelyseesignificantchangesinhost-pathogeninteractionsovertime,whicharelikelyinbothdirections(increaseanddecreasedactivity).
Increasedsoiltemperaturehasbeenshowntohavenegativeeffectsonplantroots.Redmond(1955)reportedthatina55-yearoldstand,yellowbirch(Betulaalleghaniensis)rootletswithanormalbackgroundmortalityrateofabout6percentsuffered19percentrootmortalitywhenaveragesoiltemperatureincreased1°Cand60percentrootmortalityifthetemperatureaverageincreased2°C.Theyalsoreportedachangeinmicrobialpopulationandachangeinthedevelopmentofmycorrhizae,thesymbioticassociationsbetweenfinefeederrootsofplantsandroot-inhabitingfungi.
Becauseoftheirrapidresponsetosmallenvironmentalchanges,pathogensmayprovidegoodearlywarningofimpendingclimatechange.Thedamagethresholdfromadiseasemayalsochangeinanewgeographicallocation(Chakrabortyandothers1998).
Temperature effects on insect pests—Higherairtemperaturescommonlyenhancethegeneralactivity,populationsize,andpotentialfordispersalofinsectpests.Highertemperaturescouldleadtogreateroverwinteringpopulationsize,increasedlengthofflightseason,andlengthofdailyflightperiods(BrasierandScott1994).Continuedclimatechange,andparticularlywarming,wouldhaveadramaticimpactonpestinsectspecies.Ascold-bloodedorganisms,theyhavealifehistorythathingesontemperature;thermalhabitatlargelysetstheboundariesoftheirgeographicdistribution(Loganandothers2003).
Extendedperiodsofwarmweathercanfavorthedevelopmentofinsectpestsbothdirectlyandindirectly.Warmtemperaturescanacceleratethedevelopmentofinsectpopulationsbyreducingthetimeneededforlife-cyclecompletion.Indirecteffectscanbetheresultofchangesinthehostplant,orcanbeproducedbydecouplingrelationshipswithnaturalenemies(MamlstromandRaffa
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2000).Insomecircumstances,warmertemperaturescouldactuallyinhibitinsectactivityordisruptthebuildupofpopulations:althoughwarmerwinterswouldincreaseoverwintersurvivalofsomeinsectpests,reducedsnowcovercouldincreasethewintermortalityofothers(Burdonandothers2006).Enemiesofinsectpestswouldalsobeaffectedbyclimatechange,buttheseeffectsaregenerallyunknownandrequiremoreresearch.Ifwarmertemperaturesfavorpredatorsandparasitoids,thesenaturalenemiesofpestswillexhibitgreatercontrolofthosepestspecies.Conversely,ifwarmertemperaturesdisruptordecreasepredatorandparasitoidpopulations,pestpopulationswillgrowmorequicklyandwillpersistathigherlevelsforlongerperiodsoftime.
Available water effects—Gilmour(1960)identifiedtwooppositewaterrelatedconditionsthatcausesignificantimpactsontrees.Droughtconditionshavebeenshowntobethecauseofvariousdisorderswithorwithoutanyassociatedfungalpathogen.And,saturatedsoilhasbeenfoundtocausedisordersinmanyplants.Thus,bothextremesinwateravailabilityhavebeenshowntonegativelyaffecttrees.Saturatedsoils,althoughbeingsomewhatdeficientinoxygen,appearalsotohavealteredchemistryfromsimilardriersoils.Garrettandothers(2006)foundthatevenwithouttheaddedimpetusofclimatechangetheinteractionofprecipitationanddiseaseisofprimaryimportanceforpredictingdiseaseseverity.
BroadmeadowandRay(2005)foundthatincreasedwinterrainfallleadstomorefrequentwinterwaterloggingofsoiland,insomecircumstances,tofinerootdeathextendingintothesoilsurfacehorizons.Thisinturnexacerbatestheeffectsofsubsequentsummerdrought.Blackandothers(2010)associatedSwissneedlecastdisease(Phaeocryptopusgäumannii)withspringandsummerneedlewetness,aswellaswintertimetemperatures.
Becausemostplantparasiticfungiarebelievedtorequirefreewaterforsporegermination,microclimateofleafsurfacesisanimportantconsideration.Theimportantsourcesoffreewaterforfoliagediseasesarerain,fog,condensedwater,andguttationwater.Yarwood(1959)foundlittlegerminationwhentherelativehumidityfellbelow95percentandcategorizedfoliagediseasesbytheirrequirementsforwaterinthephyllosphereduringtheinfectionstage;but,insteadofpresentingabroadcategorizationofthiseffect,focusedattentiononrustfungi(specificallytheirurediosporestage).
LemmenandWarren(2004)emphasizethatforestcharacteristicsandage-classstructurealsoaffecthowforestsrespondtochangesinmoisture,notingthatmatureforests(withwellestablishedrootsystems)arelesssensitivetochangesinmoisturethanyoungerforestsand
post-disturbancestands—atleastintheshortrun.Theyaddthatdifferentspecieshavedifferentdroughttolerance,whichalsomustbeconsidered.AndLonsdaleandGibbs(1994)remindusthatclimatechangewithitsassociatedchangeinfrequencyofsummerdroughtswouldalterthestabilityofassociationsbetweentreespeciesandvariousmembersoftheirnon-diseasefungalassociations—resultinginanoutbreakofdiseaseinplaceofcoexistence,orinsomecircumstancesmutualism.
Hansonandothers(2001)foundthattheimpactofpotentialchangesindroughtorprecipitationregimeswillnotonlydependonthepredictedscenarioofchange,butalsoonthetypeofforestecosystemandtheclimateconditionstowhichitiscurrentlyadapted.Theyconcludebysummarizingsixreasonswhyforestswouldnotexhibitcatastrophicdiebackundertheinfluenceofclimatechange(includingdrought)andthepredictionthatthereplacementofforestsbyfastergrowingtreeswillbegradual(Loehle1996).
Generallyspeaking,anyprecipitationregimethatstresseshosttrees(whetheritistoolittleortoomuchmoisture)willmakethemmoresusceptibletoinsectattack.
Wind effects—Yarwood(1959)citeswindasbeingaseriousmodifierofwaterrelationsandsuggeststhatwindcommonlypreventstheformationofdew,andcausesraindropsordewtoevaporatemorerapidlythantheywouldinstillair.BroadmeadowandRay(2005)notethatanincreaseinthenumberofstormsmaymakewoodlandsmorevulnerabletowinddamage.
Light effects—Fungipreferentiallygrowwhentheskyiscloudyandarethereforeactivemainlyonshadedpartsoftheplantorinnon-irradiatedanglesoftheecosystem.Pathogenicfungiareadditionallyprotectedwhengrowingpartlyorcompletelywithinthehost’stissue(ManningandvonTiedemann1995).
Thegreatsignificanceoflightespeciallyinthenearultravioletband(UV-A)onfungalsporulationhasbeenrecognizedsincethefirststudieswereperformedonthisphenomenoninthe1960s.Humphrey(1941)reportsthatexposuretolightstimulatedsporulationin62of75speciesoffungitested;mostrequiredlightfortheinitiationofsporulation.Sporulationwasnotinhibitedinanyofthe417fungalstrainstestedwhenexposedtolight.However,enhancedUV-Bradiationmayincrease,decrease,orleaveunaffectedtheseverityofbioticdiseases.Aseriouscomparisonofthiscontradictoryinformationisnotpossiblesince,intheunderlyingstudies,therangesoflightqualities,lightintensities,andlightexposuresweretoolargeandtoovariableasweretheexperimentaldesignsandtimecoursesapplied(ManningandvonTiedemann1995).
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Ifsomepartsofthediseaselifecyclearephotoperiodsensitive,populationsmightneedtoundergoextensiveadaptationtomakeuseofextendedseasonsintemperateareas(Garrettandothers2006).
UV-Bhaspositiveandnegativeeffectsonfungaldevelopment;itseffectondiseasesismainlythroughalteredphysiologyandmorphology(Chakrabortyandothers1998).
Air quality effects—Asnotedabove,increasedcarbondioxideintheatmosphereisgenerallycitedasbeingaprimaryfactorindrivingphysiologicalchangesinplantpopulations.Workingwithapasturelegumeandafungus(Coletotricumgloeosporioides)attwotimesambientcarbondioxideconcentration,Runion(2003)reportedanincreaseofvirulenceofthediseaseagainstresistantcultivarsofthelegume(nochangewithrespecttosusceptiblecultivars)andasignificantincreaseinfecundity(morepronouncedintheaggressivefungalcultivarsbeingtested).ChakrabortyandDatta(2003)focusedparticularconcernonwhetherthisincreasedfecundityatelevatedcarbon-dioxidelevelscouldrapidlyerodetheusefulnessofdiseaseresistance.Alteringthepredispositionofthehosttodiseasemaybethepredominanteffectofrisinglevelsofcarbondioxide(ManningandvonTiedemann1995).
