Introduction DiseaseManagementPreventionisthekeytodiseasemanagementinthehomegarden.Thereareseveraldiseasemanagementoptionsforthehomeapplegrowerthathaveminimalimpactonthegrowingenvironmentyethelptomaintainahealthycrop.Creatinganoptimalgrowingenvironmentforappleswillminimizeplantstress,whichinturnwillreduceplantdiseasesusceptibilityandultimatelyimprovecropyieldandtheaestheticsoftheplanting.

Severalsyntheticchemicalsandnaturalproducts(alsocalledbiopesticides)areavailabletoaidinthemanagementofplantdiseases,buttheyshouldalwaysbeusedinconjunctionwithculturalpracticesintendedtomodifytheenvironmenttomakeitlessconducivetodiseasedevelopment.

SiteSelectionandPreparation.Themostimportantmanagementdecisionisselectingwheretoplantyourappletrees.Pre-existingpathogens(fungi,bacteria,virus,andnematodes)caninfectnewtrees,causingreplantdisease(gradualtreedeclineandlackofvigor).Beforeplantingnewtreesintoasitepreviouslyplantedwithapples,removeasmanyoftheoldrootsaspossible.Somecrabapple,juniper,andcedarvarietiesareasourceofimportantfungithatcausediseaseinapples.Whenselectingalocationforyourappletreesconsiderplantingthetreesupwindofanycrabapple,juniperorcedartreesthatyoumayhaveinyouryard.

Chooseasunny(6to8hoursofsunlightperday),well-drainedlocationwithaslightsouthernfacingslope.Soilisthefoundationforhealthyandproductivetrees.Soiltemperature,moisture,pHandfertilityallinfluenceasoilpathogen’sabilitytosurviveandcolonizeplants.Appleswillgrowinawiderangeofsoiltypesbutgrowbestinsandyloam,loam,orsiltloamsoils.IdealsoilpHforapplesis6.0-7.0.HaveyoursoiltestedannuallytodeterminethepH,salts,nutrientsandorganicmatterlevels,andwaterholdingcapacity.

Thereisprobablynothingmorefrustratingforahomegardenerthantoseethefruitsofhisorherlaborslosttodiseasesandotherpests.Diseasesoccurwhenenvironmentalconditionsaresuitableforpathogenstoattackthehostplant.Somepathogensattackawidevarietyofplants,whereasothersattackonlyspecificplants.Additionally,somepathogenscanattackallplantparts,whereasothersattackonlyselectedtissues(i.e.flowers,fruit,rootsetc.).

Manytypesoforganismscauseinfectiousdiseasesofplants,butthefivemajorgroupsofplantpathogensarethefungi,watermolds,bacteria,virusesandnematodes.Adverseenvironmentalconditionsalsocancausedisease-likesymptomsonplants;referredtoasdisorders.TheseincludeimpropersoilpH,nutrientdeficienciesandtoxicities,soilcompaction,excesswater,herbicidedamageandmore.Plantsweakenedbyadverseenvironmentalconditionsmaybefurtherpredisposedtoattackbypathogens.

Successfuldiseasemanagementbeginswithaccurateidentificationofthecauseoftheproblem.Knowingthecommondiseasesofindividualcropsaidsgreatlyindiseaseidentificationandmanagement.Manydiseasesarereadilyidentifiedbasedoncharacteristicsigns(observationofthepathogenitself)andsymptoms(observationofdamagetotheplant)ofdisease.Theidentificationofotherdiseasesrequiresmicroscopicexaminationofdiseasedtissuesorevenmoresophisticatedlaboratorytechniques,whichareavailablethroughtheC.WayneEllett Plant&PestDiagnosticClinic,ColumbusOH.

PP Series No. 153

DEPARTMENT OF PLANT PATHOLOGY

VarietySelection.Inadditiontotheconsiderationofdwarfversusstandardvarieties,harvesttime,ortaste,diseaseresistancetoimportantdiseasesinOhioshouldbeconsidered.FourdiseasesthatcommonlyattackappletreesinOhioarefireblight,applescab,cedarapplerustandpowderymildew.Whileveryfewvarietieshaveresistancetoallfourdiseases,selectingvarietieswithresistancetoapplescab,whichisthemosttroublesomediseaseofappleinOhio,andfireblightisrecommended(seeTable1).Plantingdiseaseresistantvarietiescanreducetheneedforfungicideandbactericideapplications.

