Hands-on identification of vegetable diseases: Tomato
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Hands-on identification of vegetable diseases: Tomato Theme: How to diagnose a specific disease from diseases or disorders with similar symptoms. North Florida Research and Education Center, Quincy, FL Department of Plant Pathology, University of Florida, Gainesville, FL University of Florida Cooperative Extension Mathews Paret, Gary Vallad, Shouan Zhang, Nicholas Dufault, Rosemary Loria, Fanny Iriarte, Susannah Da Silva, Steve Olson, Josh Freeman
Transcript of Hands-on identification of vegetable diseases: Tomato
Hands-onidentificationofvegetablediseases:Tomato
Theme:Howtodiagnoseaspecificdiseasefromdiseasesordisorderswithsimilarsymptoms.
NorthFloridaResearchandEducationCenter,Quincy,FLDepartmentofPlantPathology,UniversityofFlorida,Gainesville,FLUniversityofFloridaCooperativeExtension
MathewsParet,Gary Vallad, Shouan Zhang, Nicholas Dufault, Rosemary Loria, Fanny Iriarte, Susannah Da Silva, Steve Olson, Josh Freeman
Tomato
2014,FL(USDA-NASS,2015)33,000acresharvestedinFL,#1intheU.S(97,600acresharvestedintheU.S).>$437millionFarmValue,#1istheU.S.($1.1billionFarmvalueintheU.S)
Tomatosectiondiscussionlayout
• Scenario1:Wilts• Scenario2:Spots• Scenario3:Yellowing,stunting• Scenario4:Fruitdamage• Scenario5:Canker
Scenario1a:Thatwasafinemorning;JenniferBeardenisvisitingatomatofarminOkaloosacountyandnoticestheplantwilting.Thegrowerneedstoknowwhatisthecauseofwiltingandasolution!
Possiblereasons:1. Bacterialwilt:Bacterial(B)2. Tomatospottedwilt:Viral(V)3. Fusariumwilt:Fungal(F)4. Verticilliumwilt:F5. Southernblight:F6. Sclerotiniablight:F7. Bacterialpithnecrosis:B8. Root-knot:Nematodes9. Lightningstrike:Abiotic(A)10. Lackofwater:Physiological(P)11. Excessivesoilmoisture:P
Thereisonlyonefungaldiseasethatisknowntocauseawhitefungalmycelialmatlikegrowthonthecollarregionoftheplantandtheadjacentsoil:SouthernblightcausedbySclerotiumrolfsii
DefinitiveconfirmationofSouthernblightisthemustardlikestructureknownassclerotiawhichiswhite,lightbrown,ordarkbrownincolor.Atlaterstages,youmayonlyseesclerotiaandnotthemycelium.
Ifitisnotsouthernblight,itmaybeSclerotiniablightcausedbySclerotiniasclerotiorum
YoumayseewhitefungalgrowthontheblightedstemincaseofSclerotiniablight
DefinitiveconfirmationofSclerotiniablight:blackfungalstructures(sclerotia)canbeseeninsidetheblightedstemwiththewhitefungalgrowth.
Ifitisnotsclerotiniablight,itmaybeBacterialwiltcausedbyRalstoniasolanacearum
BacterialstreamingfromcutsectionofthestemisadefinitiveconfirmationofBacterialwilt
Ifisnotbacterialwilt,maybeitisFusariumwiltcausedbyF.oxysporumf.sp.lycopersici,orVerticilliumwiltcausedbyV.dahliae,andV.albo-atrum.Allthesediseasescancausevasculardiscoloration.
Wilting,andyellowingoftheleavesmaybemostlikelyduetoFusariumwilt.Culturinginthelabrequiredforconfirmation.
TomatoSpottedWiltiscausedbyaTospovirusTSWVandisvectoredbyvariousthripsspecies
Acombinationofsymptomscanprovideadefinitiveconfirmation.Wilting,CurlingandPurplingofleaves
Black/Purplishpatternsontheleaves
Smallpurplishspotscoalesceonleaves
CombinationofsymptomscanprovideadefinitiveconfirmationforTSWV:Circularpatternsonthefruit
VarioustypesoffruitsymptomsassociatedwithTomatoSpottedWilt
Scenario1b:AsmallproducerinJacksoncountyencounterssomethingunusual.Asectionofthefieldiscompletelywilted.HecallsMattLollartocheckhisplot.Thegrowermentionedthathegotagood2inchesofrainyesterdayafteralongdryperiod.Buthedidn’trevealalltheinformation.Mattcheckinghisplantsfoundsomethingdifferentthannormalwiltdiseases.Henoticesvascularsystemcollapsebuthadauniqueladderlikeappearance.