Charkrabotoryandothers(1998)reportanincreaseofdiseaseseverityinresponsetoincreasedcarbondioxidefor6of10biotrophicfungiand9of15necrotrophicfungi;andobservethatpredictingeffectsforunstudiedpathosystemswillbechallenging,andevenmorechallengingwhenincludingthecombinedeffectsondiseasesandtheirhostplants.
Burdonandothers(2006)suggestthattheeffectofcarbondioxidemaybetoincreasetheefficiencyofcarbonfixationwitharesultantincreaseingrowthandimprovementinthecarbonstatusoftheplant.Thisincreasewouldleadtomorphologicalchangegenerallyexpressedasenhancedgrowth;thecombinedchangesinnutritionandmorphology,inturn,couldaffectthesuitabilityoftheplantashostmaterialforavarietyofdiseases.Thishavingbeensaid,theauthorscautionthatthereportedresearchonthesubjectislimitedandendthediscussionwiththisfurthercaution:“…thepredictabilityoftheimpactofthesefactorsasonwholecommunitiesisevenmoreuncertainwithbothindirectanddirecteffectsofvaryingmagnitudebeinglikely.”
MirroringthisconcernLemmenandWarren(2004)reportthatalthoughnumerousstudieshaveinvestigatedtheimpactsofelevatedcarbondioxideonforestgrowthandhealth,theresultsareneitherclearnorconclusive.
ManningandKeane(1988)concludethat“inatheoreticalsense,airpollutioncanincrease,decreaseornotaffectthe
courseofdevelopmentofadiseaseepidemic,”basedonnewandexistingobservationsaboutairpollutionandpestbehaviorincluding:
• Bacterialdiseasesaregenerallyinhibitedbysulfurdioxide,whichlimitslesionsizeandoftenincreaseslatentperiods.
• Fungaldiseaseshavebeenreportedtobeenhanced,inhibited,ornotaffectedatallbyairpollutants.
• Thelittlethatisknownabouttheeffectsofpollutiononrootdiseasesindicatesthatvirus-affectedplantsareusuallylessaffectedbyairpollutantsthanvirus-freeplants.
• AccordingtoJamesandothers(1980a),inoculatedstumpsofozone-stressedpines(Pinusspp.)weremorereadilyinvadedbyannosumrootdisease(causedbyHeterobasidionannosum).
• AccordingtoSkellyandothers(1983),ozonestressedeasternwhitepine(Pinusstrobus)intheBlueRidgeMountainsofVirginiaweremoresubjecttoLeptographiumrootdisease(causedbyVerticicladiellaprocera).
• AccordingtoMahoneyandothers(1985),loblollypineseedlingswithectomycorrhizae(Pisolithustinctorius)werenotadverselyaffectedbyozone,sulfurdioxide,oracombinationofboth.
• AccordingtoKeaneandManning(1987),ozonecausedsignificantdecreasesinectomycorrhizaeofwhitebirch(Betulapendula)andwhitepineseedlings.
Soil environment effects—Carbondioxideconcentrationinsoilisexpectedtobefarlessimpactingtodiseasesthanatmosphericcarbondioxide.Soilmicrofloraisroutinelyexposedtolevels10to20timeshigherthanatmosphericcarbondioxidelevels(Coakleyandothers1999;ManningandvonTiedemann1995).Colonizationandpersistenceofmycorrhizaeappearstobedependent,inpart,onthenutrientstatus(primarilynitrogen)andcarbondioxideconcentrationinsoil,althoughobservedresponsesdonotshowaconsistentpattern.Notmuchmorecanbesaidherebecausetheinfluenceofmycorrhizaeonplantdiseaseisstillnotwellunderstood.
Ozonedoesnotpenetratethesoilsurfaceandthereforeaffectsrootsonlyindirectlybyalteringphotosynthesis.Damagecausedbyseveraltreerootdiseasepathogensbecamemoreseverewhenthehostplantwasstressedbyozone(Fennandothers1990;Jamesandothers1980b,1982;Skellyandothers1983).
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O’Neill(1994)presentsadetailedreviewofthepotentialeffectsofelevatedlevelsofcarbondioxideontherhizosphere(theregionofsoilthatisdirectlyinfluencedbyrootsecretionsandassociatedsoilmicroorganisms),observingthatecosystemsarelargelyconstrainedbytheratesatwhichsoilprocessesoccur.Muchmoredatawillbeneededtobegintheprocessofgeneralizedmodelingofeffectsontherhizosphere.
Effectsofsoilsaturationhavealreadybeenbrieflydiscussedabove.Boththeamountofwaterandtimingoffloodingaffectthedegreeofnegativeimpactoncoverplants.
Soilcharacteristics,nutrientavailability,anddisturbanceregimesmayprovetobemoreimportantthantemperatureincontrollingfutureecosystemdynamics(LemmenandWarren2004).Climateandvegetationinteracttodeterminethecharacteristicsoilsofanarea,anddifferentclimaticzonesarecharacterizedbydifferentsoiltypes—exceptwherethepresenceofunusualrock,suchasserpentine,resultsinuniquesoils(MalcolmandPitelka2000).
effects on host Biology
Littleisknownabouthowenvironmentaleffectsontreephysiologyinfluencetheinducibleresponsesthatarerelevanttopathogens(signalrecognition,generationofphytoalexinsandreactiveoxygenspecies,hypersensitiveresponses,callusgrowth,andsystemicacquiredresistance)(AyresandLombardero2000).
Carbondioxideisaprimaryinputtogrowthanddevelopmentofallplantlife,providingbothafertilizationeffectandanincreaseintheefficiencywithwhichplantsusewater.Thefertilizationeffectmaybeaffectedbytheavailabilityofwaterandothernutrients.Itmayalsodiminishafteraninitialperiodofadjustmentbytheplant.Increasedcarbondioxidelevelsmayalsotriggerchangesinthechemicalcompositionofvegetationsuchasaffectingthecarbon-to-nitrogenratioinleaves(Winnett1998).Positiveresponsetocarbondioxideappearstooccurunderawiderangeofnutrientavailability(Rogersandothers1994).Inaddition,Bazzazandothers(1994)stressthatthedifferentialresponsesofspeciestoelevatedlevelsofcarbondioxideindicatepotentialshiftsinthecompetitiverelationshipsamongplants.Partialclosureoftheguardcellsformingstomateshasbeenproposedasthemechanismbywhichplantsslowtranspiration(JonesandMansfield1970),whichinturnmaybeonemechanismofadaptiveresistancetoelevatedcarbondioxidelevels.
Otherfactorstoconsiderincludethefollowing:
• Insoils,somefungicanusecarbondioxideasanadditionalsourceofcarbon,whichisincorporatedinto
organicacidsandeventuallyenterstheKrebscycleasanadditionalenergysupply(ManningandvonTiedemann1995);thisincreasetendstoincreaserootgrowthmorethanabovegroundgrowth(Rogersandothers1994).
• Ozoneeffectsonplantdiseasesarehostmediated.
• TheprincipalmechanismforUV-Beffectsonplantdiseaseswouldbethroughalterationofhostplants(ManningandvonTiedemann1995).
• Host-pathogenrelationships,defenseagainstphysicalstressors,andthecapacitytoovercomeresourceshortagescouldbeimpactedbyrisesincarbondioxide(Rogersandothers1994).
• Duringwinterdormancy,directeffectsofclimateonthehostaregenerallylessimportantthanthoseinvolvingapathogen(LonsdaleandGibbs1994).
combined effects
Increasedsummertemperaturesanddroughtinesswouldbeexpectedtohelpshiftthedistributionsoffunginorthwardswithintherangeofpotentialhosts,oratleasttoincreasethegeographicrangeoverwhichtheybehaveaspathogens(LonsdaleandGibbs1994).
Fungiappeartobelargelytolerantofcurrentozonelevels.However,astrongnegativecorrelationexistsbetweenrainfallorrelativeairhumidityandphotochemicalozonegenerationintheatmosphere:onwetdaysthatareappropriateforfungalgrowthonplantsurfaces,ozonelevelsareusuallylow.Consequently,biologicallyharmfulconcentrationsofozoneareunlikelytocoincidewithgerminatingsporesoractivelygrowingmycelium(ManningandvonTiedemann1995).
