Container Nursery Weed Control

http://edis.ifas.ufl.edu/ ( Publisher's URL )
MISSING IMAGE

Material Information

Title:
Container Nursery Weed Control
Physical Description:
Fact sheet
Creator:
Norcini, J. G.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
Publication Date:

Notes

Acquisition:
Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status:
Published
General Note:
"First published: January 1992. Revised: January 1994, August 1994."
General Note:
"Circular 678"

Record Information

Source Institution:
University of Florida Institutional Repository
Holding Location:
University of Florida
Rights Management:
All rights reserved by the submitter.
System ID:
IR00004608:00001


This item is only available as the following downloads:


Full Text

PAGE 1

Circular678 ContainerNurseryWeedControl1 J.G.NorciniandR.H.Stamps2Weedcontrolincontainer-grownornamental cropsisoneofthemostimportantculturalconcerns. Weedsareplantsgrowingwheretheyarenotwanted. Aplantcanbeaweedinonesituation,anda desirableplantinothersituations.Weedscompete withcropplantsforspace,water,lightandnutrients. Forexample,onecrabgrassplantinaone-gallon containercanreducethegrowthofan Ilexcrenata `Convexa'linerby60percent.However,evenif weedsdidnotreducegrowth,acontainerplantwith weedsisalessmarketableproductthanaweed-free product.Weedscanalsoharborinsectsanddiseases. Althoughthepredominantweedspecieschange fromseasontoseasoninFlorida,theamountof pressurefromthesepestplantsremainsconsistently high.Thispublicationprovidesinformationrelative toweedcontrolprinciples,commonweedplants, integratedweedcontrolprograms,andherbicide characteristics,availabilityanduse.COMMONWEEDSINFLORIDANURSERIESWeedscanbecategorizedasbroadleaves,grasses orsedges.Theymaybefurtherdistinguishedbythe lengthoftheirlifecycle.BroadleafWeedsBroadleafweedsareahighlyvariablegroupof plantsbutmosthavenet-likeveinsintheirleavesand manyhaveshowyflowers.Theyareeasytoseparate fromgrassesduetotheirgenerallydifferentleaf structureandhabitsofgrowth.Someexamplesof broadleafweedsareburningnettle,cocklebur, commonchickweed,creepingbeggarweed,creeping charlie,cudweed,eclipta,Floridapusleyorpurslane, Floridabeggarweed,henbit,pennywortordollarweed, andspurges.GrassWeedsTruegrasseshavehollow,roundedstems,and nodes(joints)thatareclosedandhard.Theleaf bladeshaveparallelveins,aremuchlongerthanthey arewide,andalternateoneachsideofthestem. Someexamplesaregoosegrass,crabgrass, crowfootgrass,sandbur,annualbluegrass, torpedograssandvaseygrass. 1.ThisdocumentisCircular678,FloridaCooperativeExtensionService,InstituteofFoodandAgriculturalSciences,UniversityofFlorida.First published:January1992.Revised:January1994,August1994. 2.JeffreyG.Norcini,associateprofessor,EnvironmentalHorticulture,NFREC-Monticello,FL32344;RobertH.Stamps,professor, EnvironmentalHorticulture,CFREC-Apopka,FL32703;CooperativeExtensionService,InstituteofFoodandAgriculturalSciences,University ofFlorida,GainesvilleFL32611. Theuseoftradenamesinthispublicationissolelyforthepurposeofprovidingspecificinformation.Itisnotaguaranteeorwarrantyofthe productsnamed,anddoesnotsignifythattheyareapprovedtotheexclusionofothersofsuitablecomposition. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

