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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

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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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