Expectedincreasesingrowthfromelevatedcarbondioxidelevelswillalmostcertainlyaggravateproblemswithdiseases.However,thiseffectwouldlikelybeoffsetbygrowthreductionscausedbyincreasedozoneandUV-B(ManningandvonTiedemann1995).Becausecarbondioxidemaygreatlyalterecosystemstructureandfunction(BazzazandFajer1992),unmanagedforestecosystemsmaybeseriouslyimpactedbycarbondioxideactingincombinationwithdrought,comparedtointensivelymanaged,monoculturetreefarmswherespeciescompositionhasbeenaltered.Overalltheinteractionofcarbondioxideandtemperatureisnotwellunderstoodandtheexperimentaldatahavebeeninconsistent(Rogersandothers1994).
Athighertemperatures,anincreaseintheavailabilityofallmajornutrients(nitrogen,phosphorus,calcium,magnesium,potassium,andsulfur)canbeexpectedasaresultof
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increasedwaterfluxesthroughsoilandhigherorganicmatterdecompositionrates,whichwouldincreasethecirculationofnutrientsinthesoil-nutritionsystem.Also,nutrientcirculationwouldincreasebecauseofhighergrowthratesofforestspeciesatincreasingatmosphericcarbondioxideconcentrationandwarmertemperature(Nilsonandothers1999).
Stressedtreesaremoresusceptibletoinsectpestsanddiseases(BroadmeadowandRay2005),enablingsomelevelofassessmentbyforestpathologistsandentomologists.However,firmprojectionsoffuturepestactivitycannotbemadeandconsiderablecautionshouldbeexercisedinextrapolatinganalysistoafutureclimate.Forsomeinsectsanddiseases,likelytrendscannotbepredictedevenonthebasisofexpertjudgment(BroadmeadowandRay2005).
Climatechangewilldirectlyinfluenceinfection,reproduction,dispersal,andsurvivalamongtheseasonsandothercriticalstagesinthelifecycleofadisease(CoakleyandScherm1996).Observedoutcomesincludemodificationsinhostresistance,alteredstagesandratesofdiseasedevelopment,andchangesinthephysiologyofhost-pathogeninteractions(Scherm2003).
eFFecTS oN ecoSySTemS
Becauseindividualspecieswillrespondtoclimatechangedifferently,ecosystemswillnotnecessarilyshiftascohesiveunits.Themostvulnerablespeciesareexpectedtobethosewithnarrowtemperaturetolerances,slowgrowthcharacteristics,andlimitingdispersalmechanismssuchasheavyseeds(LemmenandWarren2004).Howwellplantandanimalspeciesadapttoormovewithchangesintheirpotentialhabitatisstronglyinfluencedbothbytheirdispersalabilitiesandbythecharacteristicsandseverityofdisturbancestotheseenvironments.Nonnativeandinvasivespeciesthatdisperserapidlyarelikelytofindopportunitiesinnewlyformingcommunities(Joyceandothers2001).However,ifclimatechangecausesagradualshiftofcroppingregions,pathogenswillfollowtheirhosts(GoudriaanandZadocks1995)intolesschangednewcommunities.
Thepatternofdisturbanceimposedonalandscapebyaparticularbioticagentisdeterminedbothbythestructureandconditionofthelandscapeandbythecharacteristicsoftheagentanditsresponsivenesstoenvironmentalconditions(MamlstromandRaffa2000).Factorssuchaschangesinlanduseorincreasesinresistantstrainsofdiseasesmayunderlierangeexpansions(Harvellandothers2002).
Daleandothers(2001)pointoutthatmanydisturbancesarecascading.Forexample,insectinfestationsanddiseasespromoteforestfiresbycreatingfuels,andthefiresinturn
promotefutureinfestationsandinfectionsbycompromisingtheresistanceofsurvivingtreestoinsectsanddiseases.Invasivenonnativespeciesaresometimesabletomodifyexistingdisturbancesorintroduceentirelynewones.Underclimatechange,thesecompoundedinteractionsmaybeunprecedentedandunpredictable.Theyarelikelytoappearslowlyandbedifficulttodetectbecauseoftreelongevity.
Climatechangecouldrepresentanewformofdisturbancetounmanagedecosystemsandthuscouldprovidenewopportunitiesforinvasivespeciestoflourishanddisplacenativespecies.Animportantfeatureofmanyinvasivespeciesistheirdispersaleffectivenessandtheirhighreproductiverates(MalcolmandPitelka2000).Changesinphonologicalsynchronicityofhostsandnativepests,aswellastheirrelativeabundanceandphysiologicalcondition,mayaffectthefrequencyandconsequencesofoutbreaks(Malcolmandothers2006).
eFFecTS oN DiSTRiBuTioN oF SPecieS
Asclimateshifts,climaticallysensitivespecieswilleventuallydieout,andonlyasubsetofthepotentialpoolofincomingplantsmayactuallymigratesufficientlyquicklytokeepupwiththeshiftingclimate.Thus,plantcommunitiescouldbecomeprogressivelycomposedofthemoreadaptableandfastermovingspecies,especiallyifwarmingisrapid.Thischangeinplantcommunities,especiallytreecommunities,isofconsiderableconcern.Expansionofthewarm-temperaturemixed-evergreenforestsoftheSouthwouldbeattheexpenseofotherkindsofforests.Insomescenarios,partsoftheSouthbecomedrierandgrasslandsorsavannahsreplacethecurrentforest(MalcolmandPitelka2000).
TheforestareaimpactedbyinsectsanddiseasesintheUnitedStatesisapproximately45timesthatimpactedbyfire,withaneconomicimpactthatisalmost5timeslarger(Daleandothers2001).Ifthistrendcontinues,pestsanddiseasesarelikelytobetheprimarycauseofspecieschangeineasternforestsoverthenextfewdecades.Forecastingthetrajectoryofthosechangesisnearlyimpossiblebecausewecannotpredictwithanycertaintywhichpestsordiseaseswillbeestablished(Lovettandothers2006).Giventhecomplexitiesofclimatechange,andbioticresponsestoit,predictionofthefutureimpactofclimatechangeonemerginginfectiousdiseasesisdifficultexceptonabroadscale.Climatechangecanleadtotheemergenceofpreexistingpathogensasmajordiseaseagentsorcanprovidetheclimaticconditionsrequiredfornonnativediseasestoflourish(Andersonandothers2004).Becauseclimatechangewillallowplantsanddiseasestosurviveoutsidetheirhistoricranges,Harvellandothers(2002)haveprojectedanincreaseinthenumberofinvasivediseases.
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The following discussion and analysis is excerpted with only very minor changes from Régnière and Bentz (2008) and provides an example for consideration of a pest present and destructive in the western United States which and its potential impact in the East and South under the influence of climate change.
The mountain pine beetle (Dendroctonus ponderosae) is a native insect of pine forests in Western North America. Although it has a broad geographical distribution, it has been historically confined in the United States, by the distribution of its pine hosts, and in the northern half of British Columbia, by the geoclimatic barrier of the Rocky Mountains. Since the early to mid-1990s, an outbreak has reached unprecedented levels in terms of acreage and number of pine trees attacked. Lodgepole pine (Pinus contorta) is being killed throughout its range, most notably in Colorado and British Columbia. The beetle is also causing very high mortality among whitebark pine (Pinus albicaulis) and limber pine (Pinus flexilis) at high elevations. Historical records from the past century suggest that these ecosystems have had pulses of infestation and mortality but not at the levels currently being observed. Since 2006, the range of infestation has expanded into the Peace River area of north-central Alberta. Climate change may well be involved in this recent northeastward and upward range expansion. Evidence of similar shifts in insect distributions is ample and mounting throughout the world, much of it convincingly linked to climate change.
The primary concern at this time is the likelihood that the infestation will continue spreading eastward into the pines of the Canadian boreal forest, eventually reaching the eastern provinces and threatening the pines growing on the Atlantic side of the continent and then spreading into the Southern United States. Because of its recent incursion to the edges of the Canadian boreal forest, mountain pine beetle is viewed as a potential invading species in eastern pine ecosystems.
Three well-understood links connect climate and mountain pine beetles and form the basis for the concern that changing climate (temperature and precipitation) has had—and will continue to have—a role in the recent outbreaks and range expansion of this insect.
