DEPARTMENT OF PLANT PATHOLOGY Introduction ......Fire blight.Fire blight is a bacterial disease that...
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Introduction Disease Management Prevention is the key to disease management in the home garden. There are several disease management options for the home apple grower that have minimal impact on the growing environment yet help to maintain a healthy crop. Creating an optimal growing environment for apples will minimize plant stress, which in turn will reduce plant disease susceptibility and ultimately improve crop yield and the aesthetics of the planting. Several synthetic chemicals and natural products (also called biopesticides) are available to aid in the management of plant diseases, but they should always be used in conjunction with cultural practices intended to modify the environment to make it less conducive to disease development. Site Selection and Preparation. The most important management decision is selecting where to plant your apple trees. Pre-existing pathogens (fungi, bacteria, virus, and nematodes) can infect new trees, causing replant disease (gradual tree decline and lack of vigor). Before planting new trees into a site previously planted with apples, remove as many of the old roots as possible. Some crabapple, juniper, and cedar varieties are a source of important fungi that cause disease in apples. When selecting a location for your apple trees consider planting the trees up wind of any crabapple, juniper or cedar trees that you may have in your yard. Choose a sunny (6 to 8 hours of sunlight per day), well-drained location with a slight southern facing slope. Soil is the foundation for healthy and productive trees. Soil temperature, moisture, pH and fertility all influence a soil pathogen’s ability to survive and colonize plants. Apples will grow in a wide range of soil types but grow best in sandy loam, loam, or silt loam soils. Ideal soil pH for apples is 6.0-7.0. Have your soil tested annually to determine the pH, salts, nutrients and organic matter levels, and water holding capacity. There is probably nothing more frustrating for a home gardener than to see the fruits of his or her labors lost to diseases and other pests. Diseases occur when environmental conditions are suitable for pathogens to attack the host plant. Some pathogens attack a wide variety of plants, whereas others attack only specific plants. Additionally, some pathogens can attack all plant parts, whereas others attack only selected tissues (i.e. flowers, fruit, roots etc.). Many types of organisms cause infectious diseases of plants, but the five major groups of plant pathogens are the fungi, water molds, bacteria, viruses and nematodes. Adverse environmental conditions also can cause disease-like symptoms on plants; referred to as disorders. These include improper soil pH, nutrient deficiencies and toxicities, soil compaction, excess water, herbicide damage and more. Plants weakened by adverse environmental conditions may be further predisposed to attack by pathogens. Successful disease management begins with accurate identification of the cause of the problem. Knowing the common diseases of individual crops aids greatly in disease identification and management. Many diseases are readily identified based on characteristic signs (observation of the pathogen itself) and symptoms (observation of damage to the plant) of disease. The identification of other diseases requires microscopic examination of diseased tissues or even more sophisticated laboratory techniques, which are available through the C. Wayne Ellett Plant & Pest Diagnostic Clinic, Columbus OH. PP Series No. 153 DEPARTMENT OF PLANT PATHOLOGY
Transcript of DEPARTMENT OF PLANT PATHOLOGY Introduction ......Fire blight.Fire blight is a bacterial disease that...
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.
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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
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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
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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.
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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.
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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
