SciencebehindtheResistanceManagementStrategyfordiamondback

moth(Plutellaxylostella)inAustraliancanolacrops

DevelopedbythegrainsNationalInsecticideResistanceManagement(NIRM)workinggroupoftheGrainsPestAdvisoryCommittee(GPAC)

Authors:MrGregBaker(SARDI),DrPaulUmina(cesar),DrMelinaMiles(QldDAFF),DrNancySchellhorn(CSIRO),ProfAryHoffmann(UniversityofMelbourne),DrOwainEdwards(CSIRO),DrGarryMcDonald(UniversityofMelbourne),ProfStephenPowles(UWA)&MrGeoffCornwell(DuPontCropProtection).SpecialthankstoPeterWatt(Elders),PhilBowden(PulseAustralia),SamHolmes(HolmesFarmConsulting),AndrewPfitzner(LandmarkPfitznerandKleinig),NigelMyers(LandmarkCummins),AmyWright(AgsaveMerchandise),OrvilleHildebrand(FPAG),KentWooding(Agrivision),KateWilson(Agrivision),CraigDrum(TatyoonRural),PhilHawker(WesternAGSupplies),SvetlanaMicic(DAFWA),PeterNorris(AgronomyforProfit),RichardQuinlan(PlanfarmAgronomy),KymPerry(SARDI),CropLifeAustraliaandtheGrainsResearch&DevelopmentCorporation.

June2017

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Table1.Backgroundinformationondiamondbackmoth(DBM),Plutellaxylostella

Attribute WhatisknownaboutDBM? References KnowledgegapsEconomicimportancetograins

• DBMisamajorpestofcanolaandmustard*crops,particularlyatfloweringandpodding,andofbrassicavegetablecropsandforagebrassicas.

• Economiclossestothecanolagrainsindustryareconsiderable.

• Economicimpactvariesacrossregionsandyearso regionscommonlyaffectedbyDBMincludeEyre

PeninsulaSAandthenorthernwheatbeltofWAo outbreakfrequencygenerally1in3-5years

• P.australianarecentlydescribedcrypticspecies.Economicstatusunknown.

Furlongetal.2008;Murrayetal.2013;Landry&Hebert2013.

• Modelstoforecastintensityofseasonaloutbreakswithindistrictsandacrossregions.

• PeststatusandbiologyofP.australiana.

Modeofreproduction

• Sexualreproduction,nocturnal.• Malesrespondtosexpheromonesreleasedbyreceptive

(calling)females.• Sexpheromonecomponentscharacterizedandavailablein

commercialblends.

Talekar&Shelton1993;Tamakietal.1977.

• Thepotentialofmatingdisruptionasacost-effectiveDBMmanagementtacticinvegetables.(Advantagetograins:reducetheselectionrateforinsecticideresistanceinAustralianDBMpops.)

Lifecycle(incl.#generations)

• AustralianclimatesupportsDBMdevelopmentandreproductionyear-round(exception:someinlanddesertregions).

• DBMtypicallycompletes3-5generationspercanolagrowingseason,8-12+generationspainbrassicavegetablecrops.

• DBMcanolainfestationsgenerallypeakinearly-midspring.Bythistimealllife-stagesoverlap(makingadifficultinsecticidetarget).

ZaluckiandFurlong2011.Ridland&Endersby2006.

• AccuratepredictionsofconditionsleadingtoDBMoutbreaksincanola.

Crophosts • Canolaandmustardgraincrops,brassicavegetablecrops • DynamicsofDBMmovement

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andforagebrassicas.• SignificantcanolacompensationtoDBMfoliardamage,

highlightingimportanceofthresholds.

Baker1985.

betweencanolaandotherbrassicacropsources.(KymPerryPhD)

Non-crophosts • Brassicaceaeweeds,e.g.Lincolnweed,mustardweed,turnipweed,Ward’sweed,dogweedetc..

• RecordedonnativeLepidiumhyssopifolium,andlikelytooccuronothernativeBrassicaceae.

Common1990. • RoleofweedhostsaslocalrefugiaforDBMandDBMparasitoidpops.

Distribution • Cosmopolitan,greatestpeststatusintropic-subtropiczone.Bioclimaticmodellingillustratesthepopulation-limitingeffectsofhighrainfallandextremetemperatures,whichcanprecludeyear-roundpersistenceinsomeglobalregions.

• Locally,Australiawide;verycommonacrossallgraingrowingregionsinWA,SA,VIC,NSWandQLD.