1. A well-synchronized adult emergence pattern is a prerequisite for successful mass attack of healthy pine trees. Such highly synchronized emergence is most likely to occur where (and when) the insect has a strictly univoltine (one generation per year) life cycle.
2. Cold winter temperature is the major cause of mortality in mountain pine beetles. For more than 20 years, process-based models describing responses to temperature have been under development; they show that a hemivoltine life cycle (one generation every 2 years) entails exposure to two winters, leading to lower population performance.
3. Drought affects the ability of pine trees to defend themselves against insect attack.
Three model components are available to study the impact of weather on mountain pine beetle populations: a phenology model that predicts life stage-specific developmental timing, a cold-tolerance model that predicts probability of larval mortality resulting from cold temperature, and a drought-stress model that predicts fluctuations of tree susceptibility. All three models have been implemented within BioSIM to make landscape-scale predictions of mountain pine beetle performance under climate change scenarios. BioSIM is a generic modelling tool that uses available knowledge about the responses of particular species (usually pests) to key climatic factors to predict their potential geographic range and performance.
The phenology model is very good at predicting the portions of the continent where the insect has a high likelihood of being univoltine. This model predicts the northward and upward shift of infestation. Under a conservative climate change scenario, it also predicts that by the end of the 21st century, the area at risk will shift considerably northward, to a point that the insect may be maladapted over much of its current distributional range. The cold tolerance model suggests that winter survival is very low and will remain so in the foreseeable future throughout the boreal pine forests from Alberta to Ontario. Although drought stress is, and is predicted to be, more common in that same area, there is not a very large change in this risk factor predicted in the near future.
Thus, with our current understanding of the insect’s physiology and host plant interactions, the risk of seeing the mountain pine beetle spread across the northern forests of Canada into the eastern pine forests seems rather low. This prediction, of course, is contingent on failure of the insect to adapt (evolve) and change its thermal responses, and on a relatively stable distribution of pines over the time range under consideration.
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Describingsimilareffectsforpestinsectsinclimatechangescenarios,Loganandothers(2003)indicatethatthereisahistorictrendtointensificationinallaspectsofoutbreakbehavior,basedonassessmentsofindividualspecies’responsestodate;thiscertainlycharacterizesmodelingworkwiththemountainpinebeetle(Dendroctonusponderosae),gypsymoth,sprucebeetle(Dendroctonusrufipennis),andsprucebudworm(Choristoneurafumiferana).
Waltherandothers(2002)linkclimatechangetochangesinavarietyofknownspringtimelife-cycleeventsinEuropeanorganisms(includingearlierannualbirdbreeding,migrantbirdarrival,theappearanceofbutterflies,chorusesandspawningofamphibians,andshootgrowthandfloweringofplants);thesechangesineventtimingsuggestalengtheningofgrowingseasonby8to16days.Andersonandothers(2004),citinggreyleafspot(Pyriculariagrisea)diseaseofcorn(Zeaspp.),suggestthattherangesofseveralimportantcropinsects,nonnativeplants,andplantdiseaseshavealreadyexpandednorthward.Theyalsonotethatautumnlife-cycleevents(leafcolorchangeandleaffall)arenotasclearlydefinedintheirresponsetotheextensionofgrowingseasonasspringtimeevents.
Plantshavehistoricallyrespondedtoclimatechangebymigrationandadaptation.Fragmentationandrateofseedlingestablishmentmayhindersomeplantpopulationsfromsuccessfulmigrationtohigherlatitudes.Persistenceofthesepopulationsmaydependheavilyonadaptiveevolution,butpredictedratesofevolutionaryresponsearemuchslowerthanthepredictedrateofclimatechange.Historicalclimatechangesweregenerallymuchslower(byoneormoreordersofmagnitude)thanthosepredictedforthefuture(EttersonandShaw2001).Thisobservationleadstoconcernthathistoricalresponsepatternstoclimatechangemaynotprovetobeeffectiveaspredictorsoffuturechange.
Addingtotheconcernsexpressedaboveisacriticalconsiderationthathasnotyetbeenemphasizedenough—climatechangecannotbeviewedinisolation;itseffectsonecosystemsmustbeconsideredinthecontextofarangeofhuman-causedimpactsonecosystems,suchasairpollution,waterpollution,habitatdestructionandfragmentation,andthenonnativespeciesthatthriveandhavetheirmostseriouseffectsinecosystemsalreadydisturbedbyhumanactivities(MalcolmandPitelka2000).
Manyunpredictable,unforeseenpestproblemsmayariseasaresultofchangingtemperatures,changingprecipitationregimes,orbothincombination.Previouslyminororinfrequentpestsmaybecomesignificantcausesoftreemortality.Somecurrentmajorpestsmaydeclineinimportance.Inadditiontonewnonnativeinvasivepestsarrivingfromoverseas,therangesofinsectsanddiseasesnativetoNorthAmericamayexpandor
contractdramatically.Becausethesechangesarelargelyunpredictableyetboundtooccur,landmanagersandscientistsinforestry-relateddisciplineswillneedtopracticeearlydetectionandmonitoringof“new”problemsandfollowupwithresearchandcreative,adaptivemanagementstrategies.
PAThoSySTemS
Thesubtlechangesinconditionsattributedtoclimatechangecanaffectplant-diseasedevelopment.Thesechangesarenoteasilydetermined,and,consequently,theabilitytoforecasthowdiseasechangesunderalteredgrowthconditionsisnotsimple(Seem2004).
Lessstablerelationshipstendtooccurinthesimplerecosystemsthatinitiallyexistinplantedforests,ofteninvolvingnewcombinationsofhostandpathogenspeciesthathavebeentransportedbeyondtheirnaturalgeographicranges.Insuchsituations,climatechangewouldlikelyencouragemajorchangesindiseaseincidenceandseverity(LonsdaleandGibbs1994).
Tree-diseaseproblemscannotbefullyunderstoodwithoutathoroughappreciationofthepartplayedbyenvironmentalfactors,particularlyclimate,asaprecursortofungalattack.Themanifestationofmanydiseasesoftenmerelyreflectsunfavorablesitefactors,thepresenceofthefungusbeingtheresultofanunhealthyconditionratherthantheprimarycauseofthetree’sdebility(Gilmour1960).
Duringunusualweathereventsorbiologicallyinducedstressperiods,thecompetitivedominantmaybethemostvulnerable.Itslargesizehasstretcheditslimitstocoordinateuptake,transport,storage,andphotosynthesis(ManionandLachance1992).
Thetimingofthestresseventisalsoveryimportant.Earlyseasonstressisfrequentlyovercomealthoughlaterstressorsarenotso,oftensimplybecauseofsufficienttimeremaininginthegrowingseason(LundquistandHamelin2005).
NonnativeinsectpestsanddiseasesposethemostseriousthreattotheforestsofeasternNorthAmerica.Thelitanyofpestanddiseaseintroductionsislong:chestnutblight(Cryphonectriaparasitica),Dutchelmdisease(Ophiostomaulmi),beechbarkdisease(Nectriacoccineavar.faginata),balsamwoollyadelgid(Adelgespiceae),hemlockwoollyadelgid(A.tsugae),dogwoodanthracnose(Disculadestructiva),andgypsymoth(Lovettandothers2006).
AccordingtoLovettandothers(2006),ecologistsneedadequateinformationinonlysixcategoriesofknowledgeaboutnonnativepestsandtheirhoststomakeroughpredictionsofthetypeandmagnitudeofpotentialecosystem
504The Southern Forest Futures Project
impacts.Pestinformationisneededconcerning:(1)modeofaction,(2)hostspecificity—suchasspeciesandageclass,and(3)virulence.Withrespecttothehost,theinformationneededis:(4)ecologicalimportance—positionorbio-productionvaluesinthesystem,(5)uniqueness,and(6)phytosociology—suchaspureversusmixedstands,effectivenessofregeneration.
Whenclimatechangehasasignificantanddirecteffectonplants,changesincompositionmayensue.Givendifferentialresponsesacrossplantspecies,thismayleadtorelativechangesincommunitycomposition.Whencoupledwithrangeextensionsorcontractionsofindividualspecies,theresultmaybeincreasedordecreaseddiversityofwholeplantcommunities.Diseasesofonehostspeciesmaythusbebroughtintointimatecontactwithnewhosts,althoughthelikelihoodofspatialmovementsnecessaryforthistooccurisperhapslowintheimmediatefuture;theymaybenefitfromincreasingoverlapofobligatealternatehostdistributions;ortheymaysuffersignificantreductionsinpopulationsizeasaconsequenceofallopatricdistributionsorincompletecongruenceinthedistributionofobligatealternatehosts(Burdonandothers2006).
