Herbicide Calibration And Application

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Title:
Herbicide Calibration And Application
Physical Description:
Fact sheet
Creator:
Tucker, D.P.H.
Publisher:
University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication:
Gainesville, Fla.
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Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
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Published
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"Publication date: June 1994."
General Note:
"HS-184"

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University of Florida Institutional Repository
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University of Florida
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All rights reserved by the submitter.
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IR00004652:00001


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FactSheetHS-184 June1994HerbicideCalibrationandApplication1 D.P.H.TuckerandM.Singh2Improperapplicationofherbicidesaccountfor mostoftheunsatisfactoryresultsfromherbicide programsincitrus.Inadequateratesanduneven distributionwillresultinpoorweedcontrol,while excessiveratesandspraypatternoverlapmayresult inyoungtreeinjury.Ultimately,theneedfor reapplicationand/orexcessiveherbicideusagewill increasethecostoftheweedcontrolprogram. Adequatespraypatternoverlapiscriticalto uniformweedcontrol.Properboomheightabovethe surfacetobesprayedalongwithcorrectnozzle spacingareessentialforthedesireddegreeof overlap.Aseachnozzletypehasdifferentoverlap characteristics,determiningtherequirementsfor optimumoverlapwillensureevenherbicide distributionoverthetargetarea.EQUIPMENT PumpThepumpisthebigcomponentoftheherbicide applicatorandmusthavethecapacitytodeliver enoughspraymixtoproviderequiredboomdelivery rateandenoughreturnflowforproperagitationif hydraulicagitationisused.Thepumpmustbeableto functionatpressuresdesiredforthecorrectoperation ofnozzletypesselected.Operatingpressuresshould rangefrom20to40psi.Pumptypesusedincitrus weedcontroloperationsinclude: Rollerpumpswhichdelivermediumvolumesat lowtomediumpressure.Theabrasiveactionof wettablepowderswillresultinwearoftheir internalparts. Pistonpumpswhichdeliverlowtomedium volumesathighpressures.Asurgetankisneeded toreducepressuresurgescausedbypistonspeed variation. Centrifugalpumpswhichdeliverhighvolumesat relativelylowpressures.AgitationAllherbicideproducts,particularlywettable powders,waterdispersiblegranules,andflowable formulationsrequireagitationtoachieveinitial thoroughmixing.Mechanicalagitationisbest,but hydraulicagitationmaybeusedprovidedanadequate amountofturbulentflowenergyfromacombination ofpressureandvolumeistransportedbacktothe bottomofthetank.Improperagitationwillcausean accumulationofproductatthebottomofthetank withtheresultingunevenherbicideconcentration throughoutthevolumeofcarrierinthetank.Thiscan leadtoexcessiveapplicationratesearlyinthe operationandinadequateratesattheend.Possible endresultsincludephytotoxicitysymptomsintrees andpoorweedcontrol,respectively. 1.ThisdocumentisFactSheetHS-184,aseriesoftheDepartmentofHorticulturalSciences,FloridaCooperativeExtensionService,Institute ofFoodandAgriculturalSciences,UniversityofFlorida.Publicationdate:June1994. 2.D.P.H.Tucker,professor,horticulturist,DepartmentofHorticulturalSciences;M.Sing,professor,weedscientist,DepartmentofHorticultural Sciences,CitrusResearchandEducationCenter,LakeAlfred,Florida,abranchcampusoftheUniversityofFlorida,Gainesville,Florida. Theuseoftradenamesinthispublicationissolelyforthepurposeofprovidingspecificinformation.Itisnotaguaranteeorwarrantyofthe productsnamed,anddoesnotsignifythattheyareapprovedtotheexclusionofothersofsuitablecomposition. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