PAGE 2

ContainerNurseryWeedControl Page2SedgesSedgesareanimportantgroupof`grass-like' weeds;however,theyarenottruegrassesandare characterizedbyasolid,triangular-shapedstemwith leavesextendinginthreedirections.Thereare annualsedges(oftencalledwatergrasses),andthe predominantanddifficult-to-controlperennialsedges. Ofthelattergroup,yellownutsedgehasayellowish greenseedheadandreproducesbyseed,rhizomesand tubers.Therhizomesradiatefromtheplantwitha singlebulbortuber,theendofwhichmayproduce newplants.Purplenutsedgeisusuallysmallerthan yellownutsedge,hasreddishpurpleseedheads,and producesaseriesofbulbsonradiatingrhizomes called`tuberchains.' Theclassificationofweedsbasedonthelengthof theirlifecyclemaynotbeobviousonvisual inspectionbutwillhaveagreatimpactonthe selectionand/orsuccessofcontrolprocedures.The lifecyclecharacteristicsshouldbecomeanautomatic associationasspecificweedsandweedtypesare learned.Thethreebasiclifecyclesofweedplantsare annual,biennial,andperennial.AnnualWeedsAnnualweeds,asthenameimplies,complete theirlifecyclewithinoneyear.Theygerminatefrom seed,grow,flower,produceseedanddiein12 monthsorless.Thereareannualgrasses,sedgesand broadleafweeds.Inaddition,annualsmaybefurther categorizedas(a)winterorcoolseasonannuals,and (b)summerorwarmseasonannuals,basedonwhen theweedsgerminateandflourish.Weedssuchas crabgrassandspottedspurgearetypicalofsummer annuals.Theseweedssproutinthespringandthrive inthesummerandearlyfall.Henbit,common chickweed,andannualbluegrassaretypicalwinter annuals.Coolseasonweedslikethesesproutinthe fallandthriveduringthewinterandearlyspring.BiennialWeedsComparedtoannualweeds,biennialweedsare fewinnumber.Theseweedshavea2-yearlifecycle. Theygerminatefromseedinthefallanddevelop largerootsystemsandacompactclusterofleaves duringthefirstyear.Inthesecondyeartheyflower, produceseed,anddie.Examplesofbiennialweeds areCarolinafalsedandelion,wildcarrot,bullthistle, andsomecudweedspecies.PerennialWeedsWeedsthatlivemorethan2yearsareperennials. Theyreproducebyvegetativepartssuchastubers, bulbs,rhizomes(undergroundstems)orstolons (above-groundstems).Inaddition,many(likelongstalkedphyllanthus)alsoproduceseed.Duringthe winterseasonmostaredormantandmanylosetheir above-groundfoliageandstems.Inthespringthey initiategrowthfromfoodreservesintheirroot systems.Torpedograss,nutsedge,andvariousvines aremembersofthisgroupofweeds.Floridabetony isaperennialweedthat,underasubtropicalclimate, initiatesitsgrowthinthefall,growsduringthewinter monthsandgoesdormantduringtheheatofthe summer. Perennialweedsmaybefurtherdividedinto groupsbasedonthetypeofrootsystemand reproductiveprocess. Simpleperennials reproducebyseedsbutroot piecesdistributedbycultivationorother mechanicalmeanswillproducenewplants. Floridabetonyandsometreesandshrubsare characteristicofthisgroup. Bulbousperennials reproducebyseedandaboveorbelow-groundbulbs.Yellownutsedgeandwild onionshavetheirbulbsbelowgroundwhilewild garlichasanabove-groundbulb. Creepingperennials whichproduceseedbutalso producerhizomesorstolons.Bermudagrass, torpedograss,andpurplenutsedgeproducethese specializedstems(rhizomesandstolons)thatact asfoodstorageorgansandcaninitiategrowthat eachnode(joint)alongthestem. Perennialweedsarethemostdifficulttocontrol becauseoftheirgreatreproductivepotentialand persistence. Properidentificationoftargetweedsisnecessary beforeeffectivecontrolmeasurescanbeselected. Moreinformationregardingidentificationofweeds canbeobtainedfromcountyExtensionoffices.WEEDCONTROLPRINCIPLESSeedcanbedistributedbypeople,animals,birds, windand/orwater,andarethemostimportantweed sourceinFloridanurseries.Weedrootpiecesmust

PAGE 3

ContainerNurseryWeedControl Page3bemovedmechanicallytothecontainerby contaminatedmedia,containersorliners. Preventativeweedcontrolistheobjectiveofany programbecausecontrolofestablishedweedsin containersislimitedprimarilytohandlabor. Effectivepreventionrequiresproperemphasisbe placedonnurserysanitation.Sinceseedsarethe mainweedsource,reductioninweedseednumberin theproductionareashouldbeahighpriority. Althoughsomeweedseedsarewind-blownforseveral miles,mostonlymoveashortdistance.Thus, eliminationofseed-bearingweedsadjacentto productionareaswillreducetheweedseed population.Weedsthatdodevelopincontainers shouldnotbeallowedtoflowerandsetseedbefore theyareremoved.Weedseedcanalsobedistributed tocontainersthroughirrigationwater,especiallyifa surfacewatersourceisused.Eliminationofseed producingweedsnearsurfacewaterscanreducethis problem.Irrigationsystemfilterscanremovemany weedseedsbeforetheyreachthecontainers. Containermediamaycontainweedseedorvegetative propagules.Contaminationcanoccurbeforemedia componentsarepreparedandduringmixingor storage.Nativepeatmaycontainviableseedor propaguleseventhoughitwasdugfrombogs20or30 feetdeep.Mediashouldnotbepreparedorstoredin areaswithhighweedpopulations. Rootedcuttingsandseedlingstransplantedfrom propagationbedsorcontainerscantransferweed problemsfromthepropagationareatoproduction areas.Therefore,itisessentialthatpreventative weedcontrolstartwiththepropagationphaseof production.Iflinersorseedlingsarepurchased,care mustbetakentoensurethatonlyhighqualityweedfreeplantsarebroughtintotheproductionsystem. Ithasbeenestimatedthatcontrollingweedswith onlyhandlaborwouldcostinexcessof$6000per acreperyear.Thiscouldaccountforupto30 percentoftotalproductioncosts,withoutconsidering growthreductionduetoweedcompetitionbetween weedings.Althoughsomehandremovalofescape weedsmaybenecessary,preventativeweedcontrol withherbicidesmayaccountforaslittleas3percent ofthetotalproductioncosts.Weedcontrolfor containernurseriesmuststartwithcleanproduction areasthatarekeptcleanthroughanintegrated preventativeprogram.WEEDCONTROLMETHODSWeedcontrolcanbeaccomplishedbyphysicalor chemicalmeansorbyacombinationofthetwo. Mechanicalweedcontrolcanconsistofcultivationor mowingofsurroundingareas,useofgroundcoverson productionbedsandhandweeding.Chemicalweed controlconsistsofpreemergenceandpostemergence herbicides.PhysicalControlsWeedsinnonproductionareascanbecontrolled bycultivation,chemicalsorcompetitionfrom groundcovers,suchasturfgrass.Cultivationis expensiveandpredisposesthesoiltoerosionbywind andwater.Cultivationwithinthecontainer productionareasisimpractical.Turfgrassesaretough competitorsforweedsifproper,yetlowmaintenance schedulesarefollowed.Turfgrassselectionshouldbe basedonseedproductioncharacteristics,toleranceof traffic,andnutrition,lightandirrigation requirements. Mulchesincontainerproductionareasareusedto stabilizeproductionbedsurfacesandpreventweed growth.Blackplasticisbyfarthemostcommon groundcover.Althoughsomeweedscanpenetrate theplastic,mostwillnot.Careshouldbetakento minimizethenumberandsizeofholesmadeinthe plasticsinceeachholerepresentsasiteforweed establishment.Chemicalpretreatmentunderthe plastichasproventobehelpfulandwillbediscussed inmoredetailinthenextsection.Somewoven plasticfabricsprovideabarriertoweedgrowthby reducinglightbutallowwaterpenetration.Plastic materialswilllastfrom1to4yearsinfullsun productionareasbutultravioletlightinhibitorsare requiredforplasticgroundcoverstolastmorethan oneyear.Someplasticgroundcoversmaylastfor morethan8yearsinshadedproductionareas. Gravelplacedoverblackplasticfilmmaybeused,but itisexpensiveandprovidesaplacewhereweedseeds cangerminateandbecomeestablished.Organic groundcoversormulchessuchaspinebark,sawdust orcypressshavingsbreakdownrapidly,providea goodenvironmentforweedseedgerminationand maybe movedeasilybywindandwater. Organicmulchescanalsobeplacedonthe surfaceofcontainermediatoprovideshortterm weedcontrol.Inorganicmulches,suchasplasticand fiberglassdiscs,havebeenevaluatedbyresearchers,

