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.
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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
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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.
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