Zaluckietal.2012;Furlongetal.2013.

• SeasonalchangesinDBMdistributionincludingsource/sinkareas

Dispersal/movement • DBMisaseasonalmigrant,seekingnewhostsourceswhenthecurrenthostpatchsenesces.

• DBMflightactivityinsouthernAustraliaincreasesinspring,beforedecreasingduringsummer.

• InearlywinteryoungcanolacropsarecolonizedbyDBMmoths.Thesource(s)ofthesecolonizersisoftenuncertain,butinmanyinstancesisthoughttobelocalwildhosts(eg.southernEyrePeninsula,SA,whereinsecticideresistanceprofilesofDBMongreen-bridgeweedsandvolunteercanolamatchthoseofthelocalcanolacrops).

• GeneticanalysisshowsnostrongdifferentiationbetweenpopulationsofDBMacrossAustralia,suggestingwidespreadgeneflowacrossregionsofAustraliaand/orthattheywerederivedfromacommonancestralsourcepopulation(approx.130yearsago).

Endersbyetal.2006;Furlongetal.2008;Sawetal.2006;Schellhornetal.2008;Schellhornetal.2008;Schellhornetal.2004

• Knowledgeofdispersalecologyandsourcesofcrop-colonizingDBMpopulationsisrequiredforreliablepestforecasting.

• ThoughgeneticstudieshavefoundevidenceforfrequentgeneflowamongDBMpopulationswithinindividualregions(aroundtheworld),dispersal/migrationroutesremaintobeidentified.Newermoleculartoolsmayprovidemoreresolutioninthenearfuture.

Feedingbehaviour&oviposition

• Chewingpest;larvalfeedingcancauseextensivedamagetocanolafoliage,inflorescencesandpods.

Baker1985;Cooketal.2000;

• Refinementofeconomicthresholdsforcanolacropsunder

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behaviour • Olderlarvaefeedontheundersideofleaves,causingraggedholesand‘windows’withtheupperleafsurfaceintact.

• Canolahassignificantcapacitytocompensatefordefoliationloss.Howeversevereinfestationscancausecompletedefoliationandsubstantialyieldlosses.

• Asfloweringcommences,DBMlarvaecanmovetoandcauselossoffloralbuds,flowersandyoungpods,andlatercausescarringoftheouterwallsofmaturingpods.Thedamagetothesereproductivepartscanreduceseednumber&size.

• Economicthresholdsareavailable(basedon2000-02WAstudies.

Broadetal.2008;Broadetal.2008

differentfieldscenarios.

Chemicalcontrols • Chemicalsremaincentraltocontrolincanolaandalsointheforageandvegetablebrassicaindustries.

• Thereareapproximately170insecticideproductsregisteredinAustraliaforDBMcontrol,buttheseareprimarilyfromtwooldchemicalgroups-organophosphatesandsyntheticpyrethroids–towhichDBMhasevolvedhighlevelsofresistance.

• Since2012twonewerMOAinsecticideshavebeenregisteredforDBMcontrolincanolacrops(Group5spinetoramandGroup6emamectinbenzoate).(Spinetoramisalsoregisteredinforagebrassicas.)

• Inadditiontothesetwo,anotherfournewerinsecticideswithdifferentMOAareregisteredforDBMcontrolinbrassicavegetablecrops.

• Globally,resistancetoover82insecticidecompoundsrecorded.

Furlongetal.2008.Furlongetal.2013.

• Needformorealternativechemistries.

• Economicthresholdsand/orpredictivemodels.

• Measurementofthecost-effectivenessofBtspraycontrol(directcontrol+beneficialpreservationeffect).

Biologicalcontroloptions

• Threeparasitoids(Diadegmasemiclausum,DiadromuscollarisandCotesiaplutellae)havebeensuccessfully

Baker1985;Furlongetal.2008;Bianchi

• MonitoringtoolssothatbeneficiallevelscanbefactoredintoETspray

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introducedtoAustraliaforthebiologicalcontrolofDBM.• Theysupplementarangeofnativeparasitoids(e.g.

Apantelesippeus,Diadegmarapi)andvariouspolyphagouspredators(e.g.nabidandpentatomidbugs,coccinellids,hemerobiidlacewings,lycosidandotherspiders,etc.)thatprovidebioticregulationofDBM.