PAGE 4

ContainerNurseryWeedControl Page4butduetoeconomicconsiderationsandreductionin airexchangewiththemedia,theuseofsuchmulches hasbeenlimited.ChemicalControlsChemicalweedcontrolwithherbicideshas reducedgreatlythecostofweedcontrolinFlorida nurseries.Annualherbicidecostsmaybeone-tenth thatofhandlaborforweeding.Herbicidesarea groupofchemicalcompoundsthatcontrolplant growthanddevelopmentbyinterruptingsome metabolicpathwayorbycontactaction.Plant responsetothesechemicalsdependslargelyon concentrationofthechemicalapplied.Forexample, 2,4Dcaneffectivelycontrolbroadleafweedsbutat lowerconcentrationsthischemicalexhibitsgrowthregulatingpropertiesbystimulatingrootingofcuttings incertaincases. Herbicidesmaybeselectiveornonselective throughchemicalcharacteristicsorrateadjustment. Selectiveherbicides killsomeplantswithlittleorno effectonotherplants. Nonselectiveherbicides are toxictomostplants.Herbicidescreeningresearch identifiestheselectiveraterangeofthesechemicals tofindcompoundsthatarenottoxictocropplants butthatcontrolmanyweedplants. Someherbicideswillkillonlytheplanttissuewith whichtheycomeincontact,whileothersareabsorbed bytheplantandtransportedwithintheplanttoother plantparts.Contactherbicidesmaykillthefoliageof perennialplantsbutregrowthfromtherootsislikely. Translocatedorsystemicherbicidesmayaffectthe entireplant. Preemergenceherbicides preventseedling emergenceanddevelopmentandareappliedtothe surfaceofweed-freecontainermediaandsurrounding productionareaswhenthecropfoliageisdry.Most preemergentherbicidesrequireoverheadirrigationto activatetheherbicideand/orincorporateitintothe growingmedia.Incontainers,thisisaccomplishedby applyingtto2inchesofwater.Theamountof irrigation,aswellastheamountoftimebeforethe herbicidemustbeincorporated,varieswitheach herbicidesocheckthelabelforthisinformation. Postemergenceherbicides areappliedtoexisting weeds.Theyaremosteffectivewhentheweedsare smallandactivelygrowing.Theseherbicidesmust remainonweedfoliageoneormorehourstobe effective.Checktheproductlabelsincethetime varieswiththeherbicide.Mostpostemergent herbicideslabeledforuseincontainercropsarefor controlofgrassweeds.Thesegrass-controlherbicides canbeappliedover-the-toptobroadleafornamentals. Innoncropareasaroundthebedsnonselective herbicidessuchasRounduporDiquatcanbeusedto controlweeds. Herbicidesareformulatedaswettablepowders (WorWP),dryflowables(DF),waterdispersible granules(WDG),solutions(LorS),granular(G)or emulsifiableconcentrates(EorEC).Ifgiventhe choice,selectDForWDGformulationsoverWP formulationsbecauseDFsandWDGsaresaferfor theapplicatorduetothereduceddustassociatedwith theseformulations.Granularherbicidesareapplied drytocropareas.Allotherformulationsaremixed withwaterandappliedusingasprayer,orinsome casestheirrigationsystem.Goodagitationinthe spraytankisnecessarytoprovideuniformapplication rates.Theamountofactiveingredientinaherbicide formulationispresentedasanumberinfrontofthe formulationdesignation(G,W,WP,DF,WDG,E, EC,L,S)onthelabel.Forexample,a4percent granularherbicidewouldbeidentifiedasa4G material,with4poundsofactiveingredientin100 poundsofproduct.A75percentwettablepowder(or dryflowableorwaterdispersiblegranule)islabeled as75WP(or75DFor75WDG),whichmeansthat3 ofevery4poundsofmaterialinthebagisactive ingredient.Liquidformulationsarelabeledaspounds ofactiveingredientpergallonofproduct.For example,a2ECcontains2poundsofactive ingredientpergallonofproduct. Selectionofaherbicideshouldbebasedonthe weedstobecontrolled,theexistingweedpopulation, lengthofcontroldesiredandspecificcropplants involved.Thefollowingherbicidedescriptionsshould behelpfulinchoosingthepropermaterialforaweed controlprogram.Alwaysfollowthelabelinstructions andrestrictions.Thefollowingdescriptionsarenot recommendations,butareintendedasbackground information.Thechemicalnameislistedfirst, followedbytradename(s)inparentheses.Trade nameslisteddonotimplyanendorsementofthat particularproduct.PreemergenceHerbicidesBenefinplusoryzalin (XL) availableonlyasa2G, istheherbicidetousewhenyouwantagranularform oforyzalin(Surflan).Thetwoactiveingredientsare ina1:1ratio.Itwillcontrolmostannualgrasses