Basedonthesymptoms,Mattthoughtitcouldbe1. Bacterialpithnecrosis:B2. Lightningstrike:A
Theuniquepatternofwilting(proceedingalongabed),andtheladder-likeappearancewasduetolightningdamage.Thegrowerconfirmedthattherewaslightningthepreviousday.
Mattshouldhaveseenacompletecollapseofthevascularsystem,necroticpith,possiblyfruitnecrosisandplantyellowingifitwasBacterialpithnecrosiscausedbyPseudomonascorrugata.
WiltingofplantscausedbyBacterialpithnecrosis
Pseudomonascorrugataisaopportunisticbacteriathatwiltssectionsofthetheplantsasitinvadeswoundsonthestem;inthiscasethewoundisfromtyinginjury!
Ifnoneoftheissuesdiscussedbeforewerefound,checktheroots.Ifyoufindroot-galling,root-knotnematodesmaybethecauseofwiltingandstuntingoftheplants
Disease Managementoptions
1 Bacterialwilt a. Graftedplantswithhybridrootstocks,SARinducer2 Southernblight a. Fieldfumigation
3 Sclerotiniablight a. Fieldfumigation
4 Fusariumwilt(Races1,2and3areknown)
a. Resistantvarietiesb. Fieldfumigationc. Graftingwithresistantrootstocks
5 Verticilliumwilt(Races1and2known)
a. Resistantvarietiesb. Fieldfumigationc. Graftingwithresistantrootstocks
6 TomatoSpottedWilt(TSW)
a. Resistantvarietiesb. Reflectivemulchesc. Thripspesticidemanagementd. Kaoline. SARinducer
7 Bacterialpithnecrosis a. Avoidinjurytotheplants;tietheplantslateinthedaywhentheyaredryandavoidtyingduringexcessivemoisture
8 Root-knot a. Grafting,resistantvarieties,Fieldfumigation
Productioninfieldswithnohistoryofthediseaseisanimportantmanagementoptionforallsoil-borneorganisms.
Scenario2:MarkMaudlingetsacallfromatomatogrowerinJacksoncountywhohasbeennoticingnumerousspotsonleaves.Thegrowerwouldliketoknowthecauseandhowtomanageit.
Possiblereasons:1. Bacterialspot:B2. Bacterialspeck:B3. Syringaeleafspot:B4. Targetspot:F5. Earlyblight:F6. Spraydamage:P7. TSW
1. Bacterialspot:B2. Bacterialspeck:B3. Syringaeleafspot:B4. Targetspot:F5. Earlyblight:F6. Spraydamage:P7. TSW
Firststep:Markbringsbackasampletothecountyofficeandconductsabacterialoozetest
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Ifthebacterialoozetestispositive(+),thediseasemaybeearlystagesofbacterialspotcausedbyXanthomonasperforans
Duringlatestagesofbacterialspot;thecentralportionofthespotsfalldown,whichisagoodindicatorthatthediseasemaybebacterialspot.
Anothergoodindicatorofbacterialspotisthesmallraisedlesionsonthefruits.
Ifthediseasesymptomsdoesn’tlooklikebacterialspotitcouldbeinsteadBacterialspeckcausedbyPseudomonassyringaepv.tomato,SyringaeleafspotcausedbyPseudomonassyringaepv.syringae.However,fielddiagnosisofthesediseasescanbedifficultandsamplesmayhavetobesendtoadiagnosticlabforID.
IfMarkgetsanegativebacterialoozetest,itcouldbeafungaldiseasecausingthespotsoritcouldbeTSW.However,basedonthelackofothercharacteristicsymptoms,MarkthinksitisnotTSW.ItcouldbeTargetspotcausedbyCorynesporacassicola
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Symptomsonleaves(2,3)aregoodindicators;onfruits(4,5)arecharacteristicforTargetspot.Lesionsaresunkenandwillhavecracksinthecentercomparedtoraisedandnocracksforbacterialspot.
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SymptomsofEarlyblightcausedbyAlternariasolani/A.tomatophilacanbeverysimilartotargetspotleafsymptoms.
Stemlesions
Blackshoulder-Alternariaalternata
ThestemandfruitlesionsaregoodindicatorsofBlackshoulder.
Otherspots,moldsandmildew1. Septorialeafspot:Septorialycopersici2. Grayleafspot:Stemphylliumsolani3. Lateblight:Phytophthorainfestans4. Phomarot:Phomadestructiva5. Cercosporaleafmold:Pseudocercosporafuligena6. Graymold:Botrytiscinerea7. Leafmold:Fulviafulva8. Powderymildew(Levelillula,Oidium)
Spotsandmoldscanbedifficultforfielddiagnosis.Ifyouarenotsure,sendthesampletoadiagnosticclinicforadefinitiveID.