• EpizooticsofthefungalpathogenZoophthoraradicanscancausespectacularreductionsinDBMpopsincanolacrops.

etal.2009;Lietal.2007;Hamiltonetal.2004;Hamiltonetal.2006.

decisions.• Hostsourcesofbeneficials,

particularlyparasitoidpops,whichcolonizecanolacrops.

Othercontroloptions

• Matingdisruptionusingfemalesexpheromone.Potentiallyfeasibleforvegetablecropsusingnewapplicationtechnologies(eg.SPLAT®).NotpresentlybeingpracticedortrialledinAustralia.

• Magnet®Attract-and-Killtechnology(containsplantvolatilemothattractantsandthetoxicantspinetoram).BeingtestedasaDBMcontroltactic.

Wuetal.2012.PeterGregg(UNE),pers.comm.

*Mustard(Brassicajuncea)isalesscommonlygrownbrassicaoilseedcropinAustralia.Inthistableallfurtherreferencestocanola(B.napus)alsoapplytomustard.

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Table2.ProductswithlabelclaimsfordiamondbackmothcontrolinAustraliaIRACMoAgroup

Insecticidecategory Exampletradenames

Activeingredient Registeredcropsandpastures

Group1A Carbamates Carbaryl carbaryl BrassicavegetablesGroup1A Carbamates Lannate,Marlin methomyl Canola(WAonly)Group1B Organophosphates Lancer,Orthene acephate BrassicavegetablesGroup1B Organophosphates Chlorpyrifos,

Lorsban,StrikeOutchlorpyrifos Canola,brassicavegetables,foragebrassicas

Group1B Organophosphates Diazinon,Diazol diazinon Canola,brassicavegetablesGroup1B Organophosphates Hy-mal,Fyfanon maldison Canola,brassicavegetablesGroup1B Organophosphates Phosdrin mevinphos BrassicavegetablesGroup1B Organophosphates Tokuthion prothiofos BrassicavegetablesGroup1B Organophosphates Lepidex trichlorfon BrassicavegetablesGroup2B Phenylpyrazoles Regent,Fipronil Fipronil BrassicavegetablesGroup3A Pyrethroids Fastac,Dominex

Duo,Astoundalpha-cypermethrin Canola,brassicavegetables,foragebrassicas

Group3A Pyrethroids Chix,Banshee beta-cypermethrin Canola,brassicavegetablesGroup3A Pyrethroids ScudElite cypermethrin Canola,brassicavegetablesGroup3A Pyrethroids DecisOptions,

BallisticElitedeltamethrin Canola,brassicavegetables

Group3A Pyrethroids Trojan gamma-cyhalothrin Canola,brassicavegetablesGroup3A Pyrethroids KarateZeon,

Matadorlambda-cyhalothrin Canola,brassicavegetables,foragebrassicas

Group3A Pyrethroids Sumi-alphaFlex esfenvalerate Canola,brassicavegetablesGroup3A Pyrethroids Ambush,Hellfire,

Pounce,Axepermethrin Canola,brassicavegetables

Group3A Pyrethroids Klartan,Mavrik tau-fluvalinate BrassicavegetablesGroup5 Spinosyns SuccessNeo spinetoram Canola,brassicavegetables,foragebrassicasGroup6 Avermectins Affirm,Proclaim emamectinbenzoate Canola,brassicavegetables

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Group11A Bacillusthuringiensis Dipel,Delfin,Agree B.t.subsp.kurstaki Canola,brassicavegetablesGroup11A Bacillusthuringiensis Xentari B.t.subsp.aizawai BrassicavegetablesGroup13 Pyrroles Secure chlorfenapyr BrassicavegetablesGroup22A Oxadiazines Avatar indoxacarb BrassicavegetablesGroup28 Diamides Coragen chlorantraniliprole BrassicavegetablesGroup28 Diamides Belt flubendiamide BrassicavegetablesGroup28/4A Diamides/

NeonicotinoidsDurivo chlorantraniliprole&

thiamethoxamBrassicavegetables

Source:APVMA-PublicChemicalRegistrationInformationSystemSearch(PubCRIS),AustralianPesticides&VeterinaryMedicinesAuthority;accessedFebruary2016.