PAGE 5

ContainerNurseryWeedControl Page5(includingcrabgrasses,foxtails,andgoosegrass)as wellascommonchickweedandhenbit.Itissafeto useonabroadspectrumofornamentals DCPA (Dacthal) isavailableonlyasa75W.It willcontrolsomeannualgrassesandbroadleaves includingcrabgrass,foxtails,commonchickweed,and Floridapusley. Dichlobenil (Casoron,Dyclomec,Norosac) canbe usedasapretreatmenttocontainerproductionbeds beforeputtingdownblackplasticorotherphysical barriers.Applicationsof4to6poundsofactive ingredientperacrefromthe10Gformulationofthis herbicideareappropriateforthispurpose.Itshould notbeusedincontainersbecauseofitsvolatilityand leachability. Isoxaben (Gallery) isavailableasa75DF.Itis usedforcontrolofmanybroadleafweedsincluding woodsorrel,spurges,bittercress,commonandmouseearchickweed,andpennywortordollarweed.Itis safetouseonawidevarietyofornamentals. Isoxabenplusoryzalin (SnapshotDF) contains 80%activeingredients,with60%oryzalin(Surflan) and20%isoxaben(Gallery).Thecombinationof ingredientsprovidesexcellentcontrolofmostweeds foundincontainernurseries,includingcommon chickweed,spurges,woodsorrel,andannualgrasses. Itissafetouseonawidevarietyofornamentals,and isagoodchoiceforspurgeorchickweedcontrol. Isoxabenplustrifluralin (SnapshotTG) isa2.5G formulationthatcombines0.5%isoxaben(Gallery) with2%trifluralin(Treflan).Thiscombination controlsorsuppressesafairlybroadrangeofgrasses andbroadleavesincludingcommonchickweed, spurges,woodsorrel,andannualgrasses. Metolachlor (Pennant) isavailableasa7.8ECand 5G.Itisprimarilyusedforpreemergentcontrolof yellownutsedge,althoughitwillalsoprovidesome controlofannualgrasses(includingcrabgrassand foxtail)andbroadleafweeds(includingpigweed, Floridapusley,andcarpetweed).Itissafeonawide varietyofornamentals.Donotapplyitmorethan twotimesperyear. Metolachlorplussimazine (Derby) isa5G formulationcontainingbothPennant(metolachlor) andPrincep(simazine)ina4:1ratio.This combinationallowscontrolofcommonchickweed, spottedspurge,annualgrasses,andyellownutsedge. Itisprimarilyforuseonwoodyornamentals.Donot makemorethantwoapplicationsperyear. Napropamide (Devrinol,Hurdle,Ornamental Herbicide5G) isavailablein2G,5G,and50WP formulations.Itislabeledforuseonawiderangeof container-grownornamentals.Itiseffectivefor controlofgrassesbutlesseffectiveonspurgesand certainbroadleafweeds.Applicationof4to6 poundsofactiveingredientperacreshouldbe repeatedevery8to10weeks. Oryzalin (Surflan) isavailableasaliquid(4S), andwillpreventemergenceofmostannualgrasses andmanybroadleafweeds(includingcommon chickweed,Floridapusley,andpigweeds).Long-term useofthisherbicideonthesamecropisnot recommendedbecauseofpossiblerootinhibition. Thisnonvolatileherbicidecanbeappliedinany season. Oxadiazon (Ronstar) isavailableasa2Gor 50WP,andislabeledforawiderangeofcontainergrownornamentals.Itcontrolsmostnurseryweeds, buthaslimitedeffectonspurgesandchickweed.It shouldnotbebroadcastonplantswithrosettes(such asdaylilyorliriope),whorlsorwetfoliage. Applicationsof2to4poundsofactiveingredientper acrecanberepeatedevery8to16weeks. Oxyfluorfenplusoryzalin (Rout) isa3G formulation.Theactiveingredientsareoxyfluorfen (Goal)andoryzalin(Surflan)ina2:1ratio.Routis registeredonawidevarietyofornamentalsandgives preemergencecontrolofabroadspectrumofweeds includingspurges.Apply3poundsofactive ingredientperacreevery3monthsduringthe growingseason.AvoiduseofRouton`Hino-crimson' and`Snow'azaleas,andcrapemyrtles. Oxyfluorfenplusoxadiazon (OO-Herbicide) isa3G formulationcontainingoxyfluorfen(Goal)and oxadiazon(Ronstar)ina2:1ratio.Thiscombination canprovidecontrolofabroadspectrumofweedson awiderangeofcrops.Itshouldnotbebroadcaston wetfoliageorplantswithrosettesorwhorls.Itmay beappliedat3to4monthintervalsatarateof3 poundsofactiveingredientperacre. Oxyfluorfenpluspendimethalin (Ornamental HerbicideII) isalsoa3Gformulation.Thetwo activeingredients,oxyfluorfen(Goal)and pendimethalin(Pendulum,SouthernWeedgrass Control)ina2:1ratio,allowthisproducttocontrol