Pruning. Annualpruningofappletreesisnecessarytomaintaintreehealth,vigorandproductivity.Pruningpreventsthetreecanopyfromgettingtoodenseandpromotesgoodaircirculation,whichisveryimportantforpreventingmostdiseases.Wellprunedtreesarealsoeasiertospraywithpesticides.

Sanitation. Sanitationincludesvariousphysicalpracticesintendedtoreducepathogenpopulationsandpreventtheirspread.Manypathogenssurviveyeartoyearinthetree,onfallenleavesaroundthetreeandrottingfruit.Attheendoftheseasonremovediseasedfruitfromthetreeandground.Leavesandpruningdebrisshouldberakedandbagged.Diseasedbranchesshouldbeprunedandremovedduringthedormantseason.Diseasedplantmaterialshouldnotbecomposted.

SyntheticChemicals. Thehomegardenerhasseveraloptionsforchemicalcontrol.Mostoftheavailableproductsforhomegardenersworkoncontactandmustbeappliedbeforethediseaseoccursorassoonasdiseasesymptomsareobserved.Themostcommonfungicidesforhomegardenusecontainsulfur,copper,captan ormancozeb.Organicgardenerscanusesulfurorcoppertomanageapplediseases.Beforeapplyingapesticide,alwaysreadtheproductlabelcarefully.AlistofsyntheticchemicalsavailableforhomeownersisprovidedinTable2.Beforeapplyingafungicidealwaysreadtheproductlabelcarefully.

Biopesticides. Manyhomegardenersprefertouseorganicproductsthataremore“environmentallyorearthfriendly”thantraditionalsyntheticchemicals.Biopesticides arederivedfromnaturalmaterialssuchasplants,animals,minerals,andfungiorbacteria,andaremosteffectivewhenusedinconjunctionwith

Disease Management Home Apple Plantings -page 2

Resistance To

Variety AS CR FB PM Other Traits

CrimsonCrisp VR M

R S S red,harvestmid-September

Dayton VR R MR Rbrightmediumred,harvestmid-August,goodforsouthernOhioclimate

Enterprise VR VR MR Rlighttomediumred,mid-October,goodforsouthernOhioclimate

Freedom VR R VR R brightred,harvestlateSeptember

GoldenDelicious S S S VS yellow,harvestlate

September

GoldRush VR S MR Sdeepyellowwithredblush,harvestmid-October,goodforsouthernOhioclimate

Jonafree VR S S Rredstripes,harvestearlySeptember,goodforsouthernOhioclimate

Liberty VR R R R redstripesongreenyellow,harvestlateAugust

Macfree VR VR MR Smediumredovergreenyellow,harvestmid-September

NovaEasygro VR VR R S

80%darkredongreenyellow,harvestearlySeptember

PixieCrunch VR — — — Deepred,harvestearlySeptember

Priscilla VR VR VR R70-90%darkredblushoveryellowgreen,harvestmid-September

Sundance VR VR VR VR

Yellow,occasionallyrussetsinstemcavity,harvestmid-October,goodforsouthernOhioclimate

William’sPride VR VR R R darkred,harvestlateJulyor

earlyAugust

Winesap VS R S R Deepred,harvestmid-October

Table1.AppleVarietiesforHomePlantingsResistancetodiseasesotherthanapplescabhasnotbeenfullyevaluatedandmayormaynotdifferinsomelocationsfromthatreportedhere.Allapplesrequirecross-pollinationbyadifferentvariety.Winesapcannotserveasapollinizerbecauseithassterilepollen.

AS=applescab,CR=cedarapplerust,FB=fireblight,PM=powderymildew.VR=veryresistant,R=resistant,MR=moderatelyresistant,S=susceptible,— =insufficientinformation

culturalmethods.Alistofbiopesticides availableforhomeownersisprovidedinTable3.