Tosummarize,althoughthereareapproximately170differentproductsfromtendifferentIRACMoAgroupsregisteredforthecontrolofDBMinAustralia,thereareonlytwosyntheticinsecticides(Group5spinetoramandGroup6emamectinbenzoate)andseveralBacillusthuringiensisvar.kurstakiproducts(Group11A)thatarecurrentlyregisteredforuseincanolaandcapableofreliablyprovidingefficaciouscontrolofDBM.Thesyntheticpyrethroid(Group3A)andorganophosphate(Group1B)productsaregenerallyineffectivebecauseofthesignificantresistancetoeachoftheseGroupsthatoccursinvirtuallyallDBMpopulations.ThestrategytomanagetheinsecticideresistanceriskassociatedwithDBMchemicalcontrolincanolapresentedinthispaper(Table5)onlyincludesthethreecurrentlyregisteredandeffectiveIRACMoAgroups,namelyGroups5,6and11A.

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Industrychemicaluseandsecondarychemicalexposure:TheDBMinsecticidecontrolpracticespresentedinthispaperarebasedonphonesurveysofagronomistsinSA,WAandVICandthepriorknowledgeoftheseniorauthor.DBMoutbreaksaresporadic.Theyvaryinfrequencybetweencanolagrowingregions,fromoneineverytwotothreeyears(eg.SWEyrePeninsulaofSA,northernwheatbeltofWA)tooneinfiveormoreyears(e.g.cool,highrainfallzonedistrictsofVictoria).Theregionsthatexperiencethemorefrequentoutbreaksaregenerallyinthewarmer,drierrangeofcanolaproduction,andtheseoutbreaksareoftenassociatedwithsummer-autumnrainsthatsupportgrowthof‘wild’brassicasandearlysowing.InyearswhenadistrictexperiencesaDBMoutbreak,typically50%ormore(attimesupto95%)ofthecanolacropinthedistrictwillbesprayedforDBMcontrol,usuallyoncebutoccasionallytwice.MostDBMsprayingoccursinearlytomid-springduringfloweringandpodformationandfilling,butonoccasionspraytreatmentsarerequiredtoprotectestablishingcropsfromdefoliationresultingfromearlyDBMbuild-up.Untiltheregistrationoftwonewchemistriesin2012(Affirm®andSuccessNeo®),thechoiceandusageofinsecticidesforDBMcontrolwerealmostuniversallyarangeofsyntheticpyrethroid(SP)products,withoccasionaluseofseveralorganophosphatesandBacillusthuringiensisvar.kurstaki.OverthepastdecadecanolagrowersandagronomistshavefoundthatSPtreatments,eitheraloneorinOP-mixtures,donoteffectivelycontrolDBM.Hencesince2012SPusageforDBMcontrolhasbeenlargelyreplacedbythenewly-availableAffirm®(Group6emamectinbenzoate),whichhasthemarketadvantageofbeingpricedsubstantiallylowerthantheothernewproduct,SuccessNeo®(Group5spinetoram).ItappearsthatonlyafewpercentofDBMcanolaapplicationsnationallyareSuccessNeo®orBtvar.kurstakiproducts.Btvar.kurstakiproducts,whichareanintermediatepricebetweenthetwonewsyntheticinsecticideproducts,aregenerallyoverlookedbyagronomistsandgrowersbecauseoftheperceptionthattheyarelessefficaciouscomparedtoAffirm®.ChemicalusageagainstDBMinAustraliancanolaistypicallywithinlabelrecommendationsandusuallyonlyappliedonacase-by-casebasisfollowingsweep-netmonitoringandreferencetoETguidelines.

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Table3.CurrentstatusofinsecticideresistanceindiamondbackmothwithinAustraliaAttribute Whatisknown? References KnowledgegapsResistancestatus • Confirmedwidespreadandhigh-levelsofresistancetopyrethroids

(Group3A)acrossAustraliancanolaandvegetableproductionregions.

• Confirmedwidespreadandmoderatelevelsofresistancetoorganophosphates(Group1B)acrossAustraliancanolaandvegetableproductionregions.

• Low-moderatelevelsofresistancetoemamectinbenzoate(Group6)andseveralGroup28insecticidesarecommonacrossAustraliancanolaandvegetableproductionregions.(TheGroup28resistancedetectedinDBMincanolacropsisnotablegivennilcanolausage.)

• Nil/incipientresistancetospinetoram(Group5),indoxacarb(Group22A)andBtvar.kurstaki(Group11A)inAustraliancanolaproductionregions.

BakerandKovaliski1999;Endersbyetal.2011.G.Baker,K.Powis(unpubl.data).

• Currentextentofresistancetonewchemistries(Groups5,6,13,22Aand28)invegetableproductionareas.

