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ManagingFusariumDiseasesofVegetables
LenTesoriero
Overview
● WhatdoweknowaboutthefungusFusarium?
● WhatdiseasesdoFusariumspeciescauseonvegetables?
● WhatconditionsfavourFusariumdiseasesandhowdoesthefungusspread?
● Whatintegratedmanagementoptionsarethere?
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Thefungus,Fusarium
● Fusarium isacommonsoilborne fungus– mostspeciesarecommonsaprophyteswhileafewareimportantplantpathogens
● PlantpathogenicFusarium fungiarenecrotrophs (theyfeedondeadplanttissue)– whichimpliestheyproduceenzymesortoxinsthatkillplantcellsastheyinvade
● Hostspecialisedstrains(f.spp.)andracesoccur
● Fusarium pathogensofvegetablesproducecharacteristicbanana-shapedspores(macroconidia),aswellasothersmaller(jellybean)ones(microconidia)andsmallrestingbodies(chlamydospores &sclerotia)
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Fusariumspores&cultures
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KeyFusariumdiseasesofVegetables
● WiltandYellowsdiseases– manydifferenthost-specificstrainsofFusariumoxysporum
● NotallFusariumwiltpathogensareknowntooccurinAustralia– importantBiosecurityimplications
● Stem,crown,androotrots– mostlycertainF.oxysporumandF.solani strains;occasionallyotherFusarium speciesinvolved(e.g.F.avenaceum associatedwithdryrotofcarrots;&variousotherspeciesonasparaguscrowns)
● F.solani causesafruit&stemrotoncapsicums&pumpkins
● Dampingoff,wiltandrootrotdiseasecomplexeswithotherfungi&/oroomycetes– e.g.beans,peas,cucumbers
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ExamplesofFusariumwiltdiseases
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Host Fusarium oxysporumstrain (f.sp.)
Present in Australia
Beans phaseoli -?Brassicas conglutinans +Capsicums capsici -Cucurbits cucumerinum
melonis; niveumluffae; lagenariaemomordicae; benincasae
++--
Eggplant melongenae -Lettuce lactucae -Onions etc cepae -?Peas pisi +Snake beans tracheiphilum +Spinach spinaciae +
Fusariumwiltofcucumbers
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Fusariumwiltofspinach
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Basalplaterotofleeks
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F.solani onpumpkin
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Fusariumwiltoftomatoes
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Source,spreadandfavouredconditions
● Canbeacontaminantofseedandspreadsinnurseries
● Thefungussurvivesformanyyearsinsoilonfarmsandisdifficulttoeradicate
● Spreadwithsoilandmedia,water,sciarid flies,contaminatedequipment&workers(hands,footwear&clothing)
● Favouredbyammoniumnitrogen;KdeficiencyfavoursBrassicayellows
● Certainwiltdiseasesarefavouredinparticulartemperatureranges
● Plantstress– water,nutrition,fruitload– favoursdiseaseCopyright©AHR
AdditionofureastimulatesFusarium wilt
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AdditionofureastimulatesFusarium wilt
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SomemechanismsforN-formxDisease
● NH4decreasessoilpH&increasesaminoacidinrootexudates– influencesrhizospherebiota
● NH4 stimulatesgerminationofpathogenpropagules(Fusarium solani &F.oxysporum)
● NH4 increasesvirulenceofF.oxysporum
● NH4 repressesuptakeofNO3 andKandstimulatesCluptake– diseaseseverityisgreaterwhentheK:Clratio≠3.5
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Keymanagementstrategies● Resistantvarieties– raceresistancegenes
● Graftingontoresistantrootstocks
● Avoidammonium(NH4+)fertilisers
● Avoidover-watering– uselessmoreoften
● Preventativemeasures- crop&farmhygiene&biosecurity:e.g.comeclean– goclean
● Controlsciarid flies&soil-borneinsectpests
● Removeorburyplantwaste
● Croprotation,covercrops,organicamendments,microbialbiocontrols;plantdefenceactivators;noregisteredchemicals exceptfumigation
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Preventcross-contamination
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• Seedling hygiene
Crophygiene
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• Minimise plant contact• Remove crop waste directly
Conclusions
● MostvegetablesaresusceptibletoaFusariumdisease
● TherearesomestrainsofthispathogenthatarenotknowntooccurinAustralia
● Fusariumisdifficulttomanagebecauseitbecomesendemiconfarms&chemicalcontrolsarenoteffective
● Anintegratedandholisticapproachistheonlyeffectivewaytomanagethem
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ThankYou
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