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HerbicideCalibrationandApplication Page2StrainersandScreensStrainersandscreensareessentialcomponentsof herbicideapplicationequipmenttoavoidpluggingof nozzletipsandpossibledamagetopumps,pressure regulators,andgauges.In-linestrainersshouldbe situatedonthesuctionlinebetweenthetankand pumpwhererollerandpistonpumpsareused,and betweenthepumpandpressureregulatorfor centrifugalpumps. Nozzlescreensshouldbeplacedineachnozzle housingandequippedwithcheckvalvestominimize dripwhentheboomisnotinoperation.RegulatorsandGaugesRegulatorsandgaugesareessentialcomponents ofallherbicideapplicators.Pressureregulators controlthesystempressurebyallowingpartofthe pumpoutputtoreturntothetankandalsorelieves excesspressurewhentheboomisnotinoperation. Aspressureisanintegralpartofcalibration,an accurate,easilyreadgaugeisessential.Liquid-filled gaugesaremoreeasytoreadastheyarelesssubject tominorpressurefluctuationsandvibrations.Both regulatorsandgaugesshouldbeineasyreachofthe operator.BoomsBoomsofawidevarietymaybefoundinthe citrusindustry,andarefrequentlylocallyconstructed andadaptedtotheneedsoftheparticulargrove operation.Theirconstructionshould,however, incorporatecertainfeaturesincluding: sufficientlengthtocovertheareabetweenthe treetrunkandtheoutertreecanopysothatgood sprayoverlapofthetreemiddleisobtained protectionfromlow-lyingtreelimbsintheform ofacoverorshieldwhileallowingforclear operatorvisibilityofthenozzlespraypatterns spring-loadedorhydraulicflexibilitytoprotect boomoncontactwithobstructionssuchastree trunksandlargewoodyweedspecies,while allowingitsreturntonormaloperation automaticallyandrapidly versatilitysuchasdoubleplumbingtoallowthe applicationofdifferentratesthrougheachoftwo boomswhenyoungresetsrequirelowerherbicide ratesthanoldertrees.Suchversatilitymightalso extendtotheuseoftwotanks,eachservicedby separateboomsfortheapplicationofseparate herbicidesinsequencesuchasRoundupandsoil residualsNozzlesNozzletypes,toonumeroustodescribehere,are listedwithdetailedspecificationsinvariouscatalogs, mostnotablythoseofSprayingSystemsandDelavan.FlatFanNozzleFlatfannozzletipsproduceataperededge patternwithgoodspraypenetration.Theyshouldbe operatedatpressuresof15to30psiwiththe emissionofmediumtocoarsedropletslesslikelyto driftthanfinedropletsathigherpressures.Nozzles shouldbeplacedon8to10inchcentersontheboom atanoperatingheightof8to12inches.Aspray patternoverlapof30%to50%issuggestedfor uniformspraycoverageofthesprayedsurface.Tipsin severalspraypatternanglesmaybeselectedincluding 80and110degrees.FloodingFlatFanNozzlesFloodingflatfannozzletipsproducewideangle, flatfanpatternssuitablefortheapplicationof herbicidesandmixturesofherbicidesandfertilizers. Theoptimumpressurerangeis15to20psiwhen spaced10to12inchesapartontheboom.Unlikethe ordinaryflatfannozzletips,increasedpressure increasesthespraypatternwidth.Boomheightshould beadjustedtoallowfor100%sprayoverlap.Because oftheirlargerorifices,thesetipsarelesslikelyto becomeplugged.Off-CenterNozzlesOff-centernozzlesproduceanoff-centerspray patternofrelativelyuniformdistribution.Theyare usuallyplacedatthebottomoftheboomtogive extendedcoveragebeyondthetreeline.Theyshould bemounted2to4inchesbeyondthelastmainnozzle andmountedonaswivelbody.Suchnozzlesshould beatleastasizeortwolargerthantheothernozzles andadjustedtocover1-1/2theareaoftheflatfan.

