Stem-End Rot

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Material Information

Title:
Stem-End Rot
Physical Description:
Fact sheet
Creator:
Kucharek, T.A.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

Notes

Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"Publication date: June 1992."
General Note:
"PP-149"

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Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004617:00001


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FactSheetPP-149 June1992Stem-EndRot1 T.A.KucharekandG.E.Brown2Thefungus Diaporthecitri Wolfcausesstem-end rot.Stem-endrotoccursasapostharvestdecayinthe freshmarkettradewherelong-termhandling,storing, andtransportingareinvolved.Stem-endrotoffruit occurs10-20daysafterharvestduringstorageor transitmostcommonlyinthelatterpartofthe harvestseason(January-June).Becausefruit intendedforprocessingisusuallynotheldformore thanoneweek,stem-endrotisoflittleconsequence onfruitprocessing.Stem-endrotisofconsequence onlyforfreshmarketcitrus.FACTORSNECESSARYFORINFECTIONForinfectionbythefungustooccur,theremust berecentlykilledyoungtwigsinthetreecanopyto supportsporeproduction.Temperatureandrainfall conditionsregulatediseaseseverity.Afteraspore landsonsusceptibletissue,aperiodof10-12hoursof moistureisrequiredforinfectionat77F(25C) whileat59F(15C)18-24hoursofwetnessare necessaryforinfection.Thusextendedwetperiods resultingfromafternoonrainshowersplusdew periodsinMayandJunecoupledwithwarmer temperaturesduringthesemonthscreatefavorable weatherforinfection.Incontrast,rainfallpriorto MayincentralandsouthFloridaisassociatedwith fast-movingcoldfrontsthatarequicklyfollowedby temperaturesthatarelessfavorable(toocool)for infection.Also,windsbehindthefrontquicklydry surfacemoistureonplanttissue.SEASONALDEVELOPMENTThefungus Diaporthecitri producessporescalled ascospores(sexuallyproduced)andpycnidiospores (asexuallyproduced).Thislattersporetypeisthepart ofthelifecyclethatprovidesmostoftheinoculum fordiseaseandoftenisreferredtoas Phomopsiscitri Ascosporesareformedwithinavesicle-likestructure ondecayingwoodonthesoilorondeadbranches remainingonthetreeorinbrushsites.Thesespores areproducedinrelativelysmallnumbersand contributeslightlytodiseasepotentialinagrove. Theirmaincontributiontodiseasedevelopment relatestospreadofthefungusoverlongdistances becauseascosporesarewindborne. Pycnidiospores,ontheotherhand,areproduced abundantlyondeadbrancheswithinaflask-shaped structure(pycnidium).Theyprovideforshortdistance spreadwithinatreeorfromonetreetoanadjacent treebyrainsplash.Evenmorerestrictedmovement ofthesesporescanoccurbyrainorirrigationwater washingoverinfectedbranchesanddrippingonto lowerleaves,fruit,orlivebranchtissueofthetree canopy.Therefore,freeze-damagedcitrustrees,older groves,andpoorlymaintainedgroveswithmuchdead 1.ThisdocumentisFactSheetPP-149,aseriesofthePlantPathologyDepartment,FloridaCooperativeExtensionService,InstituteofFood andAgriculturalSciences,UniversityofFlorida.Publicationdate:June1992. 2.T.A.Kucharek,Professor,ExtensionPlantPathologist,DepartmentofPlantPathology,Gainesville,G.E.Brown,AdjunctProfessor, Pathologist,CitrusResearchandEducationCenter,LakeAlfred,InstituteofFoodandAgriculturalSciences,UniversityofFlorida, Florida. Tradenames,whereused,aregivenforthepurposeofprovidingspecificinformation.Theydonotconstituteanendorsementorguaranteeof productsnamed,nordoesitimplycriticismofproductsnotnamed. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

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Stem-EndRot Page2woodshouldbeconsideredhighstemendrot incidenceareas.Alltypesofcitrusaresusceptible. Otherhostsforthisfungushavenotbeenidentified. TemperatureandmoistureconditionsafterMay duringthesummermonthsarefavorableforspore productionandinfection.Pycnidiosporesofthe funguscarriedinwatertoimmaturefruitgerminate onnecrotictissueofthecalyxsurface,andthefungus remainsquiescentuntilaftermaturefruitare harvested.Stemendrotdevelopswhenhyphae (growthfilaments)ofthefungusgrowfromnecrotic tissuethroughtheabscissionareaintothebaseofthe fruit. Warmtemperaturesassociatedwithethylene degreeningafterharvestaremorefavorablefor developmentof Diplodianatalensis,theother stem-endrotfungus,thanforgrowthofPhomopsis. PhomopsisbecomesmoreprevalentthanDiplodia laterintheseasonfromJanuarytoJunewhen naturallycoloredfruitdonotrequiredegreening.STEM-ENDROTSYMPTOMSSymptomsofstem-endrotusuallybegintoappear 10daysafterharvest.Theinfectedareaissoft,tanor brown.Theinternalcoreofthefruitbecomesinfected andturnsdark.Laterseasonfruitaremoreaptto havestem-endrotthanearlyseasonfruit.CONTROLRECOMMENDATIONSStem-endrotisreducedbyusingcontrol measuresinthefieldduringproductionand additionalmeasuresduringpostharvesthandling periods.Becausethecalyxofimmaturefruitonthe treeisalsoinfectedduringperiodsofmelanose infection,fungicidespraysandremovalofdeadwood (sourceofspores)formelanosecontrolwill contributetoPhomopsisstem-endrotcontrol.Such beneficialeffectsmaynotshowupuntilthefruitis harvested(possiblymonthslater)andstoredatcooler temperatures. Seethe FloridaCitrusPestManagementGuide : PostharvestDecay-Stem-EndRotandGreenMold forcurrentcommercialfungiciderecommendations. Inthepackinghouse,theuseoffungicidesina postharvestapplicationarenecessaryregardlessof priorcontrolmeasures.Applicationoffungicideswith waterissuperiortotheincorporationoffungicidesin thewax.Throughoutharvestandpostharvestperiods, fruitshouldnotbehandledinaroughfashion.