Bolandandothers(2004)summarizeresearchonthepotentialimpactofclimatechangeonplantdiseasesandlist143plantdiseases,only18ofwhichareforesttreediseases.Despitethistheytabulatedataforclimatechangeeffectswithrespecttoforestpathosystemsunderthesecategories:primaryinoculumordiseaseestablishment,rateofdiseaseprogress,potentialdurationofepidemic,reasonsforeffects,andneteffectofthedisease.Althoughpredictingtheeffectsonthediseasesisrelativelyintuitivetoplantpathologists,theauthorsarguethatextendingtheintuitiveknowledgepathosystemsordiseasemechanismsrequiresmoreknowledgeabouthowthehost’sphysiologyandthusthehost-pathogeninteractionwillbeaffected.Theyalsociteaspecificneedforfurtherknowledgeabouttheeffectsofelevatedcarbondioxide,UVradiation,andgroundlevelozone,aswellastheeffectsofenvironmentalchangesoninsectvectorsofdiseases.
Aninterestingsidebartopathosystemsactivityisreflectedinthecapacityoffungitoperformtheircleanupfunction(woodyandleaflitterdecomposition)undertheinfluenceofclimatechange.Yin(1999)makesseveralpoints.First,thedecayrateofforestwoodydebrisisakeymissinglinkinourquantitativeunderstandingofcarbondynamicsandtheglobalcarbonbudgetofforests.And,inthecontextofglobalclimatechange,a2°CwarminginairtemperatureinJanuaryandJulywouldacceleratestemwoodydebrisdecay(indensityloss);accelerateddecaywoulddecreaseinthepresenceofincreasedprecipitation(andvice-versa);but,themagnitudeofincreasewouldbesmallerwhenadjustedforthedetrimentaleffectofelevatedcarbondioxideaspartofclimatechange.
Formanyfungaldiseasesthatrelyonbioticvectorsfordispersal,theeffectsofclimatechangeandweatheronthedevelopmentofoutbreaksorepidemicshavenotbeenstudiedindetail.Inareaswhereapathogenalreadyoccurs,weatherconditionsmayfavoroutbreaksofitsvectorsincertainyears,suggestingthatclimatechangecouldinfluencelong-termprevalenceofthedisease(LonsdaleandGibbs1994).Theintroductionofnewvectorspecies,changesinvectoroverwinteringandoversummering(Garrettandothers2006),andothereffectsofchangeoninsectsmayhaveimportanteffectsonpathogensurvival,movement,andreproduction(Garrettandothers2006).Pathogensthatrelyonvectorsmayseesignificantshiftsintheirdistributionorintensityifenvironmentalchangesaffectthebehaviororviabilityoftheirvector(Burdonandothers2006).
However,insomecircumstances,warmertemperaturescouldactuallyinhibitinsectactivityordisruptthebuild-upofpopulations.Enemiesofinsectpestswillalsobeaffectedbyclimatechange,buttheseeffectsareunknownandrequiremoreresearch.Ifwarmertemperaturespositivelyaffectpredatorsandparasitoids,naturalenemieswillexhibitgreatercontrolofpestspecies.Conversely,ifwarmertemperaturesdisruptordecreasepredatorandparasitoidpopulations,pestpopulationswillgrowmorequicklyandwillpersistathigherlevelsforlongerperiods.
liTeRATuRe ciTeDAnderson,P.K.;Cunningham,A.A.;Patel,N.G.[andothers].2004.Emerginginfectiousdiseasesofplants:pathogen,pollution,climatechangeandagrotechnologydrivers.TrendsinEcologyandEvolution19(10):535–544.
Ayres,M.P.;Lombardero,M.J.2000.Assessingtheconsequencesofglobalchangeforforestdisturbancefromherbivoresandpathogens.ScienceofTotalEnvironment262:263–286.(also:http://www.dartmouth.edu/~mpayres/pubs/gepidem.PDF).
Bazzaz,F.A.;Fajer,E.D.1992.PlantlifeinaCO2-richworld.ScientificAmerican266:68-74.
Beukema,S.J.;Robinson,D.C.E.;Greig,L.A.2007.Forests,insects&pathogensandclimatechange:workshopreport.Prineville,OR:TheWesternWildlandsEnvironmentalThreatAssessmentCenter.20p.(accessat:http://www.essa.com/documents/Forests,%20Pests%20and%20Climate%20-%20Workshop%20Report.pdf).
Black,B.A.;Shaw,D.C.;Stone,J.K.2010.ImpactsofSwissneedlecastonoverstoryDouglas-firforestsofthewesternOregonCoastRange.Webpublishedm.s.Corvalis,OR:OregonStateUniversity.35p.(accessathttp://ir.library.oregonstate.edu/jspui/bitstream/1957/15212/1/Black_et_al_FEM_SNC_study_2010%5B1%5D.pdf).
Boland,G.J.;Melzer,M.S.;Hopkin,A.[andothers].2004.ClimatechangeandplantdiseasesinOntario.CanadianJournalofPlantPathology26:335–350.
Brasier,C.M.;Scott,J.K.1994.Europeanoakdeclinesandglobalwarming:atheoreticalassessmentwithspecialreferencetotheactivityofPhytophthoracinnamomi.Bulletin-OEPP24(1):221–232.
Breshears,D.D.;Cobb,N.S.;Rich,P.M.[andothers].2005.Regionalvegetationdie-offinresponsetoglobal-changetypedrought.ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica102:15144–15148.
505chAPTeR 16. Invasive Pests—Insects and Diseases
Broadmeadow,M.;Ray,D.2005.ClimatechangeandBritishwoodland.InformationNote69.Edinburgh,UnitedKingdom:ForestryCommission.(also:http://www.forestresearch.gov.uk/pdf/fcin069.pdf/$FILE/fcin069.pdf).
Burdon,J.J.;Thrall,P.H.;Ericson,L.2006.Thecurrentandfuturedynamicsofdiseaseinplantcommunities.AnnualReviewofPhytopathology44:19–39.
Chakraborty,S.;Datta,S.2003.HowwillplantpathogensadapttohostplantresistanceatelevatedCO2underachangingclimate?NewPhytologist159:733–742.
Chakraborty,S.;Murray,G.M.;Magarey,P.A.[andothers].1998.PotentialimpactofclimatechangeonplantdiseasesofeconomicsignificancetoAustralia.AustralasianPlantPathology27:15–35.
Coakley,S.M.1988.Variationinclimateandpredictionofdiseaseinplants,AnnualReviewofPhytopathology26:163-181.
Coakley,S.M.;Scherm,H.;Chakraborty,S.1999.Climatechangeandplantdiseasemanagement.AnnualReviewofPhytopathology37:399–426.
Dale,V.H.;Joyce,L.A.;McNulty,S.[andothers].2001.Climatechangeandforestdisturbances.BioScience51:723–734.(also:http://www.usgcrp.gov/usgcrp/Library/nationalassessment/forests/bioone2.pdf).
Etterson,J.R.;Shaw,R.G.2001.Constrainttoadaptiveevolutioninresponsetoglobalwarming.Science294:151-154.
Fenn,M.E.Dunn,P.H.;Durall,D.M.1989.Effectsofozoneandsulfurdioxideonphyllospherefungifromthreetreespecies.AppliedEnvironmentalMicrobiology55:412-418.
Garrett,K.A.;Dendy,S.P.;Frank,E.E.[andothers].2006.Climatechangeeffectsonplantdisease:genomestoecosystems.AnnualReviewofPhytopathology44:489–509.
Gilmour,J.W.1960.Theimportanceofclimaticfactorsinforestmycology.NewZealandJournalofForestry8:250-260.
Goudriaan,J.;Zadocks,J.C.1995.Globalclimatechange:modelingthepotentialresponsesofagrosystemswithspecialreferencetocropprotection.EnvironmentalPollution87:215-224.
Hansen,A.J.;Neilson,R.P.;Dale,V.H.[andothers].2001.Globalchangeinforests:responsesofspecies,communitiesandbiomes.BioScience.51:765–779.
Harvell,C.D.;Mitchell,C.E.;Ward,J.R.[andothers].2002.Climatewarminganddiseaserisksforterrestrialandmarinebiota.Science.296:2158–2162.
Hepting,G.H.1963.Climateandforestdiseases.AnnualReviewofPhytopathology.1:31–50.