ModeofActionofresistance&cross-resistance

• Syntheticpyrethroids:mutationsinthepara-sodiumchannel(atkdr,skdrlandcdrloci,whichcausetargetsitemodification)isthemainresistancemechanism.Metabolicresistance(probablyenhancedactionofcytochromeP450oxidases)isalsoevident.

• Organophosphateresistanceprobablymetabolic.• Group6and28resistanceprobablymetabolic,withpossiblecross

resistancecomponent.

N.Endersbyetal.(2011).G.BakerandK.Powis(unpubl.data).

• Possibilityofmetaboliccross-resistancebetweenGroups3A,1B,6and28.

Knownfitnesscosts • FieldobservationsandEndersbystudy(whichreportedstablelevelsoffieldresistanceovertime)suggestnomarkedfitnesscostsassociatedwithSPtargetsiteresistance.

• ModestfitnesscostsassociatedwithGroup6and28metabolicresistanceinlab.

N.Endersbyetal.(2011).G.BakerandK.Powis(unpubl.data).

• Assessmentoffitnesscosts.

Geneticbasisforresistance

• Syntheticpyrethroids:notfullyresolved,butmayinvolveheterozygous(skdrl/cdr)fitnessadvantage.Thiswouldhelp

• Geneticbasisofresistancetoothermodeofaction

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maintainbothresistantallelesinpopsrepeatedlyexposedtopyrethroidspraying,especiallyifthereisafitnesscostassociatedwitheitherhomozygote.

groups.

Originofresistance • SPandOPresistancelikelytohaveresultedfromgene-flowfromvegetablesandfromlocalselectionduetograincropSP/OPusepatterns.

• Poorcoverageanddistributionoflarvaethroughoutthecanolacanopycommonlyresultsinsub-lethaldosing,whichmayexacerbatesurvivorshipofresistant(heterozygote)individuals

• SelectionpressureforresistancetothenewDBMinsecticides(Groups5,6,13,22A&28)isconsideredlowingrainsbecauseof:

o thelowDBMsprayfrequency(lowoutbreakfrequency,lownumberofsprays/canolacropinoutbreaks),and

o nil/minimalotherregisteredusesincanolaandothergraincrops.

• HenceresistancerisktothesenewDBMinsecticidesmaybemoredependentonnon-grainusepatterns(brassicavegetablesandforagecrops).

• Gene-flowbetweencanolaandotherbrassicacrops(vegetables,forage).

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Resistancemanagement&minimisationstrategyThebasisofthisstrategyistominimisetheselectionpressureforresistancetothesamechemicalgroupacrossconsecutivegenerationsofdiamondbackmoth(DBM)asaresultofDBMchemicalcontrolincanolacrops.ThestrategyincludesthreeDBMchemicalgroups-thetwosyntheticinsecticidesAffirm®(Group6)andSuccessNeo®(Group5)andthebiopesticideBacillusthuringiensisvar.kurstaki(Group11A)-eachofwhichprovideefficaciousfieldcontrol.Itexcludestheoldsyntheticpyrethroid(Group3A)andorganophosphate(Group1B)productsbecauseresistancetotheseproductsisubiquitousinAustralianDBMpopulationsatlevelsthatrenderthemineffective.‘Area-wide’adherencetoawindowstrategyislikelytobeasignificantchallengewhilelargecostdiscrepanciesbetweenthethreeavailablechemicalgroupscontinuetodrivegrower’schoices,particularlyduringoutbreaks.GiventhatthesusceptibilitytoBtkinscreenedAustralianDBMpopulationshasnotdeclineddespitethe45yearhistoryofBtkregistrationforDBMcontrolinAustraliancanola,vegetableandforagecrops,theresistancerisktoBtkproductsisconsideredtobelow.Group5insecticideswerefirstregisteredforcontrolofDBMinAustralianvegetablescirca1999-2000,andtheSuccessNeo®registrationwasextendedtoincludecanolaandforagecropusein2012;howeveronlyincipientshiftsinsusceptibilitytospinetoramhavebeendetectedthusfarinDBMcollectedfromcanola(upuntil2015)orvegetables(upuntil2010),andgiventhecurrentlowusepatternforSuccessNeo®inAustraliancanolatheresistancerisktoSuccessNeo®asaresultofcanolauseislikewiseconsideredtobelow.HoweverthereisadetectableshiftinsusceptibilitytoAffirm®inAustralianDBMpopulations,andhenceitisthisGroup6insecticidethatispresentlyconsideredatgreatestriskfromresistancedevelopment.TherelativecontributionsofselectionpressureonAffirm®fromitsuseincanola,versusGroup6useinvegetableproduction,versusmetaboliccross-resistanceconferredfromtheuseofotherpesticides,remainsunknown.DBMappearstobeaseasonalmigrantinAustralia.Thereis(limited)evidenceofspringmigrationsofDBM;further,resistanceprofilesofDBMcollectedfromweedyhostsandcanolacropsrevealsimilarinsecticideresistancepatternsonbothhostsourcesandacrosslargegeographicranges,andgeneticmarkerstudieshaverevealedlittlegeneticdifferentiation,eachsuggestingthataconsiderabledegreeofinterbreedingandgeneflowisoccurring.DBMover-summeronirrigatedbrassicavegetableandforagecropsandpatchesofrain-fedbrassicaweedsandvolunteercanola.HoweverthesourcesoftheDBMthatcolonizewinter-sowncanolaarenotdefined.DoessignificantDBMgene-flowfromvegetableandforagecropstocanolacropsoccur?Subjecttotheanswertothisquestion,insecticideselectionpressuresonDBMinvegetable(andforage)cropsmayhavesignificantbearingonthetrajectoryofinsecticideresistancetothenewerchemistriesinDBMpopulationsthatcolonizecanolacrops.AndhencethecapacityofthisproposedresistancemanagementstrategytolimitthedevelopmentofinsecticideresistanceincanolapopulationsofDBMinfutureyearsmaybeasdependentonDBMmanagementpracticesinvegetable(andforage)cropsasitwillbeoncanolagrowercompliancewiththestrategy.TheincorporationofIPMstrategiesforDBMmanagementincanolaisintegraltounderpinningareductioninDBMinsecticideuseandtherebyhelpingtominimizeresistanceselectionpressuresincanolacrops.

