Scab Management: It Takes an Integrated Approach
USWBSI 05/12/15 ScabManagement:ItTakesanIntegratedApproach ByDonLilleboe* WhenitcomestomanagingFusariumHeadBlight(commonly referredtoas“scab”)inwheatandbarley,universitysmallgrainsspecialists emphasizethatthebestapproachisanintegratedonefocusingprimarilyonthe plantingofmoderatelyresistantvarietiesandtheuseofeffectivefungicides. “Noindividualapproachis100%effectiveatreducingscab—and particularlyreducingvomitoxin,”saysPiercePaul,Wooster‐basedplantpathologist withtheOhioStateExtension.“Fungicidesprovideabout50‐60%control,while resistanceprovidesabout50%controlrelativetothesusceptiblechecks.Togetthe bestcontrol,youhavetointegratemultiplestrategies,withfungicideandresistance beingthetwomainones.”Seedingintofieldspreviouslyplantedtonon‐cerealcrops reducestheriskofincreasedinoculumpressure;also,Paulandhisgrouphavebeen researchingthevalueofharvestingstrategiesthathelpimprovethequalityofthe grainharvestedfromscabbyfields.Theyfoundthatincreasingthecombinefan speedhelpstoblowoutscabby,light‐weightkernels,thusreducingthelevelof vomitoxinandFusarium‐damagedkernels(FDK)andincreasingthetestweightof grainharvestedfromscab‐affectedfields. “AnysinglemanagementpracticeusedalonetoreduceFHBandDON(the mycotoxinoftenresultingfromscabinfection)isnotenoughwhenweather conditionsarefavorableforFHB,”statesUniversityofIllinoisextensionplant pathologistCarlBradley.Speakingtowheatspecifically,whilenovarietyis completelyresistanttoscab,“thecombinationofa[moderately]resistantvariety andtheapplicationofaneffectivefungicide(eitherProsaro®orCaramba®)atthe correcttiming(beginningofflowering—Feekesgrowthstage10.5.1)willprovidea muchbetterlevelofcontrolthandoingeitherpracticealone,”Bradleyadvises. ShouldonebeunabletoapplyProsaroorCarambaonthedaythatmostofthefield isflowering,anapplicationtwotosixdaysafterthatwillstillhelpreducescaband vomitoxin,saysOhioState’sPaul. 1 USWBSI 05/12/15 Forbarley,fungicideapplicationshouldoccuratheading,saysAndrew Friskop,NorthDakotaStateUniversitysmallgrainsextensionplantpathologist. Whendecidingwhethertomakeanapplication,wheatandbarleygrowersoften relyuponexperienceand“gutinstinct,”Friskopnotes.But,helikewiseencourages producerstoutilizestateandnationalFHBpredictionmodels.TheFHBRisk AssessmentTool,fundedbytheU.S.Wheat&BarleyScabInitiative(USWBSI),is designedtogivegrowersandgrainindustrypersonnelvaluableadvancenoticeof potentialoutbreaksandtheriskofscab.Thistool,whichcanbeaccessedat http://www.wheatscab.psu.edu/riskTool.html,displaysdailyestimatesofdisease riskformorethan30states.Theriskmapsareaccompaniedbytimelycommentary fromdiseasespecialistsfromtheparticipatingstates. TheUSWBSIalsosponsorstheFusariumHeadBlight(FHB)ScabAlert,areal‐ timealertsystembasedoncommentaryfromsmallgrainsdiseasespecialists aroundthecountry.Alertsaredeliveredtosubscribersviaeithercellphonetext messagesoremail,warningthemwhenconditionsintheirareaarefavorablefor scabdevelopment.Thoseinterestedinsigningupforthesealertscandosoat http://scabusa.org/fhb_alert.php. DespiteuniversityextensionemphasisonanintegratedapproachtoFHB management,notallgrowersfollowthatadvice.“Unfortunately,itwasapparent thatnotenoughgrowersinIllinoisimplementedanintegratedmanagement approachinthe2014season,”Bradleysays,referringtolastyear’s“majorissues thatoccurredwithFHB,andespeciallyhighDONlevels,despitemanyfields receivingafungicideapplication.”Numerousgrowersassumethatagoodfungicide cancurealldiseaseproblems,hecontinues.“Butfungicidealonedoesnotgofar enoughforcontrolofFHBandDON.” NDSU’sFriskopbelievestheuseofanintegratedstrategyvariesfromregion toregionwithinhisstate.“Growerswhodealwithchronicscabproblemslikelywill employanintegratedapproach;andtherefore,Iwouldconsiderittobehighly adoptedintheseregions,”herelates.“Howeverotherregionsthathaveinfrequent scabepidemicsmaychooseoneoftwoFHBmanagementtoolsinsteadofaholistic integratedapproach.”Also,hepointsout,FHB‐resistantvarietiesofdurumwheat 2 USWBSI 05/12/15 andbarleyarenotyetaswidelyavailableinNorthDakota,comparedtohardred springwheat. Aswheatandbarleybreedersdevelopandreleasemorevarietieswithat leastmoderateresistancetoFusariumHeadBlight,itishoped—andexpected— thatthepercentageofsmallgrainacreageplantedtosuchvarietieswilltrend upward.Onechallengefacingextensioneducators,however,ishowtomaintain producers’FHB“radaralert”onaregularbasis,notjustinthoseyearswhenscab rearsitsheadintheirlocaletoaneconomicallysignificantdegree.“It’sagoodthing wedon’tgetscabeveryyear;butthefactthatwedon’t[likewisemeans]it’shardto keeppeoplefocusedonscab,”affirmsPiercePaul.“Thesameappliestousingthe forecastingsystem,usingthetoolsthatareavailableforscabmanagement.When scabis‘offtheradarscreen,’nobodywantstohearaboutit.Butwehavetokeepat it.” *DonLilleboeisanagriculturalwriter/editorbasedatFargo,ND. 3
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