northern iwm fact sheet - department of agriculture and ... iwm fact sheet ... prolonged use and...

Northern IWM fact sheetFeathertop Rhodes grassA weed best management guide

Figure 1. Fallow paddock heavily infested with feathertop Rhodes grass. Chemical control at this growth stage can be very difficult

Figure 2. Feathertop Rhodes infestation in sorghum in Central Queensland

CS1437 03/12

Key messages

• FeathertopRhodes(FTR)grassrequiresanintegratedandintensivemanagementapproach;therearenosilverbulletsforeasymanagement.

• Seedsetmustbestoppedorminimisedtobreakthelifecycleandreducefutureweedburdens.• Largeweeds(>10cm,tilleringorwithseedheads)areverydifficulttokillwithknockdownherbicides.• Small,activelygrowingweeds(<5cm,pre-tillering)shouldbetargetedwhenusingpost-emergence

herbicides.• Thedouble-knocktacticisveryeffective,particularlywithaGroupAherbicidefollowedbyaGroupL

herbicide.Theknockintervalshouldbeatleast7daysformaximumeffectiveness;addingresidualherbicidestothesecondknockmayimprovetheGroupLknockdown.

• Theeffectivenessofpre-emergenceherbicides(residuals)canbemaximisedbyapplyingthemwhenthesoilsurfacehasverylittleornoweedcover.

• Escapesandsurvivorsshouldbemonitoredandspottreatedassoonaspossible.• Strategictillage,toburyseedorcontrollargeplants,hasaroletoplaybutmaynotsuitallsituations.• Competitivecropsandcultivarsshouldbeplanted,andnarrowrowspacingsandhighcrop

populationsusedwherepossible.• Cropsthatallowtheuseofthegrass-activeGroupA(‘fops’and‘dims’)herbicidesofferalternatives

toglyphosateandallowforherbicidegrouprotation;thefopsappeartobetterthanthedims.• Cropsshouldbeplantedintoweed-freesoilandpre-emergenceherbicidesused.Weedsshould

betreatedin-cropwithpost-emergenceherbicides(over-the-toporshieldedboom)orinter-row tillageifrequired.

Feathertop Rhodes grass: a weed best management guide 2

Where and why is feathertop Rhodes grass a problem?

FeathertopRhodes(FTR)grassisamajorweed inbroadacrecroppingsystemsinCentral Queensland(CQ),theDarlingDownsandWesternDownsregionsofsouthernQueensland,andinnorthernNewSouthWales.ArecentscopingstudyofcoastalandnorthernQueenslandcroppingrevealedFTRtobeamainweedinthosefarmingsystemsaswell.InterstateinquiriesindicateitisalsoaprobleminthevineyardsandorchardsofSouthAustralia,andinpartsoftheWesternAustraliangrainregion.FTRhasprovenverydifficulttocontrol.

Previouslyaweedofroadsides,fencelinesandwastelandareas,FTRhasnowbecomeanissueincroppingcountry,particularlywhereminimumorzerotillagehasbeenpracticedforseveralyears.Itisnotoverlysusceptibletoglyphosateherbicide,particularlyaftertheearlytilleringstage.Theprolongeduseandrelianceonglyphosateinthefallowsofthesecroppingsystemshasassistedwithaspeciesshifttowardsthisgrass.Forthesamereason,FTRhasalsorecentlybecomeanissueinglyphosate-tolerantcottonsystems.Withminimaldisturbance,theseedremainsintheuppersoilsurface,whichisidealforemergenceandperpetuationoftheweed.Dryconditionshavemademanagementdifficult,allowingseedbankbuild-up.Verywetseasonshavebeenassociatedwithsubstantialfieldpopulationincreases.WhileFTRhasapreferenceforlightertexturedsoils,itwillalsosurviveonheavierclaysoils.

