where a range of values is provided , it is understood that each intervening value , to the tenth of the unit of the lower limit unless the context clearly dictates otherwise , between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the invention . the upper and lower limits of these smaller ranges may independently be included in the smaller ranges is also encompassed within the invention , subject to any specifically excluded limit in the stated range . where the stated range includes one or both of the limits , ranges excluding either both of those included limits are also included in the invention . unless defined otherwise , all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs . although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention , the preferred methods and materials are now described . it must be noted that as used herein and in the appended claims , the singular forms “ a ,” “ and ” and “ the ” include plural references unless the context clearly dictates otherwise . thaxtomin utilized in this invention may be derived in fermentation of the following actinomycetes cultures : s . scabies — atcc 49173 , s . acidiscabies — atcc 49003 and bl37 - eq - 010 — or it can be purchased from commercial sources . the thaxtomin utilized in the invention include but are not limited to agents described as cyclic dipeptides having the basic structure cyclo -( l - 4 - nitrotryptophyl - l - phenylalanyl ). in embodiments , suitable diketopiperazne moieties may be n - methylated , and include congeners carrying phenylalanyl alpha andring - carbon hydroxyl groups . the chemical in a particular embodiment comprises : wherein r 1 is methyl or h , r 2 is hydroxy or h , r 3 is methyl or h , r 4 is hydroxy or h , r 5 is hydroxy or h , r 6 is hydroxy or h , and combinations thereof . non limiting examples of suitable thaxtomin is for use in accordance with the present invention include but are not limited to thaxtomin a , thaxtomin a ortho isomer , thaxtomin b , thaxtomin c , hydroxythaxtomin c , thaxtomin a p - isomer , hydroxythaxtomin a and des - n - methylthaxtomin c and derivatives of any of these ( see fig1 ). the compositions of the present invention may be sprayed on the plant or applied to soil . particular embodiments are described in the examples , infra . these compositions may be in the form of dust , coarse dust , micro granules , granules , wettable powder , emulsifiable concentrate , liquid preparation , suspension concentrate , water degradable granules or oil suspension . the compositions of the invention do comprise a carrier and / or diluent . the term , ‘ carrier ’ as used herein means an inert , organic or inorganic material , with which the active ingredient is mixed or formulated to facilitate its application to plant or other object to be treated , or its storage , transport and / or handling . examples of diluents or carriers for the pre - and post - emergence herbicides include , but are not limited to , water , milk , ethanol , mineral oil , glycerol . the compositions of the present invention may comprise at least two herbicidal agents . one herbicidal agent is thaxtomin set forth above . it may be present in one embodiment thaxtomin is present in an amount ranging from about 0 . 01 to about 5 . 0 mg / ml . the other herbicidal agent may be a bioherbicide and / or a chemical herbicide . the bioherbicide may be derived from a plant , or may be a microbial bioherbicide . in particular , the bioherbicide derived from a plant may be derived from pepper ( e . g ., sarmentine ) or may be a plant essential oil ( e . g ., lemongrass oil ). the microbial bioherbicide may be derived from bacteria ( e . g . streptomyces sp ., burkholderia sp ., particularly burkholderia sp . or fractions , supernatant , filtrate , or compounds derived therefrom which disclosed in wo / 2011 / 106491 and pct / us12 / 50807 , the contents of which are incorporated herein by reference or fungus . the bioherbicide may be selected from the group consisting of clove , cinnamon , lemongrass , citrus oils , orange peel oil , bialaphos , cornexistin , aal - toxin , leptospermone and other triketones ( such as 2 -( 2 - nitro - 4 - trifluoromethylbenzoyl ) cyclohexane - 1 , 3 - dione , flavesone , grandiflorone , etc . ), sarmentine or sarmentine analog , momilactone b , sorgoleone , ascaulatoxin , manuka oil , phoma macrostoma , d - limonene , m - tyrosine , tentoxin , nethylated seed oil , chelated iron , acetic acid and ascaulatoxin aglycone . in a particular embodiment , the composition may comprise thaxtomin , lemongrass oil and optionally a surfactant and / or vegetable oil . in another embodiment , the composition may comprise thaxtomin , sarmentine and optionally a nonionic surfactant and / or vegetable oil . in another particular embodiment , the composition may comprise thaxtomin , bialaphos ( also known as bialafos ) and optionally a nonionic surfactant and / or vegetable oil . the bioherbicide such as lemongrass oil , bialaphos ( bialfos ), manuka oil , sarmentine , sarmentine analog , burkholderia species may be present in an amount ranging from about 0 . 01 mg / ml to about 100 mg / ml and more preferably between about 0 . 