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Finally,thereisclearlyaneedfornewchemicaloptionstocontrolDBMinAustraliancanolacrops,asthelimitedoptionscurrentlyavailabletogrowersmakeitdifficulttousethealternationofchemicalgroupsforlong-termresistancemanagement.

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ResistanceManagementStrategyforDiamondbackMoth(DBM)inAustralianCanola

INTRA-SEASONMANAGEMENT

1. Summer-Autumn:Pre-seasonSummerrainfalleventscangeneratebrassica‘green-bridge’growth,whichcansupportDBM(e.g.volunteercanola,Lincolnweed,etc.).

Inyearswhenthebrassicagreen-bridgeisabundantandextendsthroughMarch-AprilthereisahigherriskofearlierandgreaterDBMcolonizationofcanolacrops,requiringincreasedattentiontoearlycropmonitoring.TheDBMriskassociatedwithsummer-autumngreen-bridgemayalsoextendtohigherDBMpopulationsintheearlyspring.IndistrictsthatexperiencefrequentDBMoutbreaksandyear-to-yearcarryoverofDBMpopulationsonlocalgreen-bridgegrowth,area-widegreen-bridgecontrolhasthepotentialtobenefitDBMmanagement.

2. CropStage:Pre-floweringMonitorat3-4weekintervalsfromestablishmentusingeithervisualinspection(uptotherosettestage)orasweepnet(stemextensiononwards).Seesweepnetmonitoringinstructionsbelow.

MorefrequentmonitoringisadvisedinyearswhentheDBMriskisgreater,namelyyearswithsubstantialgreen-bridgeoversummerandwhendryconditionsand/oraboveaveragetemperaturesoccurduringautumnandwinter.

Grazing+Grain:WherepossiblemanageDBMfoliarfeedingbystrategicgrazing.

IfunabletointroducestocktomanageDBM,applyaBtsprayabiftheeconomicthreshold(ET)isreached(refertoThresholdstablebelow).

(Notethatthesamerecommendationsapplyforforagebrassicas.)

Grainonly:Iftheeconomicthreshold(ET)isreachedapplyaBtsprayab.

3. Crop-Stage:Flowering/Podding(GrainonlyandGrazing+Graincrops)Monitorcropsusingasweep-netatfortnightlyintervalsthroughoutfloweringtowindrowing/harvest(morefrequentlywhenweatherdryand/ortemperaturesareaboveaverage).