Know the enemy

Description

FTR(Chloris virgataSw.)isatuftedannualgrassupto1mtallwitherectandsemi-prostratebranchedstemscapableofrootingatthejoints.Leafbladesarebluishgreen,5to25cmlongand3to6mmwide.Theseedheadsorpanicleshave7to19feathery,white-silverspikesthatare3to9mmlong.Thefeatheryappearancecomesfromthestiffwhitehairsandawnsarisingfromtheseeds.UnlikecommonRhodesgrass,FTRpaniclestendtoremainunsplayedandpointingupwards.Seedlingsareerectbutwithflattenedstembases,andthisflatteningbecomesmoreobviousinoldertillers.Leafbladeshavetufts

ofhairsalongthemarginsandwherethebladejoinsthesheath.Thestemjointsarehairlessandsometimesverydark.Intheearlygrowthstages,FTRcanbeeasilyconfusedwithawnlessbarnyardgrass(Echinochloa colona).

Figure 3. Early tillering FTR plants (approximately 5 cm tall).

Note the stem bases have a flattened appearance

Figure 4. Mature FTR plants

Seed behaviour

Beinganannualinmostsituations,FTR’sdynamicsaredriventhroughtheseed.Managetheseedproductionandrecruitment,andeffectivecontrol willeventuate.

CQresearchtrialsandgrowthcabinetstudiesexamininggermination,fieldemergence,persistence(viabilityanddormancyovertime)andtheeffectofburialdepthonfreshFTRseedhaveshownthat:

Feathertop Rhodes grass: a weed best management guide3

• Germinationoccursacrosstemperaturesof 20to30 °Cbutapreferenceisshownfor25 °Candabovewithexposuretolight.

• Seedhasaninnatedormancy,requiringanafter-ripeningperiodofapproximately6to10weeks.Whilepre-chillingassistsinbreakingdormancy,itisnotessential.

• Approximately25%ofseedproducedisnon-viable(deadorincomplete),butthismayvaryandbeinfluencedbygrowingconditionsbeforeandatseedmaturation.

• Seedappearstobeshort-lived(about7to12months)irrespectiveofburialdepth,suggestingshortfieldpersistence(Figure5);seedexhumed

fromdepthafterbeingburiedfor12monthsdidnotgerminateevenafterseveraldormancy-breakingmechanismswereapplied.

• Themajorityoffieldgerminationsoccurfromthe0to2cmseedburialdepth;over12months47%ofseedburiednearthesurfacegerminated,comparedwith5%at5cmand0%at10cmdepths.

• Thecumulativegerminationoftheseedbankatornearthesurfaceovera12to18monthperiod(totalrecruitmentoremergence)rangedfrom25%to50%inthreeseparatestudies,withthemajorityoftherecruitmentoccurringwithinthefirst7months(Figure6).

Figure 5. FTR seed bank viability over time in the CQ environment

Figure 6. Cumulative in-field emergence of FTR (expressed as a percentage of the seed bank) from seed buried in the surface

2 cm of soil (studies 1 and 2 used seed from the same source; all studies started at the end of summer)

00

20

100

80

60

40

2 6

Time after seed burial (months)

% v

iabl

e FT

R se

ed(in

rem

aini

ng s

eed

bank

)

12 18

10

20

10

60

50

40

30

52 10

Seed burial (months)

Cum

ulat

ive

in-fi

eld

FTR

emer

genc

e(%

of s

eed

bank

)

15 18 1916 1713 14

study 1

study 2

study 3

11 128 96 73 4


Implications for management

BepreparedandconsiderthefollowingwhendevelopingamanagementplanforFTR(basedonCQresearch):

• FTR’sveryshalloworsurfacegerminationrequirementmeansitwillmostlikelybeaprobleminzero-tillpaddockscomparedtodisturbedpaddocks.

• FTRislikelytogerminateyear-roundinCQbutwithpreferencefortheperiodbetweenspringandautumn.MildwetwinterswillalsoproducerecruitmentsinCQ.

• Thereshouldbelimitedimmediaterecruitmentfromfreshlyshedseedduetotheafter-ripeningrequirement,althoughtheconditionofthemotherplantduringseedsetmaydeterminedormancylevelsandafter-ripeningrequirements.

• Seedshedduringlateautumnwillreceiveimmediatepre-chilling(goingintowinter)thusbreakingdormancyandallowinggerminationonthefirstspringrains.

• Buryingtheseeddeeperthan5cmandleavingitdeepandundisturbedforatleast12monthswillstopseedlingemergenceandwillsignificantlyreducetheseedbankastheviabilityofseedsdeteriorates.