PAGE 6

ContainerNurseryWeedControl Page6awiderangeofnurseryweeds,andespeciallyspurges. Applicationsof3poundsofcombinedactive ingredientperacrecanberepeatedevery10to12 weeks.AswithRonstar,avoidbroadcastapplication toplantswithrosettes,whorlsorwetfoliageasinjury mayoccur.Severalazaleacultivarsarealso susceptibletoinjury. Pendimethalin (Pendulum,SouthernWeedgrass Control) isformulatedasa2.68G(SWC)anda 60WDG(Pendulum).Itprovidescontrolofsome annualgrasses(includingcrabgrass,foxtail,and goosegrass)andbroadleafweeds(includingprostrate spurge,commonchickweed,andwoodsorrel).Itis labeledforuseonabroadspectrumofornamentals. Prodiamine (Factor) isa65WGformulationand islabeledforafairlywiderangeofcontainer-grown ornamentals.Itcontrolsabroadspectrumofweeds includingspurges.Donotapplymorethan1.5 poundsofactiveingredientperacreperyear. Simazine (Princep,Simazine,Sim-Trol) is availableasa4G,4L,80W,and90WDG.Itcontrols severalannualgrasses(includingcrabgrassand foxtails)andbroadleafweeds(includingcommon chickweed,Floridapusley,andpigweed).Itissafeto useonjunipersandseveralotherwoodyplants,but donotapplyitwithinoneyearaftertransplanting.It isappliedinfallorspring,butonlyonceperyear exceptasdirectedforquackgrasscontrol. Trifluralin (Treflan) ismarketedas4ECand5G formulations.Thisvolatileherbicidecontrolsmost annualgrassesandmanybroadleafweedsat1to4 poundsofactiveingredientperacreandshouldbe irrigatedimmediatelyafterapplication.Trifluralin inhibitsrootgrowth,butremainswhereitisapplied withminimalleaching.PostemergenceHerbicidesBentazon (Basagran,Lescogran) isavailableasa 4EC.Itisacontactherbicidethatisrecommended forcontrolofyellownutsedgeandsomebroadleaf weedsinliriopeandEnglishivyonly.Inthesecrops, itcanbeappliedasanover-the-topspray.Youmay noticeminorchlorosisof`EvergreenGiant'liriope onetotwoweeksafterapplication.Twoapplications 7-10daysapartarerequiredforyellownutsedge control.Acropoilshouldbeaddedtothesprayfor controlofyellownutsedge.Basagranwillonlykillthe above-groundportionofweeds.Alloweighthours afterapplicationbeforeoverheadirrigationfor maximumactivity. Diquat (DiquatHerbicideH/A,Reward) isa2S formulationthatkillsallplantfoliageoncontactand hasnoresidualactivityinsoil.Effectsshouldbe noticedwithintwotothreedays.Thematerialisnot translocatedandregrowthofperennialweedsislikely. Diquatisappliedasadirectedspray;contactwith greenbarkorsuckersofsomeornamentalplantswill causeinjury.Anozzleshieldwillimproveselective placement.Inclusionofanonionicsurfactantinthe sprayisrecommended.Extremeprecautionshouldbe takentopreventskincontact,inhalationofspraymist, soakingofabsorbentclothingoreyecontact. Fluazifop (Ornamec,Take-Away) sethoxydim (Vantage) and fenoxyprop (Acclaim) areall postemergencegrassherbicidesregisteredforoverthe-topcontrolofmanyannualand/orperennial grasses.UseanonionicsurfactantwithAcclaimand Ornamec.NosurfactantisnecessarywithVantage (replacedPoaststartingJanuary,1992)asitisalready includedintheproduct.Whilemostbroadleafplants aretolerant,directedspraysmustbeusedwithcertain species.Donotapplyanyoftheseproductsifrainis expectedwithinanhourafterapplication.No preemergencesoilactivityisexpected. Glufosinate-ammonium (Finale) isanonselective contactherbicidewithsomesystemicaction.THis water-solubleliquidherbicidecontains1poundof activeingredientpergallonandisappliedonasprayto-wetbasis(priortorunoff)ongreentissueof undesirablevegetation.Checklabelforrates dependingonsizeandspeciesofweedtobe controlled. Glyphosate (ExpediteGrassandWeed,Roundup) are4Sformulationsofanonselectivetranslocated, postemergenceherbicide.ForRoundup,ratesof1to 4poundsofactiveingredientperacrein20to50 gallonsofwaterwillkillmostactivelygrowingplants. AlthoughExpediteGrassandWeedismore expensive,itcomespremixed.Glyphosateisabsorbed bygreenfoliage,stemsandbranchesandtranslocated throughouttheplants.Sixhourswithoutrainisthe recommendedtermformaximumabsorption. Glyphosaterequires3to10daysormoretokillmost plantsandarepeatapplicationmayberequiredfor plantswithextensiveundergroundstorageorganslike nutsedgeandbermudagrass.Glyphosateisrapidly deactivatedinmostsoils;therefore,adirectedspray