Sweep-netmonitoringinstructions:Takeaminimumof5setsof10sweepsinseveralrepresentativepartsofthecropandcalculatetheaveragenumberofthelarvae(caterpillars)per10sweeps.InadditiontoscoringtheDBMlarvae,record

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thenumbersoflarvaeofothermothpests(eg.nativebudworm,cabbagecentregrub)andthenumbersofDBMnaturalenemies(Seenaturalenemytable).

IftheDBMETisreached(refertotheThresholdstablebelow)aspraytreatmentisrecommended.

Sprayproductchoice:

i)IfcontrollingDBMalone,applyaBtc,AffirmdorSuccessNeodspray.

ii)IfcontrollingDBMandHelicoverpalarvaethatarelessthan8mmlength,applyaBtce,BtplusVivusMaxe,AffirmdorSuccessNeodspray.

ii)IfcontrollingDBMandHelicoverpalarvae*greaterthan8mmlength,applyeitheranAffirmeorSuccessNeoespray.

*HelicoverpaET:4-5larvaeper10sweeps.

NotegoodspraycoverageisessentialforachievingeffectivecontrolofDBM,andbecauseofdensecanolacanopiesinspringrequireappropriatenozzletype,pressureandvolumesf.

ContinuetomonitortheDBMpopulationandnaturalenemyactivitypostspraying.

IntheunlikelysituationthattheDBMpopulationagainincreasestotheETdensity,avoidconsecutiveuseofthesameproduct.E.g.UseSuccessNeoifAffirmwasappliedearlier,orviceversa.

INTER-SEASONMANAGEMENTIfDBMoutbreaksthatwarrantspraytreatmentoccurinconsecutiveyears,inthesecondyearavoidusingthesameproductusedinthepreviousyear.

InsecticideProductExplanatoryComments:aBtproductswillconservebeneficials,whichisparticularlyimportantearlyseason.Forwinter-sowncanolaBtproductsaresuitedtotherelativelylowUVconditionsthatprevailduringpre-flowering.Also,Btproductsbenefitfromthegreatereaseofcoverageassociatedwiththelessercanopyareaofpre-floweringcrops.Wethereforerecommendduringpre-floweringtonotusethetwocurrently-availablechemicalinsecticides,AffirmandSuccessNeo,andinsteadreservingthemforuseduringflowering-poddingifrequired.

bInsomesituationspre-floweringcropsareinfestedbyverydenseDBMinfestations,andahigherlevelofcontrolmayresultfromtheuseofachemicalinsecticideratherthanaBtproduct.IntheseinstancesinfodderbrassicacropsSuccessNeoistheonlyregisteredchemicalproduct.Ingraze+graincanolacropsSuccessNeomaybepreferredbecauseithasshortergrazingWHP(7day)thanAffirm(14days),andthereforemoresuitableiffurthergrazingmayberequiredinashortperiodoftime.IngraincropseitherAffirmorSuccessNeoisrecommendedforuseinthesesituations.

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cBtproductswillconservebeneficials,butarelesssuitableiftheDBMlarvaldensityisrapidlyincreasingabovetheET.IfaBtspraywasappliedearlierduringpre-flowering,therationaleforadvisingarepeatuseofaBtsprayratherthananAffirmorSuccessNeosprayistoavoid‘flaring’DBMandotherpests(e.g.aphids),andbecausethisrepeatBtspraystillpresentsalowresistanceselectionriskgiventhelowfrequencyofDBMoutbreaksinAustraliancanola.

dAffirmorSuccessNeoareconsideredmoresuitablefortreatmentofrapidlyincreasingDBMpopulations,astheyeachhavegreaterpersistenceunderfieldconditionsinspringcomparedtoBtproducts.HoweverbothAffirmandSuccessNeoaretoxictoparasitoidwaspsandnabidpredatorybugs,andhighlytoxictobees(followthe‘ProtectiontoHoneyBees’guidelinesonthelabel).

eBtproductsrequireoptimalconditionsandsmall-sizedlarvae(nogreaterthan8mm)fornativebudwormcontrol.AmixtureofBtandVivusMaxisabiologicalpesticideoptionfornativebudwormcontrol.

fToachievethenecessarycanopypenetrationandcoverageforlateseasonDBMcontrolusewatervolumesofnolessthan100L/ha(groundapplied).Air-inductionnozzlesorflatfannozzlesgreaterthan110-03,spacedat50cm,producingamediumsprayqualityhaveprovidedgoodcontrolofDBMincanolacropsandreducedriftwheneffectiveproductsatlabelratesareused.