Humphrey,H.B.1941.Climateandplantdiseases.YearbookofAgriculture1941.Washington,DC:U.S.DepartmentofAgriculture:499-502.
IntergovernmentalPanelonClimateChange.2001.Climatechange2001:synthesisreport.AcontributionofWorkingGroupsI,II,andIIItothethirdassessmentreportoftheIntegovernmentalPanelonClimateChange.In:Watson,R.T.andtheCoreWritingTeam,eds.CambridgeUniversityPress,Cambridge,UnitedKingdom,andNewYork:398pp.
IntergovernmentalPanelonClimateChange.2007.Summaryforpolicymakers.In:Solomon,S.;Qin,D.;Manning,M.;Chen,Z.;Marquis,M.;Averyt,K.B.;Tignor,M.;Miller,H.L.,eds.Climatechange2007:Thephysicalsciencebasis.ContributionofworkinggroupItothefourthassessmentreportoftheIntergovernmentalPanelonClimateChange.Cambridge,UnitedKingdomandNewYork:CambridgeUniversityPress.20p.(also:http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf.).
James,R.L.;Cobb,F.W.,Jr.;Miller,P.R.[andothers].1980a.EffectsofoxidantairpollutiononsusceptibilityofpinerotstoFomesannosus.Phytopathology70:560-563.
James,R.L.;Cobb,F.W.,Jr.;Wilcox,W.W.[andothers].1980b.EffectofphotochemicaloxidantinjuryofponderosaandJeffreypinesonsusceptibilityofsapwoodandfreshlycutstumpstoFomesannosus.Phytopathology70:704-708.
Jones,R.J.;Mansfield,T.A.1970.Increasesinthediffusionresistancesofleavesinacarbondioxide-enrichedatmosphere.JournalofExperimentalBotany21:951-958.
Joyce,L.;Aber,J.;McNulty,S.[andothers].2001.PotentialconsequencesofclimatevariabilityandchangefortheforestsoftheUnitedStates.In:NationalAssessmentSynthesisTeam,eds.ClimatechangeimpactsontheUnitedStates:thepotentialconsequencesofclimatevariabilityandchange.Cambridge,UnitedKingdom:CambridgeUniversityPress:489–522.(also:http://www.srs.fs.usda.gov/pubs/ja/ja_joyce001.pdf).
Keane,K.D.;Manning,W.J.1987.Effectsofozoneandsimulatedacidrainandozoneandsulfurdioxideonmycorrhizalformationinpaperbirchandwhitepine.In:Perry,R.etal.London,GreatBritain:SelperLtd.:608-613.
Kleijunas,J.T.;Geils,B.W.;Glaeser,J.M.[andothers].2009.ReviewofliteratureonclimatechangeandforestdiseasesofwesternNorthAmerica.Albany,CA:U.S.DepartmentofAgricultureForestService,PacificSouthwestResearchStation.54p.
Lemmen,D.S.;Warren,F.J.,eds.2004.Climatechangeimpactsandadaptation:aCanadianperspective.Ottawa,Ontario:NaturalResourcesCanada.174p.
Logan,J.A.;Régnière,J.;Powell,J.A.2003.Assessingtheimpactsofglobalwarmingonforestpestdynamics.FrontiersinEcologyandtheEnvironment.1:130–137.(also:http://www.usu.edu/beetle/documents/Loganet.al.2003.pdf.[accessedJuly13,2009]).
Loehle,C.1996.Dosimulationsprojectunrealisticdieback?JournalofForestry94:13-15.
Lonsdale,D.;Gibbs,J.N.1994.Effectsofclimatechangeinfungaldiseaseoftrees.In:Frankland,J.C.;Magan,N.;Gadd,G.M.,eds.Fungiandenvironmentchange:symposiumoftheBritishMycologicalSociety.Cambridge,UnitedKingdom:CambridgeUniversityPress:1–19.
Lovett,G.M.;Canham,C.D.;Arthur,M.A.[andothers].2006.ForestecosystemresponsestoexoticpestsandpathogensineasternNorthAmerica.BioScience56(5):395–403.
Lundquist,J.E.;Hamelin,R.C.,eds.2005.Forestpathology:fromgenestolandscapes.St.Paul,MN:AmericanPhytopathologicalSociety,APSPress.175p.
Mahoney,M.J.;Chevone,B.I.;Skelly,J.M.[andothers].1985.Influenceofmycorrhizaeonthegrowthofloblollypineseedlingsexposedtoozoneandsulfurdioxide.Phytopathology75:679-682.
Malcolm,J.R.;Liu,C.;Neilson,R.P.;Hansen,L.;Hannah,L.2006.Globalwarmingandextinctionsofendemicspeciesfrombiodiversityhotspots.Conserv.Biol.20:238-248.
Malcolm,J.R.;Pitelka,L.F.2000.Ecosystemsandglobalclimatechange:areviewofpotentialimpactsonU.S.terrestrialecosystemsandbiodiversity.47p.Accessedat:http://www.pewclimate.org/docUploads/env_ecosystems.pdf.(July13,2009).
Mamlstrom,C.M.;Raffa,K.F.2000.Bioticdisturbanceagentsintheborealforests:considerationsforvegetationchangemodels.GlobalChangeBiology6:35-48.
Manion,P.D.;Lachance,D.L.1992.Forestdeclineconcepts:anoverview.In:Manion,P.D.;Lachance,D.L.,eds.Forestdeclineconcepts.St.Paul,MN:APSPress:181–190.
Manning,W.J.;Keane,K.D.1988.Effectsofairpollutantsoninteractionsbetweenplants,insectsandpathogens.In:Heck,W.W.;Taylor,O.C.;Tingley,D.T.,eds.Assessmentofcroplossfromairpollutants.London,G.B.:Elsevier:365-386.
506The Southern Forest Futures Project
Manning,W.J.;vonTiedemann,A.1995.Climatechange:potentialeffectsofincreasedatmosphericcarbondioxide(CO2),ozone(O3),andultraviolet-B(UV-B)radiationonplantdiseases.EnvironmentalPollution88:219–245.
McNulty,S.G.;Aber,J.D.2001.UnitedStatesnationalclimatechangeassessmentonforestecosystems:anintroduction.BioScience51:720–723.(also:http://www.usgcrp.gov/usgcrp/Library/nationalassessment/forests/bioone1.pdf).
McNulty,S.G.;Boggs,J.L.2010.Aconceptualframework:redefiningforestsoil’scriticalacidloadsunderachangingclimate.EnvironmentalPollution30:1-6.(also:doi:10.1016.j.envpol.2009.11.028).
Millstein,J.A.1994.Propagationofmeasurementerrorsinpesticideapplicationcomputations.InternationalJournalofPestManagement40:159-165.
NationalAssessmentSynthesisTeam.2000.ClimatechangeimpactsontheUnitedStates:thepotentialconsequencesofclimatevariabilityandchange.Washington,DC:U.S.GlobalChangeResearchProgram.541p.
Nilson,A.;Kiviste,A.;Korjus,H.[andothers].1999.ImpactofrecentandfutureclimatechangeonEstonianforestryandadaptationtools.ClimateResearch.12:205–214.
O’Neill.E.G.1994.Responseofsoilbiotatoelevatedatmosphericcarbondioxide.PlantandSoil165:55-65.
Redmond,D.R.1955.Studiesinforestpathology.XV.Rootlets,mycorrhiza,andsoiltemperaturesinrelationtobirchdieback.CanadianJournalofBotany33:595-627.
Régnière,J.;Bentz,B.2008.Mountainpinebeetleandclimatechange.In:McManus,K.;Gottschalk,K.W.Proceedings:19thU.S.DepartmentofAgricultureInteragencyResearchForumonInvasiveSpecies,2008(Jan.8-11:Annapolis,MD)Gen.Tech.Rep.NRS-P-36.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NorthernResearchStation:63-64.(Availableat:http://www.nrs.fs.fed.us/pubs/gtr/gtr_nrs-p-36.pdf).
Rogers,H.H.;Runion,G.B.;Krupa,S.V.1994.PlantresponsestoatmosphericCO2enrichmentwithemphasisonrootsandtherhizosphere.EnvironmentalPollution83:155-189.
Runion,G.B.2003.Climatechangeandplantpathosystems—futurediseasepreventionstartshere.NewPhytologist159:531–538.
Scherm,H.2000.Simulatinguncertaintyinclimate-pestmodelswithfuzzynumbers.EnvironmentalPollution108:373-379.
