the term herbicide is used herein to mean an active ingredient that kills , controls or otherwise adversely modifies the growth of plants . an herbicidally effective or vegetation controlling amount is an amount of active ingredient which causes an adversely modifying effect and includes deviations from natural development , killing , regulation , desiccation , retardation , and the like . the terms plants and vegetation include germinating seeds , emerging seedlings and established vegetation . herbicidal activity is exhibited by the compounds of the synergistic mixture when they are applied directly to the plant or to the locus of the plant at any stage of growth or before planting or emergence . the effect observed depends upon the plant species to be controlled , the stage of growth of the plant , the application parameters of dilution and spray drop size , the particle size of solid components , the environmental conditions at the time of use , the specific compound employed , the specific adjuvants and carriers employed , the soil type , and the like , as well as the amount of chemical applied . these and other factors can be adjusted as is known in the art to promote non - selective or selective herbicidal action . generally , it is preferred to apply the composition of the present invention postemergence to relatively immature undesirable vegetation to achieve the maximum control of weeds . the substituted phenoxy alkanoic acid derivatives in which r is ch 3 contain asymmetric carbon atoms and are capable of existing as a racemic mixture such as dichlorprop or as an individual enantiomer or an enriched enantiomeric mixture such as dichlorprop - p by substituted phenoxy alkanoic acid derivatives and glyphosate derivatives is meant the acids themselves and their agriculturally acceptable esters and salts . suitable salts include those derived from alkali or alkaline earth metals and those derived from ammonia and amines . preferred cations include sodium , potassium , magnesium , and aminium cations of the formula : wherein r 1 , r 2 , and r 3 each , independently represents hydrogen or c 1 - c 12 alkyl , c 3 - c 12 alkenyl or c 3 - c 12 alkynyl , each of which is optionally substituted by one or more hydroxy , c 1 - c 4 alkoxy , c 1 - c 4 alkylthio or phenyl groups , provided that r 1 , r 2 , and r 3 are sterically compatible . preferred amine salts are those derived from ammonia , methylamine , dimethylamine , trimethylamine , isopropylamine , monoethanolamine , diethanolamine , triethanolamine , triisopropanolamine , 2 - methylthiopropylamine , bisallylamine , 2 - butoxyethylamine , morpholine , cyclo - dodecylamine , or benzylamine . amine salts are often preferred because they are water - soluble and lend themselves to the preparation of desirable aqueous based herbicidal compositions . suitable esters include those derived from c 1 - c 12 alkyl , c 3 - c 12 alkenyl or c 3 - c 12 alkynyl alcohols , such as methanol , iso - propanol , butanol , 2 - ethylhexanol , butoxyethanol , methoxypropanol , allyl alcohol , propargyl alcohol or cyclohexanol . in the composition of this invention , the weight ratio on an acid equivalent basis of the substituted phenoxy alkanoic acid component to glyphosate component at which the herbicidal effect is synergistic lies within the range of between about 5 : 1 and about 1 : 48 . preferably the weight ratio of the substituted phenoxy alkanoic acid component to the glyphosate component lies within the range of between about 3 : 1 and about 1 : 12 with a weight ratio of between about 1 : 1 and about 1 : 12 being especially preferred . the rate at which the synergistic composition is applied will depend upon the particular type of weed to be controlled , the degree of control required , and the timing and method of application . in general , the composition of the invention can be applied at an application rate of between about 100 grams of acid