PAGE 7

ContainerNurseryWeedControl Page7aroundcropplantsiseffectiveandreplantdelaysare notnecessary. Oxyfluorfen (Goal),availableasa1.6E,provides earlypostemergence(weedsupto4inchestall)of severalannualgrasses(includingcrabgrass, goosegrass,andfoxtail)andbroadleafweeds (includinglambsquarters,pigweeds,henbit,and woodsorrel).Italsogivespreemergencecontrolof thosesamegrassesandbroadleafweeds,aswellas manybroadleafweedssuchasspottedandprostrate spurge.Goalisforuseinconifersonly,primarily junipersandarborvitae.Checkthelabelforspecific species. Paraquat (Gramoxone) actsthesameasdiquat, buteffectswillprobablybenotedsoonerthanwith diquat.Inclusionofasurfactantinthesprayis recommended;however,donotuseananioniccrop oilconcentrateorsurfactantasaninsoluble precipitatemayform.Gramoxoneisarestricteduse pesticideinFloridaandextremeprecautionshouldbe takentopreventskincontact,inhalationofspraymist, soakingofabsorbentclothingoreyecontact. Pelargonicandrelatedfattyacids (Scythe) isa nonselective,strictlycontactherbicidewhoseeffects canbeobservedwithinhoursofapplicaiton.Spray solutionconcentrationsrangefrom5to10%andwill killtheabove-groundfoliageandothernonwoody tissueofotherplants.EnvironmentalEffectsEnvironmentalconditionscanchangetheactivity ofherbicidesoralterplantresponsetothese chemicals.Thesmallvolumetosurfaceareaof containersexposesthemediumandrootsystemof container-grownplantstowidetemperature variations.Containerplantsgrownoutdoorsmay receiveupto160inchesofwaterannuallyand excessiveirrigationmayresultinherbicideleaching. Effectivepreemergenceherbicidesincontainers mustremaininthetopsurfaceofthemediumand notmoveintotherootzone.Manyofthese herbicideswillinhibitrootgrowthifleachingoccurs. Mediacontainingapproximately50%byvolumepine barkseemtoholdherbicidesinthesurfacelayer moreeffectivelythanpeatandsandmedia components. Wettingagentsareappliedtocontainermediato facilitatethoroughwettingofpeatandpinebark particles.Sincethesematerialsdecreasethesurface tensionofwaterandallowmorerapidwater dispersion,theireffectsonherbicideleachingthrough thedepthsofcontainermediahavebeenquestioned. However,inapreliminarystudythreewettingagents didnotincreaseleachingoftrifluralin(Treflan)or oxadiazon(Ronstar)appliedatrecommendedrates. Enclosedstructuressuchasgreenhousespose seriouslimitationsforherbicideuse.Onemustbe concernednotonlywithphytotoxicityfromdirect contactfromchemicalsbutalsowiththevolatilityof thechemicalsinapartiallyclosedsystem.Onlyfour herbicidesarelabeledforuseingreenhouses: glyphosate (Roundup), diquat (DiquatHerbicide H/A,Reward), oryzalin (SurflanA.S.).Besurethe fansareoffwhenapplyingherbicidesingreenhouses, andcheckthelabelforthere-entryinterval.HERBICIDEAPPLICATIONHerbicidesareusuallyappliedinliquidor granularformulations.Mostlabeledpreemergence herbicidesforcontainerproductionaregranular formulationstoensureapplicationtothemedium surfacewithlimitedfoliarcontactanddrift.Itis essentialthatallpreemergenceherbicidesbeapplied evenlyoverthetargetarea.Mostpostemergence herbicidesareliquidformulationstofacilitate thoroughweedcoverage.Generalapplication proceduresandguidelinesforequipmentcalibration forgranularandliquidherbicideformulationsare presentedbelow.GranularHerbicideApplicationTheuseofgranularherbicidesintheproduction ofcontainerornamentalsrequiresaccurate application.Aproperlycalibratedrotaryordrop spreaderisessentialinachievinguniformcoverage, butmustbecalibratedforeachoperatorandeach granularherbicide.Aperiodicrecheckofthe calibrationisdesirablesincegranuleparticlesize, particledensity,humidity,humanvariabilityandwind canaffecttheaccuracyofapplication.Inpractical use,windvelocitiesofgreaterthan5mphseverely distorttheuniformityofmostapplicationsandswath width. Thefollowingisageneralcalibrationmethodfor granularapplicators.Wherespecificinstructionsare statedbythemanufacturerofeitherthegranular herbicidespreaderortheherbicide,followthose directions.Followthesesteps,inorder.