• Ifseedsetisstopped(nofurtherdepositsaremadeintotheseedbank),FTRproblemsshouldbediminishedquicklysincetheexistingseedbankisshort-lived.

Repeatedfieldobservationssuggestthatpeakormajorflushesofemergenceoccurifgoodrain(>50 mm)fallsoverseveralconsecutivedays,particularlyinspring.Thesemajorflushescanexhaustthemajorityofthenon-dormantviableseedbankandofferanidealmanagementopportunity.Sporadicandsmallerraineventsfacilitateanumberofsmallersequentialgerminations,makingeffectivecontrolviaasinglemanagementapplicationmoredifficult.

Figure 7. A germinating FTR seed

Figure 8. Peak flushes of FTR, just after emergence (top), and

well established in close proximity to senesced mother plant

(bottom)


Management strategies

ResearchandindustryexperiencehaveshownthatsuccessfulmanagementofFTRrequiresanintegratedapproach,withattentiongiventobothfallowandin-cropphases.Importantmanagementconsiderationsandprinciplesthatapplyacrossallfarmingsystemphasesincludethefollowing.

• NosingleweedmanagementapplicationwilleffectivelycontrolFTR—useavarietyoftacticsincombinationandovertime(acrossrotationphases).

• Aimtostopseedsettohalttheperpetuationofthisgrassproblem.• Usethedensityanddistributionacrosspaddockstodeterminetreatmenttype—boom,spotsprayer,

aerial,orexpansiveversusspottillage.• ForscatteredoroccasionalFTRinfestations,makeaconcertedefforttopreventthesefrombecoming

biggerproblemsusingwhateverspottreatmentisnecessaryoravailable.• Targetsmall,non-stressedandactivelygrowingplantstoimprovethechancesofgoodcontrol.

SprayingsmallFTRseedlingsassoonaspossibleafterrainislikelytoprovidebestcontrol,andaerialapplicationshouldbeconsideredifitstaystoowettousegroundsprayers(asthesoilprofiledries,plantstresslevelsincrease).

• Usegoodherbicideapplicationtechniquestomaximisecoverage—appropriatenozzles,boomheights,watervolumesandspeedfortheintendedsprayjob.

• Closelymonitortheresultsofallmanagementapplicationsandspottreatsurvivorsassoon aspossible.

• Whenusingresidualherbicides,thesoilsurfaceneedstohavelessthan50%weedorstubblecover.Ideallynoweedsshouldbepresenttomaximisetheamountofherbicidereachingthesoilsurface.

• Ifusingtillagetocontrolexistingplants,ensurethedepthandtypeoftillageissufficienttouprootthegrasswithoutsubsequentlytransplantingit.Therootingdepthwilldependontheseason—rootswillbeshallowindryseasons.

• Ifusingtillageforseedburial,ensurethedepthofsoilinversionisatleast10cmtoguaranteeburialbelowthedepthatwhichtheweedcangerminate.

• Manageoutbreaksalongroads,fencesandaroundshedsasthesewillbeacontinuingseedsource forpaddocks.

Herbicide registrations

ThefewherbicidesspecificallyregisteredforthecontrolofFTRareatrazine,butroxydim(e.g.Factor®),clethodim(e.g.Select®)andArsenalXpress® (imazapyr+glyphosatefornon-croplandusesonly),whileclorthal-dimethyl(Dacthal®)isregisteredforcontrolofChlorisspp.incotton.Paraquat(e.g.Gramoxone®)hasaregistrationforcontrolofannualgrassesingeneral.

Arecent‘minoruse’permithasbeenissuedtocoverFTRcontrolinfallowspriortomungbeancroppingusingthedouble-knocktechnique(permit12941).Itallowshaloxyfop520gai/Lformulations(e.g.Verdict® 520)tobeappliedat78to156gai/hawithUptakeTMsprayoiladditive(0.5%v/v)whichthenmustbefollowed7to14dayslaterwithparaquat(e.g.Gramoxone®)appliedat400gai/haonto3-leaftoearlytilleringFTRgrowingonfallowlandthatwillbenextcroppedtomungbean.