Disease Management Home Apple Plantings -page 3

CommonDiseasesofHomeApplePlantingsinOhioApplescab. ApplescabisthemostimportantfungaldiseaseinOhioandismostsevereinwetsprings.Thefunguscausescircular,olivebrowntoblackcoloredspotsontheleaves,fruitandyoungstemsofthetree.Fruitlesionsaregenerallysuperficialanddonotalterthetasteofthefruit.Heavilydiseasedtreeswillprematurelylosetheirleavesandapples.Thefungusoverwintersonfallenleaves.Diseaseisbestcontrolledbyplantingresistantvarieties.Rakinganddestroyingleavesandfruitthathavefallenwillhelptopreventscabthefollowingspring.Leaves,stemsandfruitcanbeprotectedwithsyntheticchemicalsappliedbeginningatgreentip(budsbegintoshowgreentissue)andcontinuingthroughoutthesummer.

Fireblight. Fireblightisabacterialdiseasethatcaneventuallykillatreeifthediseaseisnotcontrolled.Fortunately,thisdiseaseissporadicandonlyanoccasionalproblemforbackyardgrowers.Thediseaseaffectsallpartsofthetreeincludingtheflowers,leaves,shoots,fruitandtrunk.Infectedtissuesarecharacterizedbytheirblackened,burnedappearance,hencethenamefireblight.Infectedshootsoftenhaveacrook-shapeappearance.Duringwarmandwetweatherdiseasedtissuemayoozewithbacteria.Varietiesvaryconsiderablyintheirsusceptibilitytofireblightbutplantingvarieties(androotstocks)thatareresistanttofireblightisthemosteffectivewaytopreventthedisease.MM.111andM.7EMLArootstocksareresistanttofireblight.Iftreesshowsymptomsoffireblight,infectedbranchesortwigsshouldbecutbacktohealthywoodduringthedormantseason.Diseasecanalsobeminimizedbyavoidingheavyapplicationsofnitrogeninthespringasthispromotesvigorousshootgrowth.Fungicideswillnoteffectivelycontrolfireblight.Theantibioticstreptomycincanbeappliedduringbloomtopreventnewinfections.

Powderymildew.PowderymildewisafungaldiseasethatisgenerallynotaprobleminOhio.Thefungusprefershotandfairlydrysummers,whichisnottypicalofmostsummersinOhio.Signsofinfectionappearaswhitepowderygrowthontheshoots,leaves,blossombuds,andimmaturetwigsofapple.Incasesofsevereinfection,theskinofthefruitwillbelightbrownincolorandroughtothe

AppleScabMelanieLewisIvey,TheOhio

StateUniversity

SummerFruitRotMelanieLewisIvey,TheOhio

StateUniversity

FireBlightMarcusMcCartney,TheOhioStateUniversityExtension

PowderyMildewSashaMarine,Virginia

PolytechnicInstituteandStateUniversity

touch,whichiscalledrussetting.Duringthedormantseason,thetipsofdiseasedtwigswillhaveafrostywhiteappearance.Thediseaseiseffectivelycontrolledbyplantingresistantvarieties.Pruninganddestroyingdiseasedtwigsduringthedormantseasonwillhelptoreducenewinfectionsinthespring.Fungicidesandbiopesticides canalsobeusedbeginningbeforetheblossomsstartshowingapinkcolorandrepeatedthroughoutthesummer.

Summerfruitrots. Therearethreefungalfruitrots(Blackrot,WhiterotandBitterrot)thatcancauseapplefruittorotwhilestillonthetree.Theblackrotfunguscaninfectfruitduringwarmrainsanytimefrom petalfalltoharvestbutsymptomsdon’tshowuponthefruituntilitbeginstoripen.Large,tantoblackcoloredlesionsthatformonthecalyxendofthefruitarefirmanddryaretypicalofblackrot.Incontrast,whiterotlesionsaresoftwithanapplesauceconsistency.Fruitwithwhiterotoften