PAGE 8

ContainerNurseryWeedControl Page81.Markoutatestareaof200squarefeet. 2.Weighoutenoughherbicidesothattherewillbe someleftoverafterapplyingittotheteststrip; placeitintheapplicator. 3.Applytheherbicidetotheteststrip. 4.Weightheleft-overherbicideintheapplicator. 5.Calculatetheamountusedbysubtractingthe amountleftoverfromwhatyoustartedwith. 6.Determinetheapproximaterateperacreby multiplyingtheamountusedby220.Fortherate per1000ft2,multiplytheamountusedby5. 7.Adjusttheequipmentandrepeatthetestuntil thedesiredrateperacre(orper1000ft2)is achieved. Note: Thiscalibrationprocedureshouldbedone foreachspreader,spreadersetting,andindividual applyinggranularherbicidesduetovariationsin equipment,walkingspeeds,andotherfactors. Ahand-heldshakercanbeutilizedtoapply granularherbicidestoasmallnumberofcontainers ortoextremelylargecontainers.Thismethodmaybe usefulfortreatingfreshlypottedplantswhilestillon thetrailerbeforetheyarespacedintheproduction area.Thiscouldsavetimeandchemicalsandensure thatpreemergentherbicideapplicationsweremade beforeweedemergence.Aftertheamountofsurface areatobetreatedatonetimehasbeendetermined, therecommendedamountofherbicidecanbeplaced intheshakerandapplieduniformlytothearea. Safetyprecautionsshouldbefollowedrigidly.LiquidHerbicideApplicationApplicationofliquidformulationstolargeareas canbeaccomplishedwitheitheracontinuouspump backpacksprayerortractor-mountedsprayer. Regardlessofthetypeofsprayerusedtoapply herbicides,thespeed,pressureandnozzleheightmust bekeptconstantforaccurateapplication.The backpacksprayermayrequiresomemodificationso thatitisbettersuitedforherbicideapplication.A pressuregaugemountedonthetanksideofthe shutoffvalvewillallowcontinuousmonitoringofthe tankpressure,whichmustremainuniform.Optimum pressurecontrolcanbeachievedbyinsertinga pressureregulatorbetweenthepressuregaugeand nozzle.Topreventdrippingaftertheshutoffvalveis closed,useaquick,positivepressureshutoffvalveor astrainerwithacheckvalve.Nozzleclogging,a problemassociatedwiththeuseofwettablepowders (aswellasDFandWDGformulations)canbe reducedbyinsertinga50meshin-linestrainerand keepingtheherbicidesolutionconstantlyagitated. Listedbelowaregeneralcalibrationprocedures forcontinuouspumpbackpacksprayersandtractormountedsprayers.ContinuousPumpBackpackSprayer Calibration1.Ondrygroundorpavement,markoffanarea equaltothedesiredbandorbroadcastwidth. 2.Partiallyfillthesprayerwithwater.Pumpupthe sprayertothedesiredpressure. 3.Adjusttheheightofthenozzle(orboomifyou arebroadcastspraying)soastoachievethe desiredbandorbroadcastwidthwhilespraying forafewsecondsatatimeonthedryareas withinthemarkedarea.Besuretopumpwhile sprayingtomaintainauniformpressure. Nozzleheight= feet. Example: Band 4-ftbandwithnozzleheightat2 feet. Broadcast 7-ftspraywidthwithnozzleheight at3 feet. 4.Inanareawithaterraintypicalofthattobe sprayed,markoffadistanceof100feet. 5.Refillthesprayerwithwater.Whilepumpingand sprayingandwiththenozzleatthedesiredheight, recordthenumberofsecondsittakestowalkthe calibrationdistanceatasteady,comfortablepace. Timetowalkthecalibrationdistance= seconds. Example:Timetowalkthe100feetwas23 seconds. 6.Collectthesprayoutputfromonenozzleforthe samenumberofsecondsittooktotravelthe calibrationdistance.Foraboomsprayer,repeat thisstepforeachnozzle.Thencalculatethe averagenumberofouncescollectedpernozzle.