Scherm,H.2003.Plantpathogensinachangingworld.AustralianPlantPathology32:157-165.
Scherm,H.;Coakley,S.M.2003Plantpathogensinachangingworld.AustralianPlantPathology32:157-165.
Seem,R.C.2004.Forecastingplantdiseaseinachangingclimate:aquestionofscale.CanadianJournalPlantPathology26:274-283.
Skelly,J.M.;Yang,Y.S.;Chevione,B.I.[andothers].1983.OzoneconcentrationsandtheirinfluenceonforestspeciesintheBlueRidgeMountainsofVirginia.In:Davis,D.D.;Millen,A.A.;Dochinger,L.S.,eds.Airpollutionandtheproductivityofforests(Oct.4-5,1983:Washington,DC).StateCollege,PA:PennsylvaniaStateUniversity,IsaacWaltonLeagueofAmerica.344p.
Sturrock,R.N.2007.Climatechangeeffectsonforestdiseases:anoverview.In:Jackson,M.B.(compiler).Proceedingsofthe54thannualWesternInternationalForestDiseaseWorkConference(Oct.2-6,2006:Smithers,BritishColumbia,Canada).Missoula,MT:USDepartmentofAgriculture,ForestService:51–55.
Walther,G.R.;Post,E.;Convey,P.[andothers].2002.Ecologicalresponsestorecentclimatechange.Nature.416:389–395.
Wigley,T.M.L.1999.Thescienceofclimatechange:globalandU.S.perspectives.Arlington,VA:PewCenteronGlobalClimateChange.http://www.pewclimate.org/docUploads/env_science.pdf.(July13,2009).
Winnett,S.M.1998.PotentialeffectsofclimatechangeonU.S.forests:areview.ClimateResearch11:39–49.(also:http://www.int-res.com/articles/cr/11/c011p039.pdf).
Yang,X.B.;Scherm,H.1997.ElNinoandinfectiousdisease.Science.275:739.
Yarwood,C.E.1959.Microclimateandinfection.In:PlantPathol.Probl.AndProgr.1908-1958.MadisonWI:Univ.Wisc.Press:548-556.
Yin,X.1999.Thedecayofforestwoodydebris:numericalmodelingandimplicationsbasedonsome300datacasesfromNorthAmerica.Oecologia.121:81–98.
oTheR ReFeReNceS
Annosum Root Disease
Anderson,R.L.;Mistretta,P.A.1982.Managementstrategiesforreducinglossescausedbyfusiformrust,annosusrootrot,andlittleleafdisease.Agric.Handbk.597.Washington,DC:U.S.DepartmentofAgriculture,ForestService.30p.
Asian longhorned Beetle
U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.2010.Planthealth:asianlonghornedbeetle.Washington,DC:U.S.DepartmentofAgriculture,AnimalandPlantHealthInspectionService.Webaccessedwww.aphis.usda.gov/plant_health/plant_pest_info/asian_lhb/index.shtml
U.S.DepartmentofAgriculture,ForestService.Foresthealthprotection–Asianlonghornedbeetle.Portalpage.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NortheasternArea,StateandPrivateForestry,ForestHealthProtection.Webaccessedatwww.na.fs.fed.us/fhp/alb/
Baldcypress leafroller
http://www.insectimages.org/browse/subthumb.cfm?sub=4300&Start=1&display=30&sort=2
http://www.fs.fed.us/r8/foresthealth/publications/patterns_of_defoliation_in_southeastern_louisiana_swamps.pdf
Balsam Woolly Adelgid
Ragenovich,I.R.;Mitchell,R.G.2006.Balsamwoollyadelgid.ForestInsect&DiseaseLeaflet118.Portland,OR:U.S.DepartmentofAgriculture,ForestService.12p.Availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-118.pdf).
Bark Beetle (see below for southern pine beetle)Ciesla,W.M.1973.Six-spinedengraverbeetle.ForestPestLeaflet141.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl141.pdf).
Clarke,S.R.;Evans,R.E.;Billings,R.F.2000.InfluenceofpinebarkbeetlesonthewestGulfCoastalPlain.TexasJournalofScience52(4)Supplement:105-126.
Beech Bark Disease
Brown Spot Needle Blight
Phelps,W.R.;Kais,A.G.;Nicholls,T.H.1978.Brownspotneedleblightofpines.ForestInsect&DiseaseLeaflet44.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-44.pdf).
507chAPTeR 16. Invasive Pests—Insects and Diseases
Butternut canker
Fleguel,V.R..1996.Aliteraturereviewofbutternutandthebutternutcanker.Inform.Rep.20.Ontario,Canada:MinistryofNaturalResources,EasternOntarioModelForest.32p.
Nicholls,T.H.1979.Butternutcanker.In:Proceedingsofthesymposiumonwalnutinsectsanddiseases.Gen.Tech.Rep.NC–52.St.Paul,MN:U.S.DepartmentofAgricultureForestService,NorthCentralForestExperimentStation:73–82.
Ostry,M.E.;Mielke,M.E.;Anderson,R.L.1996.Howtoidentifybutternutcankerandpreservebutternut.St.Paul,MN:U.S.DepartmentofAgricultureForestService,NorthCentralForestExperimentStation.4p.
Ostry,M.;Mielke,M.;Skilling,D.1994.Butternut—strategiesformanagingathreatenedtree.Gen.Tech.Rep.NC–165.St.Paul,MN:U.S.DepartmentofAgricultureForestService,NorthCentralForestExperimentStation.7p.
Dogwood Anthracnose
Anderson,R.L.;Knighten,J.L.;Windham,M.[andothers].1994.DogwoodanthracnoseanditsspreadintheSouth.Protect.Rep.R8–PR–26.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,State&PrivateForestry,ForestPestManagement.10p.
Britton,K.O.;Roncadori,R.W.;Hendrix,F.F.1993.IsolationofDisculadestructivaandotherfungifromseedsofdogwoodtrees.PlantDisease.77:1026–1028.
Daughtrey,M.L.;Hibben,C.R.;Britton,K.O.;Windham,M.T.;Redlin,S.C.1996.Dogwoodanthracnose:understandingadiseasenewtoNorthAmerica.PlantDisease.80:349–358.
Daughtrey,M.L.;Hibben,C.R.;Hudler,G.W.1988.CauseandcontrolofdogwoodanthracnoseinNortheasternUnitedStates.JournalofArboriculture.14(6):159–164.
Windham,M.T.;Graham,E.T.;Witte,W.T.[andothers].1998.Cornusflorida“AppalachianSpring”:awhitefloweringdogwoodresistanttodogwoodanthracnose.HorticulturalScience.33:1265–1267.
emerald Ash Borer
Various.2010.EmeraldAshBorerInformationNetwork.Lansing,MI:MichiganStateUniversity.Availableat:http://www.emeraldashborer.info.
U.S.DepartmentofAgriculture,ForestService.Foresthealthprotection–Emeraldashborer.Portalpage.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NortheasternArea,StateandPrivateForestry,ForestHealthProtection.Webaccessedathttp://na.fs.fed.us/fhp/eab/)
Forest Tent caterpillar
Harper,J.D.;Abrahamson,L.P.1979.ForesttentcaterpillarcontrolwithaeriallyappliedformulationsofBacillusthuringiensisanddimilin.JournalofEconomicEntomology.72:74–77.
Fusiform Rust
Anderson,R.L.;Mistretta,P.A.1982.Managementstrategiesforreducinglossescausedbyfusiformrust,annosusrootrot,andlittleleafdisease.Agric.Handbk.597.Washington,DC:U.S.DepartmentofAgricultureForestService.30p.
Dinus,R.J.;Schmidt,R.A.1977.Managementoffusiformrustinsouthernpines.In:Proceedingsofasymposium.Gainesville,FL:UniversityofFlorida.163p.
Matthews,F.R.;Anderson,R.L.1979.Howtosaveyourfusiformrustinfectedpinesbyremovingcankers.Bull.SA–FB/P7.Atlanta:U.S.DepartmentofAgricultureForestService,SouthernRegion,StateandPrivateForestry,ForestInsectandDiseaseManagement.6p.
Phelps,R.W.;Czabator.1978.Fusiformrustofsouthernpines.ForestInsect&DiseaseLeaflet26.Washington,DC:U.S.DepartmentofAgricultureForestService.7p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-26.pdf).
Schmidt,R.A.1998.Fusiformrustdiseaseofsouthernpines:biology,ecology,andmanagement.Tech.Bull.903.Gainesville,FL:UniversityofFlorida.14p.