Disease Management Home Apple Plantings -page 4

Table2.FungicidesforUseinHomeApplePlantings

Fungicide TradeNamesDiseasesControlled

RecommendedRate(PerGallonofWater)

calciumchloride*

Calcium-25ferti-lomeYieldBoosterTetraCor-ClearDryCalcium

BitterpitCorkspot

1.5tablespoons

captan Hi-YieldCaptan 50WFungicide ApplescabFlyspeckFruitrotsSootyblotch

1-1.5tablespoons

copper Liqui-CopCopperFungicidalspray

Fireblight 4-6teaspoons(silverto½inchgreentiponly)

mancozeb Bonide Mancozeb Flowable withZinc

ApplescabJuniperrusts

5teaspoons

myclobutanil Spectracide Immunox Multi-purposeFungicide

ApplescabCedarapplerustPowderymildew

4teaspoons

sulfur Bonide SulfurPlantFungicideSulfurSaferBrandGardenFungicideII

FruitrotsCedarapplerustPowderymildewSootyblotch

1-2½ tablespoons

*Donotapplycalciumchloridesprayswhentemperatureisabove85degreesFandrinsesprayerwellafterusebecausecalciumchlorideiscorrosive.

Biopesticide DiseasesControlled

RecommendedRate(PerGallonofWater)

BayerAdvancedSerenadeGardenDiseaseControl

Fireblight 4-8tablespoons

GreenCure FoliarFungicide

ApplescabFlyspeckPowderymildew

1-2tablespoons

SafeGro MildewCure Powderymildew 3tablespoons

NeemOils(manybrands)

Powderymildew Refertoproductlabels

BioWorksMilStop Powderymildew 1tablespoons

BioSafe DiseaseControl Powderymildew 1.5tablespoons

Organocide PlantDoctor Applescab 3-4teaspoons

Table3.Biopesticides forUseinHomeApplePlantings

Disease Management Home Apple Plantings -page 5

haveasoursmellwhenyoucutthemopen.Whiterotinfectionsprimarilyoccurduringtheheatofthesummer.Bitterrotisfavoredbyhotandhumidweatherduringmidtolatesummer.Symptomsofbitterrotincludecircularlesionsthatareslightlysunken.Indampweather,massesoforangesporesforminthecenterofbitterrotlesions.Fungicideappliedbeginningatpetalfallandcontinuingthroughharvestwillprovidegoodcontroloffruitrots.Therearenoeffectivebiopesticides forfruitrotcontrol.Topreventfruitrotsfrombeingayearlyproblemdiseasedfruitonthetreesandgroundshouldberemovedanddestroyed.

Flyspeckandsootyblotch. Flyspeckandsootyblotcharetwodifferentdiseases,causedbydifferentfungibuttheycommonlyoccurtogetheronthesamefruit.Bothdiseasesaremostcommonduringyearswithcoolwetsprings,rainsinlatesummer,andlowtemperaturesinearlyfall.Althoughallapplevarietiesaresusceptibletoinfectionbybothfungi,symptomsaremostsevereonyelloworlight-coloredvarieties.Sootyblotchappearsasdullblacktogreycoloredblotchesonthefruit.Flyspeckappearsassmallgroupsofblackshinyrounddotsthatmayormaynotformwithinsootyblotchpatches.Sootyblotchandflyspecksymptomsaresuperficialonthefruitandcanberemovedbywashingorrubbingthefruit.Annualpruningoftreestopromotegoodairflowthroughthecanopyandrapidfruitdryingisaveryeffectivemanagementstrategy.Fungicidesandbiopesticidescanbeusedtocontrolbothdiseases,howeverbecausethediseasesdon’taffectfruitqualityandthesymptomscanberubbedoff,fungicidesandbiopesticides arenotrecommendedforhomeplantings.

Cedarapplerust. Cedarapplerustiscausedbyarustfungusandisaproblemwhenappleandcertainspeciesofjuniperandredcedargrowincloseproximity.Thecedarapplerustfunguscausesbrightyellow-orangeorreddishspotsonappleleaves.Occasionallylesionswillalsoappearonthecalyxendoffruit.Resistantvarietiesshouldbeplantedinyardsthathavejunipersorredcedarsnearby(uptoamile).Forhomeownerswhowantjuniperandredcedartreesintheiryard,theyshouldconsiderplantingrustresistantvarieties(seeOSUExtensionFactsheetHYG-3055-08foralistofjuniperandcedarvarietieswithresistancetocedarapplerust).Fungicidesappliedbeginningattightcluster(blossombudsthatare

FlyspeckandSootyBlotch

JannaBeckerman,PurdueUniversity

mostlyexposedandtightlygrouped)canprotectappletreesfromrustinfections.Therearenoeffectivebiopesticides forcedarapplerust.