CQresearchoverthepast6yearshasdemonstratedseveralpromisingherbicidesforthecontrolofFTRbothinfallowandin-crop.Whilethemajorityoftheherbicidesareregisteredforuseintherespectivesituations,theydonotcurrentlyhaveFTRlistedontheirlabels.CurrentdevelopmenttrialsbeingundertakenbytheregionalGrowerSolutionsgroupswillsupplyfurtherdatatosupportnewFTRregistrations.

Control tactics

ToeffectivelycontrolproblemweedssuchasFTR,allphasesofthelifecyclemustbeattackedusingarangeofchemicalandnon-chemicalmethods.Theaimistodepletetheseedbank,controlseedlingsandsmallplants,stopseedsetandpreventnewseedsenteringfromoutsidethesystem.


Seed bank depletion

Residual herbicides (fallow and in-crop)FallowandcroprotationtrialsinCQhaveshownseveralresidualherbicidestobeveryeffectiveonFTR.Forin-cropsituationstheseresidualswereappliedeitherpre-plantduringthefalloworpost-plantpriortocropemergence.Infallow,theywereappliedaloneoraspartofadouble-knockstrategy,withbestresultsmostoftenoccurringwhenappliedwithaGroupLbipyridylherbicideinthesecondknock(weedcoverhasbeenreducedbyfirstknockandtheGroupLofthesecondknockassistswithrapidplantmatterdesiccationanddisintegration).

Theresidualherbicidesactonthegerminatingseedsofsequentialflushes,oftenstoppingestablishmentandthusdepletingtheseedbankaseachcohortattemptstoemergeorestablish.Thenumberofcohortsaffected(lengthofresidualactivity)isdeterminedbytheherbiciderateapplied,soiltype,theensuingclimaticconditionsandlocationoftheseedrelativetotheherbicide(root/shootaccessibility).

Whenusingresidualsitisimportantthattheherbicidesreachthesoilsurface,soapplicationisbestmadetobaresoilthatisweedandstubblefree.Rainshouldbereceivedwithin14daysofapplicationtoallowincorporationbelowthesurfaceintotheseedzoneandtominimisetheamountlosttoultravioletdegradation.Thebesttimetoapplyispriortothesowingrain(herbicidewillcontrolFTRplantsemergingwiththecrop).Applyingimmediatelyaftersowingisanalternative,butthistendstobelesseffectiveiffollow-uprainisnotreceivedsoonafter.Applicationwatervolumesshouldbekepthigh(80to100L/ha)forbestresults.Re-croppingopportunitiesmaybelimitedwhereresidualshavebeenusedsoconsultherbicidelabelstodeterminetheplant-backperiods.

FallowEffectiveresidualsappliedinthefallow(oftenaspartofadouble-knockstrategy)haveincludedaGroup CtriazinemixedwithaGroupKchloroacetamide,andaGroupBimidazolinone(seeTable1).SixyearsofCQresearchdataonFTRhavealsoshownthattheGroupCandKherbicidesaremoreeffectiveandlong-lastingwhenmixedtogetherthanwheneitherisappliedalone.Thesameresearchhasshownthatwhentheseherbicidesareappliedinfallowsduring

thecoolermonths,thedurationofcontrolisseveralmonthslongercomparedtofallowuseinsummer.

In-cropTheFTR-effectiveresidualherbicidesappliedimmediatelypre-plant,atplantingorpost-plantpre-emergenceinCQresearchtrialshaveincluded:

• sorghum:GroupCtriazine+GroupKchloroacetamide

• wheat:GroupBsulfonylurea;GroupKchloroacetamide;GroupDdinitroaniline(see Table1)

• chickpea:GroupKchloroacetamide;GroupCtriazine+GroupFisoxazole

• mungbean:GroupDdinitroaniline;GroupB(1)and(2)imidazolinones(seeTable1)

• sunflower:GroupCtriazine;GroupD(1)and(2)dinitroanalines;GroupKchloroacetamide(seeTable1).

Alloftheseherbicidesareregisteredforuseintherespectivecrops(exceptGroupB(2)imidazolinoneinmungbean)butnotforthecontrolofFTR.Furtherdevelopmentworkwiththeseherbicidesiscontinuing.