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HerbicideCalibrationandApplication Page3OtherTypeNozzlesInadditiontothenozzletypescommonlyusedin citrusweedcontrol,anumberofothersincludinglow volumeatomizingandrotaryatomizingtypesare beingevaluated.Theselowvolumenozzlesarebeing usedtoevaluatelowerapplicationratesofsystemic herbicidessuchasglyphosate,predominately.Before reliableconclusionscanbedrawn,thesenozzles shouldbeevaluatedatdifferentdosageratesandon differentweedspeciesatdifferentstagesofmaturity andvaryingweedstanddensity.Forexample,topkill orbrownoutwithsubsequentregrowthofaperennial grassspeciesshouldnotbeconfusedwithtotalkill whennorecoverytakesplace.NozzleConstructionandCareNozzletipsareavailableinavarietyofmaterials includingbrass,stainlesssteel,hardenedstainlesssteel andplastic(nylon).Brassistheleastexpensivebut wearsquicklywhenabrasivewettablepowdersare used.Suchorificewearwillresultinincreasedoutput and,therefore,incorrectapplicationrates.Stainless steelnozzletipswillnotwearasquicklyandnothave tobechangedasfrequently.Nozzletipsshouldnever becleanedwithmetallicobjects,butwitha toothbrushortoothpick.CALIBRATIONInitial,andthereafterperiodic,accurate calibrationofherbicideapplicationequipmentisan essentialcomponentofasuccessfulweedcontrol program.Afteryouhaveselectedthenozzletypesfor theequipment,selectthenozzlesizebasedonthe deliveryrateingallonsperacre(GPA)desired.To selectthenozzlesizeusethegallonsperminute (GPM)calculation.FieldCalibration1.Selectaspeedbetween2and4mph. 2.Selectagearwhichwillgiveyouthisspeedwith theenginerunningatleast1500rpmtoget adequatebypassagitation. 3.Determinethesizeofthenozzlerequiredforthe desiredgallonsperacre.Therequiredoutputcan becalculatedwiththeformulashowninEquation 1: 4.Fromthenozzlemanufacturer'stables,andata pressurebetween30and40psi,selectanozzle sizenearesttherequiredoutput. 5.Withnozzlesdischargingatselectedenginespeed, setpressureasdeterminedinstep3. 6.Measureatleast1/10acre(4356sq.ft.)forthe purposeofcalibration.Forexample,a4ft. sprayedwidthwouldrequire4356/4=1089ft 7.Fillthetankwithwater. 8.Spraytestareaatselectedgroundspeedand pressure. 9.Refillthetanktotheoriginallevelandrecord gallonssprayed.UsetheformulainEquation2to determinegallonsperacreoutput. StationaryCalibration1.Setthepressurebetween30and40psiwith nozzlesdischarging.

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HerbicideCalibrationandApplication Page42.Place1galloncansundereachofthefunctional nozzles. 3.Recordnumberofsecondsfornozzlestofillcans. 4.Determinegallonsperminutedeliveredfrom nozzlesbydividingthenumberofsecondsinto 60. UsetheformulasinEquation3,Equation4, Equation5andEquation6todeterminegallonsper acre(GPA): Usinga12-inchnozzlespacing,forexample: RESETS WaterRingApplicationThereareseveralproductsavailabletogrowers thatcanbeusedinwaterringsasadrenchtreatment. Ifratesarenotgivenforadrenchtreatment,thenthe rateperacremustbeusedasaguideline.Itisvery easytoover-dosetreesinawaterringwithadrench. Notonlymayyoube5to10timesoverthe recommendedrate,butyouwouldalsobeforcingthe productintotherootzoneofthetreeandsaturating thatrootarea.Ifawettablepowderisbeingused,the tankmusthaveanagitationsystem.WaterRingCalibrationHereareseveralstepstodetermineproperwater ringdrenchtreatmentamounts. 1.Determineareaofthewaterring-theareaofa circleis3.14xradiussquared(theradiusofthe distancefromtrunktoring). 2.Knowexactlyhowmuchwaterwillbeappliedto eachtree-usea5gallonbucketifnecessary. 3.Determinetheareacoveredby1tankofwater. (Gallonintank/gallonspertree,thenmultiply thisbytheareaofthewaterring.) 4.Determinewhatpartofanacrethisis:area coveredbyonetank(answerto#3)/43560 sq.ft./acre. 5.Taketherecommendedrateperacreand multiplytotheanswerto#4andaddthisamount tothetank.