equivalents per hectare ( g ae / ha ) and about 2000 g ae / ha based on the total amount of active ingredients in the composition . an application rate between about 200 g ae / ha and about 1000 g ae / ha is preferred . in an especially preferred embodiment of the invention , the 2 , 4 - d component is applied at a rate between about 35 g ae / ha and about 560 g ae / ha , the dichlorprop component is applied at a rate between about 35 g ae / ha and about 280 g ae / ha and the glyphosate component is applied at a rate between about 100 g ae / ha and about 750 g ae / ha . the components of the synergistic mixture of the present invention can be applied either separately or as part of a multipart herbicidal system . the synergistic mixture of the present invention can be applied in conjunction with one or more other herbicides to control a wider variety of undesirable vegetation . when used in conjunction with other herbicides , the composition can be formulated with the other herbicide or herbicides , tank mixed with the other herbicide or herbicides or applied sequentially with the other herbicide or herbicides . some of the herbicides that can be employed in conjunction with the synergistic composition of the present invention include : amide herbicides such as allidochlor , beflubutamid , benzadox , benzipram , bromobutide , cafenstrole , cdea , chlorthiamid , cyprazole , dimethenamid , dimethenamid - p , diphenamid , epronaz , etnipromid , fentrazamide , flupoxam , fomesafen , halosafen , isocarbamid , isoxaben , napropamide , naptalam , pethoxamid , propyzamide , quinonamid and tebutam ; anilide herbicides such as chloranocryl , cisanilide , clomeprop , cypromid , diflufenican , etobenzanid , fenasulam , flufenacet , flufenican , mefenacet , mefluidide , metamifop , monalide , naproanilide , pentanochlor , picolinafen and propanil ; arylalanine herbicides such as benzoylprop , flampropand flamprop - m ; chloroacetanilide herbicides such as acetochlor , alachlor , butachlor , butenachlor , delachlor , diethatyl , dimethachlor , metazachlor , metolachlor , s - metolachlor , pretilachlor , propachlor , propisochlor , prynachlor , terbuchlor , thenylchlor and xylachlor ; sulfonanilide herbicides such as benzofluor , perfluidone , pyrimisulfan and profluazol ; sulfonamide herbicides such as asulam , carbasulam , fenasulam and oryzalin ; antibiotic herbicides such as bilanafos ; benzoic acid herbicides such as chloramben , dicamba , 2 , 3 , 6 - tba and tricamba ; pyrimidinyloxybenzoic acid herbicides such as bispyribac and pyriminobac ; pyrimidinylthiobenzoic acid herbicides such as pyrithiobac ; phthalic acid herbicides such as chlorthal ; picolinic acid herbicides such as aminopyralid , clopyralid and picloram ; quinolinecarboxylic acid herbicides such as quinclorac and quinmerac ; arsenical herbicides such as cacodylic acid , cma , dsma , hexaflurate , maa , mama , msma , potassium arsenite and sodium arsenite ; benzoylcyclohexanedione herbicides such as mesotrione , sulcotrione , tefuryltrione and tembotrione ; benzofuranyl alkylsulfonate herbicides such as benfuresate and ethofumesate ; carbamate herbicides such as asulam , carboxazole chlorprocarb , dichlormate , fenasulam , karbutilate and terbucarb ; carbanilate herbicides such as barban , bcpc , carbasulam , carbetamide , cepc , chlorbufam , chlorpropham , cppc , desmedipham , phenisopham , phenmedipham , phenmedipham - ethyl , propham and swep ; cyclohexene oxime herbicides such as alloxydim , butroxydim , clethodim , cloproxydim , cycloxydim , profoxydim , sethoxydim , tepraloxydim and tralkoxydim ; cyclopropylisoxazole herbicides such as isoxachlortole and isoxaflutole ; dicarboximide herbicides such as benzfendizone , cinidon - ethyl , flumezin , flumiclorac , flumioxazin and flumipropyn ; dinitroaniline herbicides such as benfluralin , butralin , dinitramine , ethalfluralin , fluchloralin , isopropalin , methalpropalin , nitralin , oryzalin , pendimethalin , prodiamine , profluralin and trifluralin ; dinitrophenol herbicides such as dinofenate , dinoprop , dinosam , dinoseb , dinoterb , dnoc , etinofen and medinoterb ; diphenyl ether herbicides such as ethoxyfen ; nitrophenyl ether herbicides such as acifluorfen , aclonifen , bifenox , chlomethoxyfen , chlomitrofen , etnipromid , fluorodifen , fluoroglycofen , fluoronitrofen , fomesafen , furyloxyfen , halosafen , lactofen , nitrofen , nitrofluorfen and oxyfluorfen ; dithiocarbamate herbicides such as dazomet and metam ; halogenated aliphatic herbicides such as alorac , chloropon , dalapon , flupropanate , hexachloroacetone , iodomethane , methyl bromide , monochloroacetic acid , sma and tca ; imidazolinone herbicides such as imazamethabenz , imazamox , imazapic , imazapyr , imazaquin and imazethapyr ; inorganic herbicides such as ammonium sulfamate , borax , calcium chlorate , copper sulfate , ferrous sulfate , potassium azide , potassium cyanate , sodium azide , sodium chlorate and sulfuric acid ; nitrile herbicides such as bromobonil , bromoxynil , chloroxynil , dichlobenil , iodobonil , ioxynil and pyraclonil ; organophosphorus herbicides such as amiprofos - methyl , anilofos , bensulide , bilanafos , butamifos , 2 , 4 - dep , dmpa , ebep , fosamine , glufosinate and piperophos ; phenoxy herbicides such as bromofenoxim , clomeprop , 2 , 4 - deb , 2 , 4 - dep , difenopenten , disul , erbon , etnipromid , fenteracol and trifopsime ; phenoxyacetic herbicides such as 4 - cpa , 3 , 4 - da , mcpa - thioethyl and 2 , 4 , 5 - t ; phenoxybutyric herbicides such as 4 - cpb , 3 , 4 - db , and 2 , 4 , 5 - tb ; phenoxypropionic herbicides such as cloprop , 4 - cpp , 3 , 4 - dp and fenoprop ,; aryloxyphenoxypropionic herbicides such as chlorazifop , clodinafop , clofop , cyhalofop , diclofop , fenoxaprop , fenoxaprop - p , fenthiaprop , fluazifop , fluazifop - p , haloxyfop , haloxyfop - p , isoxapyrifop , metamifop , propaquizafop , quizalofop , quizalofop - p and trifop ; phenylenediamine herbicides such as dinitramine and prodiamine ; pyrazolyl herbicides such as benzofenap , pyrazolynate , pyrasulfotole , pyrazoxyfen , pyroxasulfone and topramezone ; pyrazolylphenyl herbicides such as fluazolate and pyraflufen ; pyridazine herbicides such as credazine , pyridafol and pyridate ; pyridazinone herbicides such as brompyrazon , chloridazon , dimidazon , flufenpyr , metflurazon , norflurazon , oxapyrazon and pydanon ; pyridine herbicides such as cliodinate , dithiopyr , fluoroxypyr , haloxydine , picolinafen , pyriclor , thiazopyr and triclopyr ; pyrimidinediamine herbicides such as iprymidam and tioclorim ; quaternary ammonium herbicides such as cyperquat , diethamquat , difenzoquat , diquat , morfamquat and paraquat ; thiocarbamate herbicides such as butylate , cycloate , di - allate , eptc , esprocarb , ethiolate , isopolinate , methiobencarb , molinate , orbencarb , pebulate , prosulfocarb , pyributicarb , sulfallate , thiobencarb , tiocarbazil , tri - allate and vernolate ; thiocarbonate herbicides such as dimexano , exd and proxan ; thiourea herbicides such as methiuron ; triazine herbicides such as dipropetryn , triaziflam and trihydroxytriazine ; chlorotriazine herbicides such as atrazine , chlorazine , cyanazine , cyprazine , eglinazine , ipazine , mesoprazine , procyazine , proglinazine , propazine , sebuthylazine , simazine , terbuthylazine and trietazine ; methoxytriazine herbicides such as atraton , methometon , prometon , secbumeton , simeton and terbumeton ; methylthiotriazine herbicides such as ametryn , aziprotryne , cyanatryn , desmetryn , dimethametryn , methoprotryne , prometryn , simetryn and terbutryn ; triazinone herbicides such as ametridione , amibuzin , hexazinone , isomethiozin , metamitron and metribuzin ; triazole herbicides such as amitrole , cafenstrole , epronaz and flupoxam ; triazolone herbicides such as amicarbazone , bencarbazone , carfentrazone , flucarbazone , propoxycarbazone , sulfentrazone and thiencarbazone - methyl ; triazolopyrimidine herbicides such as cloransulam , diclosulam , florasulam , flumetsulam , metosulam , penoxsulam and pyroxsulam ; uracil herbicides such as butafenacil , bromacil , flupropacil , isocil , lenacil and terbacil ; 3 - phenyluracils ; urea herbicides such as benzthiazuron , cumyluron , cycluron , dichloralurea , diflufenzopyr , isonoruron , isouron , methabenzthiazuron , monisouron and noruron ; phenylurea herbicides such as anisuron , buturon , chlorbromuron , chloreturon , chlorotoluron , chloroxuron , daimuron , difenoxuron , dimefuron , diuron , fenuron , fluometuron , fluothiuron , isoproturon , linuron , methiuron , methyldymron , metobenzuron , metobromuron , metoxuron , monolinuron , monuron , neburon , parafluoron , phenobenzuron , siduron , tetrafluoron and thidiazuron ; pyrimidinylsulfonylurea herbicides such as amidosulfuron , azimsulfuron , bensulfuron , chlorimuron , cyclosulfamuron , ethoxysulfuron , flazasulfuron , flucetosulfuron , flupyrsulfuron , foramsulfuron , halosulfuron , imazosulfuron , mesosulfuron , nicosulfuron , orthosulfamuron , oxasulfuron , primisulfuron , pyrazosulfuron , rimsulfuron , sulfometuron , sulfosulfuron and trifloxysulfuron ; triazinylsulfonylurea herbicides such as chlorsulfuron , cinosulfuron , ethametsulfuron , iodosulfuron , metsulfuron , prosulfuron , thifensulfuron , triasulfuron , tribenuron , triflusulfuron and tritosulfuron ; thiadiazolylurea herbicides such as buthiuron , ethidimuron , tebuthiuron , thiazafluoron and thidiazuron ; and unclassified herbicides such as acrolein , allyl alcohol , aminocyclopyrachlor , azafenidin , benazolin , bentazone , benzobicyclon , buthidazole , calcium cyanamide , cambendichlor , chlorfenac , chlorfenprop , chlorflurazole , chlorflurenol , cinmethylin , clomazone , cpmf , cresol , ortho - dichlorobenzene , dimepiperate , endothal , fluoromidine , fluridone , fluorochloridone , flurtamone , fluthiacet , indanofan , methazole , methyl isothiocyanate , nipyraclofen , och , oxadiargyl , oxadiazon , oxaziclomefone , pentachlorophenol , pentoxazone , phenylmercury acetate , pinoxaden , prosulfalin , pyribenzoxim , pyriftalid , quinoclamine , rhodethanil , sulglycapin , thidiazimin , tridiphane , trimeturon , tripropindan and tritac . the synergistic composition of the present invention is particularly useful when used on glyphosate - tolerant , glufosinate - tolerant , 2 , 4 - d - tolerant , dicamba - tolerant or imiazolinone - tolerant crops . it is generally preferred to use the synergistic composition of the present invention in combination with herbicides that are selective for the crop being treated and which complement the spectrum of weeds controlled by these compounds at the application rate employed . it is further generally preferred to apply the synergistic composition of the present invention and other complementary herbicides at the same time , either as a combination formulation or as a tank mix . the synergistic composition of the present invention can generally be employed in combination with known herbicide safeners , such as benoxacor , benthiocarb , brassinolide , cloquintocet ( mexyl ), cyometrinil , daimuron , dichlormid , dicyclonon , dimepiperate , disulfoton , fenchlorazole - ethyl , fenclorim , flurazole , fluxofenim , furilazole , isoxadifen - ethyl , mefenpyr - diethyl , mg 191 , mon 4660 , naphthalic anhydride ( na ), oxabetrinil , r29148 and - phenyl - sulfonylbenzoic acid amides , to enhance their selectivity . in practice , it is preferable to use the synergistic composition of the present invention in mixtures containing an herbicidally effective amount of the herbicidal components along with at least one agriculturally acceptable adjuvant or carrier . suitable adjuvants or carriers should not be phytotoxic to valuable crops , particularly at the concentrations employed in