Disease Managementoptions
1 BacterialspotBacterialspeckSyringaeleafspot
a. SARinducerb. Bacteriophagec. Copperhydroxide+Maneb/Mancozeb
2 Targetspot a. Fungicideapplication3 Earlyblight/Black
shouldera. Fungicideapplication
4 SeptorialeafspotGrayleafspotLateblightPhomarotCercosporaleafmoldGraymoldLeafmoldPowderymildew
a. Fungicideapplication
Floridaweatherconditionsareidealforoccurrenceoffoliardiseases.Thisnecessitatesthejudicioususeofprotectiveandsystemicfungicidesandrotatingfungicidechemistriesforeffectivediseasemanagement
Scenario3:IntheFallof2014,KeithWynnnoticedyellowingandstuntingofplantsinHamiltoncounty.Talkingwithotheragentsheshortlistedthepossiblereasons.
1. TomatoYellowLeafCurl:V2. TobaccoMosaic:V3. CucumberMosaic:V4. Littleleaf:P
Yellowing,stunting,andpresenceofwhitefliesundertheleavesorinthefieldinhighnumbersisastrongindicatorthatthediseaseisTomatoYellowLeafCurl(TYLC)causedbyaGeminivirusandvectoredbywhiteflies
Spidermitefeedingcanalsocauseleafspotsandsevereyellowingofplants.Checkundertheleavesformites.
UniquechloroticpatternontheleavesbetweentheveinsmaybeduetoTMV;aTobamovirus,thatisspreadbymechanicaltransmission
SevereshoestringleafsymptomscanbeduetoTMVorCMV(transmittedbyaphids)
Phenoxytype(IAA)herbicidedamagecanalsolooksimilartoCMVsymptoms
Interveinalchlorosis,invardcurlingoftheleaf,distortedleaf,crackingofthefruitmaybeduetolittleleaf(causenotknown)
Challenge question: A grower has tomatoes planted in a high tunnel in raised troughs that contain a mix of organic compost. Several weeks into the season the plants begin to exhibit leaf strapping and curling and growth rate nearly stops. He has a neighbor with a sod farm. He also has 2 acres of tomatoes that were just set outside that are not showing symptoms. What is most likely reason based on the information provided above. A. TMV transmitted within the high tunnel by workers B. Herbicide drift from the neighboring farm C. Herbicide carryover in the compost
Disease Managementoptions
1 TomatoYellowLeafCurl a. Resistantvarietiesb. Whiteflymanagement
2 TobaccoMosaic a. Greenhousesanitationofpruningknivesandequipmentsandworkersanitation.
3 CucumberMosaic a. Aphidpesticidemanagement
Managementoptions
Scenario4a:Forgetdiseasescausedbyplantpathogens,whataboutphysiologicalissuescausingfruitdamage.DavidNistleratClaycountyextensionofficegetsthesequestionsallthetime.
Possiblereasons:1. Blossomendrot:P2. ZebraStripe:P3. Catface:P4. Graywall:P5. PoxandGoldFleck:P6. Littleleaf:P
Blossom End Rot
Catface
Graywall
Zebra stripe Pox and Fleck
Gold fleck (thrips feeding or genetic)
Scenario5:BlakeThaxtonnoticedcankersonstem,lesionsonthefruits,blightingofleaves,andvasculardiscolorationduringoneofhisregularvisitstoagreenhouseproductionatSantarosacounty.Whatcouldbetheproblem.
Vasculardiscolorationinsideastemwithcanker
Possiblereason:1. Bacterialcanker:B
Wiltingoftheleavesandsevereblight
Unilateralwiltingoftheleavesandsevereblight
Bird’seyelesionsonafruit:Fieldproduction
Nettingofthefruit:Greenhouseproduction
Combinationofcanker,vasculardiscoloration,blighting,unilateralwilting,bird’seyelesions/nettingoffruitsisastrongindicatorthatthediseasemaybebacterialcankercausedbyClavibactermichiganensissubsp.michiganensis.
Disease Managementoptions
1 Bacterialcanker
a. Seedsanitationb. Pruningknivesandworker
sanitation
Now,thekeyquestionishowsymptomsofnutrientdeficienciesaredifferentthancausedbyplantdiseases?
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• Fieldidentificationbasedonkeysymptomscausedbyvariouspathogenscanbeaneffectivetoolforrapidrecommendationsatthecountylevel.
• However,ifyouarenotsure,usediagnosticfacilitiesatUFfordefinitiveconfirmation.
ContactforadditionalinformationMathewsL.ParetAssociateProfessorofPlantPathologyUniversityofFlorida,[email protected],850-875-7154