CedarAppleRustonCrabapple

RachelMedina,TheOhioStateUniversity

CedarAppleRustonRedCedar

DavidTaylor,USDAForestService

CommonInjuriesofHomeApplePlantingsinOhioNecroticleafblotch. NecroticleafblotchisacommonbutminorproblemthatappearstoberestrictedtotheGoldenDeliciouscultivarofapples.Thecauseoftheproblemisnotknown.NecroticleafblotchusuallyappearsinlateJuneorearlyJulyandmatureleavesonrapid-growingshootsareusuallytheonlypartofthetreethatshowssymptoms.Symptomsbeginasblotchingontheleaves,followedbyyellowinganddefoliation.Treesthathaveabiennialbearinghabitoralightfruitcroparemorepronetonecroticleafblotchthananannualmoderatecropoffruit.Treesprunedtohaveacentralleadertendtohavelessnecroticleafscorchthanthosethatareprunedtoanopencenter.Fungicidesandbiopesticides arenotrecommended.

Disease Management Home Apple Plantings -page 6

Bitterpitandcorkspot. Bitterpitandcorkspotarephysiologicaldisordersthataffectfruitquality.Theyarecausedbylowlevelsofcalciuminthefruit.LowsoilpH,excessivenitrogen,rapidshootgrowth,andlargefruitfromtreeswithlightcropsareassociatedwithincreasedincidenceofthesedisorders.Corkspotappearsanywhereonthefruitasgreendimplesordepressions.Whenthefruitispealedacorkybrownspotisunderthedimpleordepression.Bitterpitappearsassightdepressionsgenerallyonthecalyxendofthefruit.However,insomeinstancesthesymptomsmaynotbeapparentonthefruitsurfacebutappearundertheskin.Undertheskintherewillbedry,brownspongyspots.Appleswithbitterpitoftenhaveabittertaste.Symptomsofbothdiseasescanbedifficulttodistinguishfromdamagecausedbyinsects.Forlongtermcontrolofbitterrotandcorkspot,soillimingatplantingandthreetofiveyearintervalsafterplantingissuggested.Asoiltestshouldbeconductedtodeterminetheamountoflimestonetoaddtothesoil.Foliarapplicationofcalciumchloridebeginningtwoweeksafterfullbloomandcontinuingat10to14dayintervalsthereaftermayhelpreducecorksspotandbitterpitinestablishedtrees.

NecroticLeafBlotchMarkLongstroth,MichiganStateUniversity

The College of Food, Agricultural, and Environmental Sciences and its academic and research departments including, Ohio Agricultural Research and Development Center (OARDC), Agricultural Technical Institute (ATI) and Ohio State University Extension embraces human diversity and is committed to ensuring that all research and related educational programs are available to clientele on a nondiscriminatory basis without regard to age, ancestry, color, disability, gender identity or expression, genetic information, HIV/AIDS status, military status, national origin, race, religion, sex, sexual orientation, or veteran status. This statement is in accordance with United States Civil Rights Laws and the USDA.

Cathann A. Kress, Ph.D., Vice President for Agricultural Administration & Dean

For Deaf and Hard of Hearing, please contact the College of Food, Agricultural, and Environmental Sciences using your preferred communication (e-mail, relay services, or video relay services). Phone 1-800-750-0750 between 8 a.m. and 5 p.m. EST Monday through Friday. Inform the operator to dial 614-292-6891.

Copyright © 2017, The Ohio State University

MelanieL.LewisIvey,AssistantProfessorDepartmentofPlantPathology,Wooster,OH44691

PPSeriesNo.15301/18

BitterPitPoliana Francescatto,Cornell

University

CorkSpotMikeEllis,TheOhioState

University