PAGE 9

ContainerNurseryWeedControl Page9Band:Collectedwater= ounces. Example:Collected35 oz.ofwaterfromthe nozzleover23seconds. Boom:Averagecollectedwater= ounces. Example:BroadcastCollected12 oz.fromthe 1stnozzle,14 oz.fromthesecond,and14 oz. fromthethirdnozzle.Theaveragenozzleoutput= (12+14+14)/3=13.3 oz. 7.Calculatethegallonsperacre(GPA)asshownin Equation1andEquation2: *SeeAppendixforhowthe constant3.4 is (1) (2) derived. 8.ToobtainadifferentGPA,changethepressure, walkingspeed,and/ornozzleorificesize,and repeatthestepsabove. 9.Determinetheamountofchemicaltoaddtothe tankbyfirstdeterminingthefractionofanacre thatcanbesprayedwithonetankful.(See Equation3.) Then,multiplytheapplicationrateoftheproduct (3) peracrebythefractionofanacrecoveredbyone tankfultoobtaintheamountofproductper tankfulofspray.(SeeEquation4.) Example:Amountofproducttoaddforone5(4) gallontankfulofspraydeliveredat29.8GPAthat wouldcover0.17acreswhentheherbicideshould beappliedatarateof4poundsproductperacre. (SeeEquation5.) (5)Tractor-MountedSprayer1.Inanareawithaterraintypicalofthattobe sprayed,markoffanarea330feetlongwithtwo stakes.Thesprayerwillbecalibratedoverone roundtrip,thatis,660feet. 2.Partiallyfillthespraytankwithwater. 3.Adjustthepressureregulatorsoastoachievethe desiredpressurewiththeengineRPMstobe usedduringspraying.Shutoffthesprayer.Note theRPMsandspraywidth. RPMs= Spraywidth= feet. Example:Spraywidth=20 feet. 4.Fillthespraytankwithwatertofullorsome measurablepoint. 5.Selectasafespeedtobeusedforspraying.Start thetractorabout30feetfromthefirststakewith thecut-offvalveclosed.Uponreachingthefirst stake,openthecut-offvalveandstartspraying. Notethegearthatisused.Uponreachingthe secondstake,turnoffthesprayerandturnthe tractoraround.Respraytheareawhile maintainingthesamepressureandspeedusedon thefirstpass. Gear=

PAGE 10

ContainerNurseryWeedControl Page106.Measuretheamountofwater(tothenearest quart)thatittakestorefillthetanktothe originallevelinStep4.Besuretorefillthetank inthesamespotasinStep4toavoiderrors. Thisistheamountofwaterusedoverthe660footcourse. Amountofwaterusedin660feet= Example:Amountofwaterusedin660feet= 15.25 gallons(thatis,15gallonsplus1quart). Calculatethegallonsperacreasshownin Equation6: *SeeAppendixforhowthe constant66 is (6) derived. 7.ToobtainadifferentGPA,changethepressure, tractorspeed,and/orthenozzleorificesize,and repeatthestepsabove. 8.Determinetheamountofchemicaltoaddtothe tankbyfirstdeterminingthefractionofanacre thatcanbesprayedwithonetankful.(See Equation7.) (7) Then,multiplytheapplicationrateoftheproduct peracrebythefractionofanacrecoveredbyone tankfultoobtaintheamountofproductper tankfulofspray.(SeeEquation8.) Example:Amountofproducttoaddforone50(8) gallontankfulofspraydeliveredat50.3GPAthat wouldcover1acrewhentheherbicideshouldbe appliedatarateof4poundsproductperacre. (SeeEquation9.) (9) Applicationofliquidherbicidestosmallareascan beaccomplishedwithacontinuouspump backpacksprayerorhand-heldcompressiontype sprayer.Calibrationprocedureslikethose describedabovearenotnecessaryinthiscase. Justaddtheamountofherbicideneededtotreat theareatoenoughwatertouniformlyspraythe areaatleasttwotimes.Youmaywanttoadda dyetothespraysolutionasanindicatorofspray coverage.Thedyeshouldbreakdowninthesun afterthreetofourdays.

PAGE 11

ContainerNurseryWeedControl Page11APPENDIX TheConstant3.4Thisistoshowthederivationoftheconstant3.4 usedinthevariousequations.(SeeEquation10.) Giventhatwewanttodeterminethesprayerdelivery (10) rateinGPA,andthatthereare128ouncespergallon and43,560squarefeetperacre,then: Theconstant3.4isderivedbydividingthe amountofwatercollectedfromthenozzlein gallons(thatis,thefractionofagallon)bythe area(inacres)coveredduringcalibration,thatis, thefractionofanacre.(Seeseriesofequations inEquationBox11.) (11)TheConstant66Thisistoshowthederiviationoftheconstant66 usedintheequation.(SeeEquation12.) Giventhatwewanttodeterminethesprayerdelivery (12) rateinGPA,andthatthereare128ouncespergallon and43,560squarefeetperacre,then: Theconstant66isderivedbydividingtheamount ofwater,ingallons(tothenearestquart),thatis usedtorefillthetankbythearea(inacres) coveredduringcalibration,thatis,fractionofan acre.(SeeseriesofequationsinEquation13.) (13)