U.S.DepartmentofAgriculture,ForestService(USDAFS).1971.Thinningpineplantationsin1971andafter.UnnumberedForestManagementBulletin.Atlanta:U.S.DepartmentofAgricultureForestService,SoutheasternArea,StateandPrivateForestry,ForestInsectandDiseaseManagement.6p.
Gypsy moth
Elkinton,J.S.;Liebhold,A.M.1990.PopulationdynamicsofgypsymothinNorthAmerica.AnnualReviewofEntomology.35:571–596.
Gottschalk,K.1993.Silviculturalguidelinesforforeststandsthreatenedbythegypsymoth.Gen.Tech.Rep.GTRNE-171.Radnor,PA:U.S.DepartmentofAgricultureForestService,NortheasternForestExperimentStation.49p.
McManus,M.;Schneeberger,N.;Reardon,R.;Mason,G.1989.Gypsymoth.ForestInsect&DiseaseLeaflet162.Washington,DC:U.S.DepartmentofAgricultureForestService.14p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-162.pdf).
U.S.DepartmentofAgriculture,ForestServiceandAnimalandPlantHealthInspectionService(USDAFSandothers).1995.GypsymothmanagementintheUnitedStates:acooperativeapproach.[UnnumberedRep.].Washington,DC:U.S.DepartmentofAgricultureForestService.Various[total1092p.]
hardwood Borer
Donley,D.E.;Accivatti,R.E.1980.Redoakborer.ForestInsect&DiseaseLeaflet163.Portland,OR:U.S.DepartmentofAgricultureForestService.7p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-163.pdf).
Graham,S.A.1959.Controlofinsectsthroughsilviculturalpractices.JournalofForestry.57:281–283.
Hay,C.J.;Morris,R.C.1970.Carpenterworm.ForestPestLeaflet64.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-64.pdf).
hemlock Woolly Adelgid
U.S.DepartmentofAgriculture,ForestService(USDAFS).2005.Hemlockwoollyadelgid.PestAlertNA-PR-09-05.NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NorhteasternArea,State&PrivateForestry.2p.(Also::http://na.fs.fed.us/spfo/pubs/pest_al/hemlock/hwa05.htm).
U.S.DepartmentofAgriculture,ForestService(USDAFS).2010.Hemlockwoollyadelgid[homepage].NewtownSquare,PA:U.S.DepartmentofAgricultureForestService,NortheasternArea.Variousp.[http://na.fs.fed.us/fhp/hwa/].
littleleaf Disease
Anderson,R.L.;Mistretta,P.A.1982.Managementstrategiesforreducinglossescausedbyfusiformrust,annosusrootrot,andlittleleafdisease.Agric.Handbk.597.Washington,DC:U.S.DepartmentofAgricultureForestService.30p.
508The Southern Forest Futures Project
Mistretta,P.1984.Littleleafdisease.ForestInsect&DiseaseLeaflet20.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-20.pdf).
Nantucket Pine Tip moth
Berisford,C.W.1974.Comparisonsofadultemergenceperiodsandgenerationsofthepinetipmoths,RhyacioniafrustranaandR.rigidana.AnnalsoftheEntomologicalSocietyofAmerica.67:666–668.
Berisford,C.W.;Kulman,H.M.1967.InfestationrateanddamagebytheNantucketpinetipmothinsixloblollypinestandcategories.ForestScience.13:428–438.
Eikenbary,R.D.;Fox,R.C.1965.TheparasitesoftheNantucketpinetipmothinSouthCarolina.Tech.Bull.1017.Clemson,SC:SouthCarolinaAgriculturalExperimentStation.9p.
Eikenbary,R.D.;Fox,R.C.1968.ArthropodpredatorsoftheNantucketpinetipmothRhyacioniafrustrana.AnnalsoftheEntomologicalSocietyofAmerica.61:1218–1221.
Fettig,C.J.;Berisford,C.W.1999.NantucketpinetipmothphenologyineasternNorthCarolinaandVirginia:implicationsforeffectivetimingofinsecticideapplication.SouthernJournalofAppliedForestry.23:30–38.
Nowak,J.T.;Berisford,C.W.2000.Effectsofintensivemanagementpracticesoninsectinfestationlevelsandloblollypinegrowth.JournalofEconomicEntomology.93:336–341.
Warren,L.O.1985.PrimaryhymenopteransparasitesofNantucketpinetipmoth,Rhyacioniafrustrana(Comstock).JournalofEntomologicalScience.20:383–389.
Yates,H.O.,III;Overgard,N.A.;Koerber,T.W.1981.Nantucketpinetipmoth.ForestInsect&DiseaseLeaflet70.Washington,DC:U.S.DepartmentofAgricultureForestService.8p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-70.pdf).
oak Decline
Oak,S.W.;Courter,A.2000.Modelingoakdeclineeffectsonforestcompositionandstructurechangeusingtheforestvegetationsimulator[Abstract].In:Anon.Proceedingsofthefirstjointmeetingofthenortheastandsouthwideforestdiseaseworkshops.Morgantown,WV:WestVirginiaUniversity.[Notpaged].
Oak,S.W.;Huber,C.M.;Sheffield,R.M.1991.IncidenceandimpactofoakdeclineinwesternVirginia1986.Resour.Bull.SE–123.Asheville,NC:U.S.DepartmentofAgricultureForestService,SoutheasternForestExperimentStation.16p.
Oak,S.;Tainter,F.;Williams,J.;Starkey,D.1996.OakdeclineriskratingfortheSoutheasternUnitedStates.AnnalsdesSciencesForestiere.53:721–730.
oak Wilt
Appel,D.N.;Billings,R.F.,eds.1995.Oakwiltperspectives:Proceedingsofthenationaloakwiltsymposium.CollegeStation,TX:TexasForestService,TexasAgriculturalExperimentStation,TexasAgriculturalExtensionService.217p.
Pine Reproduction Weevil
Corneil,J.A.;Wilson,L.F.1980.Palesweevil—rationaleforitsinjuryandcontrol.MichiganChristmasTreeJournal.Fall:16–17.
Grosman,D.M.;Billings,R.F.;McCook,F.A.;Upton,W.W.1999.Influenceofharvestdateandsilviculturalpracticesontheabundanceandimpactofpinereproductionweevilsinwesterngulfpineplantations.In:Haywood,James,D.,ed.Proceedingsofthetenthbiennialsouthernsilviculturalresearchconference.Gen.Tech.Rep.SRS–30.Asheville,NC:U.S.DepartmentofAgricultureForestService,SouthernResearchStation:565–568.
Speers,C.F.1974.Palesandpitch-eatingweevils:developmentinrelationtotimepinesarecutintheSoutheast.Res.NoteSE–207.Asheville,NC:U.S.DepartmentofAgricultureForestService,SoutheasternForestExperimentStation.7p.
Stevens,R.E.1971.Pinereproductionweevil.ForestPestLeaflet15.Washington,DC:U.S.DepartmentofAgricultureForestService.6p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-15.pdf).
Southern Pine Beetle
Clarke,S.R.;Nowak,J.T.2009.Southernpinebeetle.ForestInsect&DiseaseLeaflet49.Portland,OR:U.S.DepartmentofAgricultureForestService.8p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-49.pdf).
Price,T.S.;Doggett,C.;Pye,J.M.;Smith,B.1998.AhistoryofsouthernpinebeetleoutbreaksintheSoutheasternUnitedStatesbythesoutheasternforestinsectworkinggroup.Macon,GA:GeorgiaForestryCommission.72p.
Swain,K.M.;Remion,M.C.1981.Directcontrolofthesouthernpinebeetle.Agric.Handbk.575.Washington,DC:U.S.DepartmentofAgriculture.15p.
Texas leaf cutting Ant
Bennett,W.H.1958.TheTexasleaf-cuttingant.ForestPestLeaflet23.Washington,DC:U.S.DepartmentofAgricultureForestService.4p.(availableathttp://www.fs.fed.us/r6/nr/fid/fidls/fidl-23.pdf).
[Grosman,D.]n.d.Leaf-cuttingant.Webpage.CollegeStation,TX:TexasForestService.(Availableat:http://txforestservice.tamu.edu/main/popup.aspx?id=1187(Accessed:Jun.28,2010.)
Cherret,J.M.1986.Historyoftheleaf-cuttingantproblem.In:Lofgren,C.S.;VanderMeer,R.K.,eds.Fireantsandleaf-cutting-antsbiologyandmanagement.Boulder,CO:WestviewPress:10–17.