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HerbicideCalibrationandApplication Page5EXAMPLE:Youhavea500gallonwatertank; youareapplying5gallonspertree,andthe recommendedrateofthematerialis5lbs.peracre. Yourwaterringis4ft.across. 1.3.14x2sq.=3.14x4= about12.5sq.ft. 2.5gallonspertree. 3.500gallons/5gallonspertree=100trees.100 treesx12.5sq.ft.=1250sq.ft.pertank. 4.1250/43560=.029or.03acres. 5..03acresx5lbs./acre=.15lbs..15lbs.isthe properamounttoaddtothetank.Toconvertthis toounces,multiply.15lbsx16oz./lb.=2.4oz. 2.4oz.maynotseemlikemuch,butitwouldbe theequivalentof5lbs./acre. Youcanseehowimportantitistoknowexactly howmuchwaterisgoingintoeachring.Ifyouwere toapply10gal.pertree,onlyhalftheareajust determinedwouldbecovered,andonly1.2oz.of productwouldbeneeded.TANKMIXINGTankmixingusuallyinvolvespesticidesandsome kindofliquidcarrier,mostcommonlywater. HerbicideformulationsusedinFloridacitrusinclude: wettablepowders(WP),whicharedryproducts thatdisperseinthecarrierandmustbekeptin suspensionbyagitation waterdispersiblegranules(WDG),smallpellets thatwetquicklyanddisperseeasilyinthecarrier flowableliquids(L)orsuspensions,whichmix relativelyeasily emulsifiableconcentrates(EC),oil-likeliquids thatdispersequicklyinthecarrier truewatersolubleliquidformulations dryflowables(DF) Forbestdispersionanduniformityinthetank mixture,wettablepowdersandwaterdispersible granulesshouldbeaddedfirstto1/4to1/2filled tank,followedbythoroughagitation.Flowableliquids, emulsifiableconcentrates,liquids,andsurfactants shouldbeaddedtothetanklastly.MISAPPLICATIONOF HERBICIDESMisapplicationofherbicidesorpesticidecan damageorkilldesirableplantsandcitrustrees, ultimatelycauseundesirableenvironmentaleffects, andpossiblyresultinlegalproceedings.Problemscan arisefollowingtheapplicationofherbicidesattohigh arate,tooclosetodesirablevegetationespecially susceptibletotheparticularherbicides,onsloping terrainwhereheavyrainfallcanmovethechemical intotherootzonesofdesirableplants. Iftheproblemofmisapplicationisdetected immediately,thenthetreatedsoilsurfacelayersmay beremoved,althoughasomewhatlaboriousprocess. Ifsometimehaselapsed,thenactivatedcharcoalmay beincorporatedintothesurfacesoilattherateof about7lbs.per1000sq.ft.Ifdamagetodesirable plantsisalreadyapparent,atrenchingmachinemay havetobeemployedtosevertherootsystemofthe plantsthatareincontactwiththecontaminating chemical.Hopefully,thiswillminimizefurther absorptionofthechemical,althoughsometimes correctiveactionisfutile.Cautionwoulddictatethat noherbicidebeusedwithinadistanceofthreetimes thecanopyradiusofdesirableplants.Sterilantrates ofherbicideappliedtoditchbanksborderingcitrus grovescanresultintreeinjurywhererootspermeate theareatobesprayed.Donotmixordisposeof herbicidemixesinareasnearwatersourcessuchas wells,ponds,andlakesoringrovelocationswhere treerootswouldbeintheareaofthedischarged material. Inordertoreducetheimpactofherbicidesonthe environmentoutsidetheimmediatetargetarea, effortsshouldbedirectedtowards: minimizingdriftbynotapplyingunderwindy conditionsandusinglowpressuresand,if necessary,driftcontroladditives minimizingapplicationconcentrationswithin recommendedrangesforweedcontrol betterirrigationmanagementtoreduceleaching monitoringdrainageoutflowstodeterminelevels ofherbicidesinwater

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HerbicideCalibrationandApplication Page6 erosioncontroltoavoidmovementofexcessive amountsofsurfaceappliedchemicalsintoponds, lakes,andwaterways thoroughon-sitecleanuptoavoidtreedamage andcontaminationofadjacentwatersources maintainingcropresiduelevelswithinthe approvedrangesbykeepingapplicationrates withinrecommendedrangesandavoiding excessiveherbicidespraycontactwithfruiton trees.