applying the compositions for selective weed control in the presence of crops , and should not react chemically with herbicidal components or other composition ingredients . such mixtures can be designed for application directly to weeds or their locus or can be concentrates or formulations that are normally diluted with additional carriers and adjuvants before application . they can be solids , such as , for example , dusts , granules , water dispersible granules , or wettable powders , or liquids , such as , for example , emulsifiable concentrates , solutions , emulsions or suspensions . suitable agricultural adjuvants and carriers that are useful in preparing the herbicidal mixtures of the invention are well known to those skilled in the art . liquid carriers that can be employed include water , toluene , xylene , petroleum naphtha , crop oil , acetone , methyl ethyl ketone , cyclohexanone , trichloroethylene , perchloroethylene , ethyl acetate , amyl acetate , butyl acetate , propylene glycol monomethyl ether and diethylene glycol monomethyl ether , methanol , ethanol , isopropanol , amyl alcohol , ethylene glycol , propylene glycol , glycerine , n - methylpyrrolidinone , n — n - dimethylalkylamides , dimethyl sulfoxide and the like . water is generally the carrier of choice for the dilution of concentrates . suitable solid carriers include talc , pyrophyllite clay , silica , attapulgus clay , kaolin clay , kieselguhr , chalk , diatomaceous earth , lime , calcium carbonate , bentonite clay , fuller &# 39 ; s earth , cotton seed hulls , wheat flour , soybean flour , pumice , wood flour , walnut shell flour , lignin , and the like . it is usually desirable to incorporate one or more surface - active agents into the compositions of the present invention . such surface - active agents are advantageously employed in both solid and liquid compositions , especially those designed to be diluted with carrier before application . the surface - active agents can be anionic , cationic or nonionic in character and can be employed as emulsifying agents , wetting agents , suspending agents , or for other purposes . typical surface - active agents include salts of alkyl sulfates , such as diethanol - ammonium lauryl sulfate ; alkylarylsulfonate salts , such as calcium dodecyl - benzenesulfonate ; alkylphenol - alkylene oxide addition products , such as nonylphenol - c 18 ethoxylate ; alcohol - alkylene oxide addition products , such as tridecyl alcohol - c 16 ethoxylate ; soaps , such as sodium stearate ; alkylnaphthalene - sulfonate salts , such as sodium dibutylnaphthalenesulfonate ; dialkyl esters of sulfosuccinate salts , such as sodium di ( 2 - ethylhexyl ) sulfosuccinate ; sorbitol esters , such as sorbitol oleate ; quaternary amines , such as lauryl trimethyl - ammonium chloride ; polyethylene glycol esters of fatty acids , such as poly - ethylene glycol stearate ; block copolymers of ethylene oxide and propylene oxide ; and salts of mono and dialkyl phosphate esters . other adjuvants commonly used in agricultural compositions include compatibilizing agents , antifoam agents , sequestering agents , neutralizing agents and buffers , corrosion inhibitors , dyes , odorants , spreading agents , penetration aids , sticking agents , dispersing agents , thickening agents , freezing point depressants , antimicrobial agents , and the like . the compositions may also contain other compatible components , for example , other herbicides , plant growth regulants , fungicides , insecticides , and the like and can be formulated with liquid fertilizers or solid , particulate fertilizer carriers such as ammonium nitrate , urea and the like . the concentration of the active ingredients in the synergistic composition of the present invention is generally from 0 . 001 to 98 percent by weight . concentrations from 0 . 