Syntheticpyrethroid(SP)andorganophosphate(OP)productsarenotrecommendedforDBMcontrolatanycropstage,becauseresistancetotheseproductsiswidespreadinAustralianDBMandresultsinpoorcontrol,typically20-30%controlwithSP’sand30-50%controlwithOP’s.Notethatbecauseoftheirbroad-spectrumactivity,SPandOPspraysforthecontrolofothercanolapests(e.g.aphids)willkillmostnaturalenemygroups,andhenceincreasetheriskofflaringaDBMoutbreak.

ThecarbamatemethomylisregisteredforDBMcontrolinWesternAustraliancanola;whilethereisnocarbamateresistancedataavailableforAustralianDBM,OP-carbamatecross-resistancehasbeenreportedinoverseaspopulationsofDBM.

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EconomicThreshold(ET)Table:Cropstage Moisturestress DBMthreshold

Rosette* N 50%leafareadamagedPre-floweringstemextension Y 30larvaeper10sweepsPre-floweringstemextension N 50larvaeper10sweepsEarlytomid-flowering* N >50larvaeper10sweepsMidtolate-flowering* N >100larvaeper10sweepsPodmaturation* N 200larvaeper10sweeps*Moisturestressisnotlistedforthesegrowthstages,butnotethatmoisture-stressedcropsare more susceptible to insect damage. A lower threshold may be used if extended dryperiodsareexpected.(Source:adaptedfromGRDCDiamondbackmothFactSheet)

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CommonNaturalEnemiesofDBM:Group Whattolookfor? ImpactonDBMParasitoids Theadultwaspparasitoidsaresmall(3-5mm).The

mainspeciesisDiadegma(seephotoofadult).

NotetheunparasitizedDBMpupaearetapered(upperphoto)andeasilydistinguishedfromtheparasitizedDBMpupae,whicharecapsuleshaped(lowerphoto).

DiadegmawaspslayeggsinthesecondinstarDBMlarvae,killthehostandemergefromtheircocoon.Parasitismof40-60%isoftenobserved,andcansignificantlyreduceDBMdensities.

Lacewings Brownlacewinglarva.

Contributetosupressinglow-moderateDBMpopulations.WillfeedonDBMeggs,larvaeandpupae.

Ladybirds BothladybirdadultsandlarvaeattackDBM

Contributetosupressinglow-moderateDBMpopulations.

Spiders Numerousspeciesofspidersinhabitcrops.

Willfeedoneggs,larvae,pupaeandadults

Damselbugs

Adults(left),winglessnymphs(right)feedoneggs,larvae,pupaeandadults

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Fungaldisease

DBMlarvaekilledbyZoophthorafungaldisease

OutbreaksofthefungaldiseaseZoophthoraradicanscancausegreaterthan90%reductioninDBMpopulationdensityfollowingaperiodofwarmtemperatures,rainfallandhighhumidity.Diseasedlarvaebecomeyellow,sluggishandswollenbeforedying.Deadlarvaearewhite,brittle,flatandcoveredwithfungus.

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Generalprinciplestoavoidorminimiseresistancedevelopment:

• AvoidrepeateduseofinsecticidesfromthesameIRACmodeofactionchemicalgroupagainstDBMorotherpests,asthiswillincreaseselectionpressureforresistancedevelopment,notonlyinDBMbutotherspecies;

• Wherepossible,avoiduseofSP’sandOP’sforcontrolofspringpests,andinsteadusetarget-specific“softchemicals”suchaspirimicarbforaphidsandBtforcaterpillars;

• Ensurethetargetpestiscorrectlyidentifiedtoensurethemosteffectiveinsecticideandrateisused.Misidentificationandincorrectinsecticideselectionresultsinpoorcontrolandcontributetoselectionforresistance;

• AssessDBMandbeneficialpopulationsbyfortnightlysweep-netmonitoringtodetermineifchemicalcontroliswarranted.Usespraythresholdstoensurespraydecisionsarewarranted;

• Donotre-sprayacropinthesameseasonwhereaknownsprayfailurehasoccurredusingthesameproductoranotherproductfromthesameinsecticidegroup,orifasprayfailurehasoccurredwherethecausehasnotbeenidentified;arrangeforaDBMsampletobetestedforresistancetotheproductused;

• Complywithalldirectionsforuseonproductlabels;• Ensuresprayrigsareproperlycalibratedandspraysachievegoodcoverage,

particularlyincropswithabulkycanopy;• Ifgrowingforagebrassicas,manageDBMbygrazingoruseofBtk.

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