Strategic tillage alone or in combination with residual herbicides (fallow)SinceFTRgerminatesatorverynearthesoilsurface,buryingtheseedbelow5cmwillplacetheseedtoodeepforgermination.Strategictillagecanbeusedtodothis,andCQresearchhasshownthatdeepinversion(25cm)tillagecompletelystopsFTRemergencesforaslongas9monthsafterimplementation.Othertillagetypesprovidedarangeofcontrolfrom1%to89%forthesameperiod.Applicationofaresidualherbicidewithtillagecanalsobebeneficialinreducingtheseedbank(seeFigure9).

HarrowsandKellychainscanbeusedto‘tickle’theupper5cmofsoiltocreateanidealseedbedforFTRgermination.SeveralfieldobservationshavebeenmadeinCQthatshowthesetickletillageoperationsfacilitatepeakflushesofFTRemergence.Theseflushesvirtuallyexhausttheseedbankandpresentexcellentopportunitiesforearlypost-emergencemanagement.


Figure 9. Impact of different tillage types, some with residual herbicides included, on the control of FTR at 9 months after

application after receiving > 200 mm rain

0

20

10

deep inversion

offset discs

scarifier

harrows

100

80

90

60

70

40

50

30

Tillage treatments

FTR

cont

rol (

%)

scarifier +

herbicidesze

ro till +

herbicides

Table 1. Impact of residual herbicides used in various crops on FTR dynamics measured in a replicated research trial at

Biloela Research Station

Crop and residual herbicide FTR reduction (%)

Wheat (50 cm wide rows)

noherbicides 72

GroupBsulfonylurea 100

GroupDdinitroanaline 94

GroupKchloroacetamide 91

Wheat (25 cm wide rows)

noherbicides 100

GroupBsulfonylurea 100



Sunflowers

GroupD(1)dinitroanaline 100


GroupD(2)dinitroanaline 100

GroupCtriazine 100

Mungbeans


GroupB(1)imidazolinone 100

GroupB(2)imidazolinone 100

noresidualonlypost-emergenceknockdowns 100

Fallow

double-knock:GroupMfollowedby GroupL+GroupBimidazolinone 100

3sequentialdouble-knocks(GroupMfollowedbyGroupL)withoutresiduals 100


Seedlings and small plant control

Post-emergence herbicides (in-crop and in fallow)FallowFTRdoesnotappearinthelistsofweedscontrolledonthelabelsofanyfallow-registeredknockdownherbicide.Howeverasnotedpreviously,minorusepermit12941allowsadouble-knockofVerdict®520(GroupA)followedbyparaquat(GroupL)butonlyinfallowsthatwillbeplantedtomungbean.

ResearchinCQhasshownthatonceFTRispastearlytilleringstage,aGroupM(glycine)herbicideusedalonebecomesineffective,butifaGroupLbipyridylherbicideisappliedsequentially,controlapproaches100%.Thisdouble-knocktactic(seeFigures10and11)hasprovedtobethemostconsistentlyeffectiveacrossarangeofgrowthstagesandplantstressconditions.Thesameresearchhasalsoshownthattheadditionofresiduals(particularlyGroupB)tothesecondknockenhancestheknockdownoftheGroup Lherbicide(Figure12).

Figure 10. Double-knock on FTR in fallow (Group M herbicide

followed 10 days later with Group L mixed with Group C

and K residual herbicides)

Figure 11. Untreated FTR (top) compared to the success of the

double-knock (Group M herbicide followed 11 days later by

Group L mixed with a Group B residual herbicide) (bottom)

Sincethedouble-knockisasequentialapplicationofherbicides,theintervalbetweenknocksisimportanttooverallefficacy.Formanyweeds,theintervalisshort(3to4days)butforFTR,aminimumof7daysisnecessarywhenusingaGroupMasthefirstknock.ThisisprobablyduetoanantagonismthatoccursinsidetheplantandisspecifictoFTR.ResearchconductedbytheNorthernGrowerAlliancediscoveredthisanomaly(Figure13),whichisbeinginvestigatedfurtherbyresearchersinthenewlyfundedGrainsResearchandDevelopment


Corporation(GRDC)project‘ImprovingIWMpracticesintheNorthernRegion’.