01 to 90 percent by weight are often employed . in compositions designed to be employed as concentrates , the active ingredients are generally present in a concentration from 5 to 98 weight percent , preferably 10 to 90 weight percent . such compositions are typically diluted with an inert carrier , such as water , before application . the diluted compositions usually applied to weeds or the locus of weeds generally contain 0 . 0001 to 1 weight percent active ingredient and preferably contain 0 . 001 to 0 . 05 weight percent . the present compositions can be applied to weeds or their locus by the use of conventional ground or aerial dusters , sprayers , and granule applicators , by addition to irrigation water , and by other conventional means known to those skilled in the art . 2 , 4 - d ( dimethylamine salt ), dichlorprop ( potassium salt ) and glyphomax xrt ® herbicide ( isopropylamine salt ) alone and in combinations were applied to the foliage of rapidly growing plant material utilizing a track sprayer calibrated to deliver an application volume of 187 l / ha . treated plant material was maintained in a greenhouse that provided a 16 - hr photoperiod , supplemented with metal halide - generated light , set to provide a minimum of 500 μmolm − 2 s − 1 . the greenhouse was maintained at a temperature of 26 to 28 ° c . and a relative humidity of 50 to 70 %. assessment of herbicidal activity was performed visually 14 to 21 days after application . the expected growth reduction of plant species from the combination of herbicides was calculated utilizing the colby equation : where x is % of growth reduction of a weed at a given concentration of a herbicide ( or herbicide formulation ) and y is the % growth reduction of the same species and size weed at a given concentration of an independent herbicide ( or herbicide formulation ). tables i , ii , iii and iv contain the data for expected and actual herbicidal growth reduction caused by relevant individual herbicides and combinations of these herbicides on agronomically important weeds . a field study was conducted at church hill , md . where glyphosate - resistant horseweed ( erica , conyza canadensis ) had been observed for 2 - 3 years prior to the start of this study . the study design was a split - plot with 4 replications per treatment and each plot was 3 . 048 m wide and 9 . 144 m long . the environmental conditions at the time of application were as follows : air temperature , 22 ° c . ; wind speed , 6 kph ; wind direction , south ; releative humidity , 85 %; cloud cover , 80 %; target foliage moisture , none ; soil moisture , moist ; soil temperature at 5 cm depth , 21 ° c . the treatments were applied using a backpack co 2 sprayer , with six xr8003 flat fan nozzles spaced 46 cm apart ( boom length : 2 . 76 m ) and held 40 cm above the plant canopy . the sprayer was operated at 103 kpa and 4 . 8 kilometers per hour to deliver 187 l of water per hectare . at the time of applications the glyphosate - resistant horseweed were 30 - 38 cm tall and there were between 10 and 20 plants per square meter ( m 2 ). the percent visual control of glyphosate - resistant horseweed was rated over the entire plot ( 27 . 87 m 2 ) 29 days after application . in each plot between 278 and 557 glyphosate - resistant horseweed plants were rated , collectively , for percent visual control . the results are tabulated in table v . although the invention has been described with reference to preferred embodiments and examples thereof , the scope of the present invention is not limited only to those described embodiments . as will be apparent to persons skilled in the art , modifications and adaptations to the above - described invention can be made without departing from the spirit and scope of the invention , which is defined and circumscribed by the appended claims .
an herbicidal composition containing an herbicidal substituted phenoxy alkanoic acid derivative component and an herbicidal glyphosate component provides synergistic control of selected weeds .