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MAZINAIGANPAGE14FALL2013FORESTPESTSSometimeinthelate1800stinyinsectsarrivedontheeastcoastofNorthAmerica.ThebugsalmostcertainlyhitchedarideonnurserystockfromEurope.Nooneseemedtonoticethemuntil1908whenspecimensinBrunswickMainewereidentifiedbyascientistasthebalsamwoollyadelgid.In1931scientistsinNovaScotiastartedinvestigatinganabnormalityonbalsamfirbranchescallgoutdisease.Theyquicklyrealizedthisinsectwasthecauseandthatitwasbecom-ingabigproblemfortheareasbalsamfir.BythenthebalsamwoollyadelgidhadalreadyspreadacrossmostofNewHampshireVermontMaineNovaScotiaandPrinceEdwardIslandandintopartsofMassachusettsNewYorkandNewBrunswickaswell.TinyinsectcauseshugeproblemsforrtreesBySteveGarskeANAForestPestEnv.GrantCoordinatorMaturebalsamwoollyadelgids.Theadultsexcreteawhitecottonywaxthatprotectstheirbodiesandtheireggs.PhotobyRobertL.AndersonUSDAForestServiceBugwood.orgBWAdistributionintheUS.TheBWAisalsoestablishedinsoutheasternCanada.ProducedwiththeUSFSAlienPestExplorerhttpforesthealth.fs.usda.govportalFlexAPEDeadstandofmatureFraserrinNorthCarolina.SeedlingsandsaplingsaremoreresistanttotheBWAandcontinuetogrowforthetimebeing.PhotobyG.L.LenhardLouisianaStateUniversityBugwood.orgABWAcrawlerbeforeaccumulationofwhitewaxymaterial.Thisinsectislessthan132inchlong.AshvilleArchiveUSDAForestServiceBugwood.orgDamagetoFraserrneedles.PhotobyGreatSmokyMountainsNationalParkArchiveNPSBugwood.orgSwellinggoutingandneedlelosscausedbytheBWA.PhotobyDavidMcCombUSDAForestServiceBugwood.orgAround1955thebalsamwoollyadelgidBWAreachedtheisolatedhigh-elevationFraserfirstandsoftheAppalachianMountains.AlongwithredspruceFraserfiracloserelativeofbalsamfirwasadominanttreeonthesemountaintops.FraserfirhaslittleresistancetotheBWA.TheinsectspreadrapidlycarriedbythewindaswellasbypeoplemovingfirewoodlogsboughsnurseryplantsandChristmastrees.Over90ofthematureFraserfirtreesinthesestandshavenowbeenwipedout.TheBWAhasalsohitchedarideonnurserystockshippedtothePacificNorthwest.SomewesternfirspecieslikenoblefirarefairlyresistanttoBWAinfestationbutotherssuchassub-alpinefirarehighlysusceptible.Adelgidsaresimilartothefamiliaraphidsorplantlice.Bothadelgidsandaphidshavepiercingmouthpartsthataresortofshapedlikeastrawwhichtheyusetosiphonplantjuice.Thereareonlyabout50speciesofadelgidsintheworldallfoundinthenorthernhemisphere.Adelgidshavecomplicatedlifecyclesandchangeformsastheymature.Whileaphidsfeedonsugarsintheplantssapadelgidsfeedonstarchstoredintheplantscells.Aphidssecreteexcesssugarashoneydewwhileadelgidssecreteawaxysubstancethatcoverstheirbodiesandmakesthemlooklikespecksofwhitefuzz.LikemostotheraphidrelativesthelifecycleoftheBWAiscompli-cated.TostartwithonlyfemaleBWAsoccurinNorthAmerica.Thesefemalesareparthenogenicmeaningtheycanlayfertileeggswithoutmating.Astagecalledacrawlerhatchesfromtheeggs.Thesecrawlersarethesizeofpepperdots.Mostcrawlersstayclosetohomebutarelativehandfulmayhitcharideonabirdsfootorasquirrelsfirorarepassivelyblownonthewind.Thecrawlerssoonbeginfeedingandtransformintoaflatrest-ingstagewheretheywillremaintherestoftheirlives.TheBWAusuallyhastwogenerationsinthenorthanduptofourinthesouthernpartofitsrange.TheBWAoftenattacksthecanopyofthetree.Asitfeedsitinjectsahormonethatcausesthetwigstobecomeswollenatthebranchnodesandbelowthebudsandtheendsofthebranchestobecomestunted.Ifthetreesurvivesforseveralyearstheterminalstembeginstogrowatanangleinsteadofstraightupgivingthetreeafiddleheadappearance.Thetopdiesbackallowingfungitoinvadethetree.Thetreesneedlesstarttoturnyellowandfalloff.Coneandseedproductionisgreatlyreduced.Thetreedeclinesandeventuallydies.YoungfirtreesmakeachemicalcalledjuvabionethatgivesthemsomeresistancetotheBWAbutastheymaturetheymakelessofthischemicalleavingthemopentoattack.FirtreesarealsosusceptibletostemattackwherethetrunkbecomesheavilyinfestedwithBWA.PopulationsofBWAcanreach100-200persquareinchofbark.Stemfeedingcausesthetreetoproducedensebrittlewood.Thiswoodisnotasgoodattransportingwatertothecanopyofthetree.Itisalsomuchlessvaluableforlumberandpulp.InthesouthernAppalachianstreesthatareheavilystem-attackedoftendiewithinafewyears.Inthenortheaststem-attackedtreesusuallydiemoreslowlywithsomepersistingfor10yearsormore.TheBWAsspreadandimpactislimitedbycoldinthenorth.AstudyinNovaScotiafoundthatinareaswithaverageJanuarytemperaturesof12Fandbelowdamagetobalsamfirwasrelativelyminor.Anotherstudyfoundthattemperaturesof-30Forlowerfor24hourskilledalltheBWAsabovethesnowline.TheseconditionsroughlycorrespondtoUSDAZone4awhichincludesthewesternandcentralUpperPeninsulaofMichiganthenorthernthirdofWisconsinandthenorthernhalfofMinnesota.ThewarmingclimatewilllikelymovealltheseregionsexceptperhapsnortheastMinnesotaintozone4bwithinadecadeortwothough.TherestoftheGreatLakesregionisclassifiedaszone4borwarmerandwouldalreadysusceptibletoBWAdamageiftheinsectarrives.ThreebeetleandthreeflyspeciesfromtheBWAsnativerangehavesofarbeenintroducedtocombattheBWA.UnfortunatelythesebiocontrolinsectsStemattackonFraserr.Heavysteminfestationsoftenkillthetree.WilliamM.CieslaForestHealthMgmt.Intl.Bugwood.orgSeeValuedbalsamboughspage19