CurrentfieldtrialsconductedbytheCQGrowersSolutionsprojectareshowingthatthedouble-knocktacticofaGroupAherbicidefollowedbyGroupLwithresiduals(particularlyGroupB)isfarsuperiortothedouble-knockwhereaGroupMherbicideisappliedasthefirstknock.ThesetrialsarealsoshowingthatasFTRdensityincreases,therateoftheGroupAfirstknockneedstoincreasetomaintaingoodefficacy.

Ideally,aherbicide-baseddouble-knocktacticworksbestwhenappliedtosmall,activelygrowingweeds,andratesforbothknocksshouldbekeptrobust.Costsofthedouble-knockcanbereducedbyapplyingthesecondknockasaspotspray(densitydependent)orusingweeddetectiontechnologyifavailable.Spottillagemayalsobeanoption.Insomeinstancesthesecondknockmaybeatillageoperationinsteadofherbicide.

Figure 12. Impact of the residual herbicides (Groups K, C and B) with Group L in the second knock of a double-knock tactic on

the knockdown control of FTR. The first knock was a robust rate of a Group M herbicide. Data are the means of three CQ trials

Figure 13. Effect of time interval between the first (Group M herbicide) and second knocks (Group L herbicide) of the double-

knock tactic on control of FTR in a southern Queensland trial. The ‘0’ day treatment only received the first knock (data source:

Northern Grower Alliance)

75

85

80

100

95

90

Herbicide groups applied in the second knock

FTR

knoc

kdow

n co

ntro

l (%

)

L only L + K L + C L + C + K L + B

0

40

20

100

80

60

Time interval between knocks (days)

FTR

cont

rol (

%)

0 4 12 19


In-cropIn-cropmanagementofFTRwillbelimitedbythecropchosenandtheherbicidesthatcanbesafelyusedwiththosecrops.Forpost-emergencecontrolin-crop,shieldedsprayersmayberequired(GroupLandMherbicidesinmostcrops,andGroupAherbicidesinsomegrassandcerealcrops).Localresearchhasshownthatseveralofthegrass-selectiveGroupAherbicideshavegoodefficacyonFTR,andthe‘fop’chemistryappearstobetterthanthe‘dims’and‘dens’,althoughbutroxydimandclethodimaretheonlyGroupAherbicidesregisteredin-cropforFTRcontrol.

Thegrass-selectiveknockdownherbicidesarewidelyusedinthebroad-leavedcropssuchasmungbean,chickpea,cottonandsunflower(seeFigures14and15).GrowingthesecropsintherotationplaysanimportantroleinmanagingFTRandalsoinmanagingherbicideresistanceforotherhigh-risksummergrasses.TherearealsocertainGroupAherbicidesusedinwheatandbarleythatprovidegoodpost-emergenceefficacyonFTR,sowintercerealsshouldbeconsideredasanoptioninthedevelopmentofanintegratedweedmanagement(IWM)plan.

Figure 14. Group A herbicide applied in sunflower to

control FTR

Figure 15. Group A herbicide applied over the top of

mungbean to effectively control FTR

TillageCultivation,includinginter-rowtillage,isanalternativeoptiontocontrolemergedFTRinfallowsandin-crop.Howeverforthelatter,croprowsneedtobewideenoughandthecropshortenoughtofacilitatepassageoftheimplementswithoutsustainingdamagetothecrop.Inmanycasesinter-rowtillageisonlyanoptionintheearlycropgrowthstages.Tillageisbestperformedwhensoilconditionsaredrytoavoidthepossibilityoftransplanting.

SuccessoftillageforFTRcontrolduringthefallowhingesonplantsizeandtypeofcultivationundertaken.SmallFTRplantsareeasilyremoved,particularlyifmoisturestressedandshallowrooted,byKellychainsorsimilarequipment.Theexperiencesofafewgrowerssuggestthattheuseofafallowknockdownherbicidefollowedseveraldayslaterbyashallowtillage(anotherexampleofadouble-knocktactic)withaKellychainworksbestwhentheFTRisnolargerthantheearlytilleringstage.Asmentionedpreviously,tickletillagecanbeusedtopromotepeakflushesofemergencethatcanthenbetargetedwiththeherbicide-baseddouble-knocktactic.

WhenFTRplantsarelargeandclumped,tillagethatuprootsandchopsthematerialisbest—tandemoffsetdiscsandchiselploughsshouldbeconsidered.IfFTRdensitiesarelowandplantsarescattered,spottillage(e.g.asingle-tinedsweep)maybeaminimumtillageoption.

