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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
Feathertop Rhodes grass: a weed best management guide 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)
Feathertop Rhodes grass: a weed best management guide5
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.
Feathertop Rhodes grass: a weed best management guide 6
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.
Feathertop Rhodes grass: a weed best management guide7
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
GroupDdinitroanaline 75
GroupKchloroacetamide 100
Sunflowers
GroupD(1)dinitroanaline 100
GroupKchloroacetamide 100
GroupD(2)dinitroanaline 100
GroupCtriazine 100
Mungbeans
GroupDdinitroanaline 100
GroupB(1)imidazolinone 100
GroupB(2)imidazolinone 100
noresidualonlypost-emergenceknockdowns 100
Fallow
double-knock:GroupMfollowedby GroupL+GroupBimidazolinone 100
3sequentialdouble-knocks(GroupMfollowedbyGroupL)withoutresiduals 100
Feathertop Rhodes grass: a weed best management guide 8
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
Feathertop Rhodes grass: a weed best management guide9
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
Feathertop Rhodes grass: a weed best management guide 10
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.
Feathertop Rhodes grass: a weed best management guide11
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).