Stopping/reducing seed set

Alloftheherbicideandtillagetacticsdescribedsofar,whenappliedusingbestmanagementprinciples,shouldprovidegoodcontrolofFTRandsignificantlyreduceseedproduction.Mostweedcontroltacticsrarelyachieve100%control,soescapesorsurvivorswillbepresent.Fordifficult-to-controlweedsthatperpetuatethroughtheseed,itbecomescriticaltostopseedsetinthesesurvivors;otherwisetheproblemwillcontinue.Post-treatmentmonitoringofallweedmanagementpracticesisparamounttothesuccessofanyIWMplanasitallowsforthedetectionofsurvivors.Theseshouldthenbere-treatedbyspottillage,spotsprayingincludingweedsensorspraytechnology,ormanualremovalassoonaspossibletostopanyfurtherseedset.


Growingcompetitivecropswillalsoassistinreducingseedproduction.Usingmanipulativeagronomytomaximisecropcompetitionallowsthecropitselftobecomeanadjunctweedmanagementtool.Thisinvolves:

• selectingthemostcompetitivecrop(traditionally,barleyismorecompetitivethanwheat,maizeismorecompetitivethansorghum)

• selectingthemostcompetitivecultivars• sowingintoacleanseedbedtogivethe

competitiveadvantagetothecrop• aimingtoestablishthehighestcroppopulation

accordingtothecultivarandregion• keepingrowspacingstotheminimumforthe

cultivarandregion• ensuringgoodcropnutritionandcropprotection

practices(insectanddiseasecontrol).

Ifyouareunabletotakeadvantageofcropcompetitionandcropsarebeinggrownonwiderows,itbecomesveryimportanttousein-cropFTRmanagementpractices(seeFigure16).Takeadvantageofthewide-rowspacingtoutiliseinter-rowtillageorshieldedspraying(summercereals).Thewideinter-rowspacealsofacilitateseasierandgreaterherbicidepenetrationbelowthecropcanopy,whichisidealfortheGroupAgrass-selectivesappliedinbroad-leavedcrops.

Pre-harvestdesiccantsprayscanalsobeutilised(whereregistered)tocontributetothecontroloflatein-cropFTRemergencesorthesurvivorsofearliermanagementpractices.ObservationsmadeonlocalresearchtrialshavenotedthatapplicationsofGroup Mherbicide(whichisalsoacommon pre-harvestherbicide)causesFTRseedshedwithin2to3daysofspraying.Thisisparticularlyvaluableiftheseedbeingshedisnotphysiologicallymatureatthetime.

Figure 16. Dense infestation of FTR in a CQ wide-row wheat

crop that has not received any in-crop grass management

Preventing new seeds entering from outside

FTRplantsgrowingalongfarmtracksandpaddockverges,onfencelinesandaroundshedsandbuildingsareaseedsourcefornearbypaddockssincetheseedcanbedispersedshortdistancesbywind,andcarriedonanimalfurandonvehiclesandfarmequipmentthatpassthroughtheareas.Ideally,theseareasshouldbekeptFTR-freebutnotbaresinceFTR(andfleabane)areamongthefirstplantstocolonisebareareas.Sturdy,non-invasive,low-growinggroundcoversshouldbeencouragedintheseareas.

12

More information

Forfurtherinformationcontact:

Michael WidderickCropandFoodScience,Agri-ScienceQueensland Toowoomba,Queensland

Phone:(07)46398888 [email protected]

Tony CookTamworthAgriculturalInstitute NSWDPI

Phone:(02)67631250 [email protected]

YourlocalGrowerSolutionsteam:

Northern Grower AlliancePhone:(07)46395344 [email protected]

Central QueenslandPhone:(07)49837400 [email protected]

PreparedbyVikkiOstenwithinputfromMichaelWidderick(DepartmentofAgriculture,FisheriesandForestry),TonyCook(NSWDPI),StevenWalker(TheUniversityofQueensland),LawriePrice(NorthernGrowerAlliance)andGrahamSpackman(CentralQueenslandGrowerSolutions).

northern iwm fact sheet - department of agriculture and ... iwm fact sheet ... prolonged use and...

Documents