025 mg / ml to about 50 mg / ml the chemical herbicide may be selected from the group consisting of 24 - d , acetochlor , acifluorfen , amicarbazone , anilofos , asulam , atrazine , bensulfuron , bentazone , byspiribac - sodium , carfentrazone , chlorthiamid , clomazone , cyhalofop - butyl , dicamba , diclofop . dithiopyr , diuron , eptc , fenoxaprop , flumioxazin , fluridone , fluroxypyr , fomesafen , glufosinate , glyphosate , halosulfuron , imazethapyr , indazifam , isoxaben , linuron , mcpa ( 4 - chloro - 2 - methylphenoxy acetic acid ), mcpp , mesotrione , metolachlor , metribuzin , msma , napropamide , nicosulfuron , norflurazon , oleic acid , oryzalin , oxadiazon , oxyfluorfen , quinclorac , pelargonic acid , pendimethalin , penoxsulam , picloram , propanil , pyrithrobac - sodium , rimsulfuron , saflufenacil , sethoxydim , simazine , sulcotrione , thiazopyr , thiencarbazone , thiobencarb , triclopyr , trifluralin , trioxysulfuron - sodium . the chemical herbicide such as pendimethalin or clomazone , atrazine , oryzalin , trifluralin and metolachlor may be present in a pre - emergent weed control application in an amount ranging from about 0 . 01 mg / ml to about 50 mg / ml and a chemical herbicide such as clomazone , cyhalofop , oryzalin , s - metolachlor , bispyribac - sodium , glyophosate , glufosinate , mesotione , penoxsulam , carfentrazone , quinclorac , triclopyr - ester , trioxysulfuron - sodium , thiobencarb , propanil , 2 , 4 - d , dicamba in a pre or post - emergent application from about 0 . 1 mg / ml to about 60 g a . i ./ ml or 0 . 03 kg a . i ./ ha to 5 . 6 kg a . i ./ ha . the composition may further comprise an adjuvant which may be vegetable oil comprising ethyl oleate , polyethylene dialkyl ester and ethoxylated nonylphenol . the composition may additionally comprise a surfactant to be used for the purpose of emulsification , dispersion , wetting , spreading , integration , disintegration control , stabilization of active ingredients , improvement of fluidity or rust inhibition . the choice of dispersing and emulsifying agents , such as non - ionic , anionic , amphoteric and cationic dispersing and emulsifying agents , and the amount employed is determined by the nature of the composition and the ability of the agent to facilitate the dispersion of the herbicidal compositions of the present invention . for post - emergent formulations , the formulation components used may contain smectite clays , attapulgite clays and similar swelling clays , thickeners such as xanthan gums , gum arabic and other polysaccharide thickeners as well as dispersion stabilizers such as nonionic surfactants ( for example polyoxyethylene ( 20 ) monolaurate or polysorbate 60 poe ( 20 ) sorbitan monostearate , ethylene glycol monostearate ). the concentration of the clays may vary between about 0 - 2 . 5 % w / w of the total formulation , the polysaccharide thickeners may range between about 0 - 0 . 5 % w / w of the total formulation and the surfactants may range from about 0 - 5 % w / w of the total formulation . the compounds , combinations and compositions set forth herein may be used to modulate the emergene and / or growth of various weeds and can thus be used in pre - emergent and post - emergent applications . said weeds may include but are not limited to echinochloa phyllopogon , echinochloa colona , echinochloa oryzoides , echinochloa crus - galli , schoenoplectus spp ., heteranthera spp ., monochoria spp ., bacopa spp ., sagittaria spp ., oryza punctata and oryza sativa ( weedy ). the application we filed also includes the following targets : chenopodium sp . ( e . g ., chenopodium album , chenopodium murale ), abutilon sp . ( e . g ., abutilon theophrasti ), helianthus sp . ( e . g ., helianthus annuus ), ambrosia sp . ( e . g ., ambrosia artemesifolia , ambrosia trifida ), amaranthus sp . ( e . g ., amaranthus retroflexus , amaranthus palmeri , amaranthus rudis , amaranthus spinosus , amaranthus tuberculatus ), convolvulus sp . ( e . g ., convolvulus arvensis ), brassica sp . ( e . g ., brassica kaber ), taraxacum sp . ( e . g ., taraxacum officinale ), solanum sp . ( e . g ., solanum nigrum , solanum elaeagnifolium , solanum physalifolium , solanum ptycanthum ), malva sp . ( e . g ., malva neglecta ), setaria sp . ( e . g ., setaria lutescens ), bromus sp . ( e . g ., bromus tectorum , bromus diandrus , bromus hordeaceus ), poa sp . ( e . g ., poa annua , poa pratensis ), lolium sp . ( e . g ., lolium perenne , lolium rigidum , lolium multiflorum l . var . pace ), festuca sp . ( e . g ., festuca arundinaceae , festuca rubra ), echinochloa sp . ( e . g ., echinochloa crus - galli , echinochloa colona ), and particularly , lambsquarter — chenopodium album , redroot pigweed — amaranthus retroflexus , wild mustard — brassica kaber , dandelion — taraxacum officinale , and black nightshade — solanum nigrum , oxalis sp . ( e . g ., oxalis stricta , oxalis pes - caprae , oxalis corniculata ); cyperus sp . ( e . g ., cyperus difformis ); conyza sp . ( e . g ., conyza canadensis , conyza sumatrensis , conyza bonariensis ); sagina sp . ( e . g ., sagina procumbens ); veronica sp . ( e . g ., veronica hederafolia ), stellaria sp . ( e . g ., stellaria media ), rorippa sp . ( e . g ., rorippa islandica ), senecio sp . ( e . g ., senecio vulgaris ), lamium sp . ( e . g ., lamium amplexicaule ), digitaria sp . ( e . g ., digitaria sanguinalis , digitaria ischaemum ), galium sp . ( e . g ., galium aparine ), galinsoga sp . ( e . g ., galinsoga aristatula ), cardamine sp . ( e . g ., cardamine flexuosa , cardamine hirsuta ), kochia sp . ( e . g ., kochia scoparia ), eleusine sp . ( e . g ., eleusine indica ), portulaca sp . ( e . g ., portulaca oleraceae ), plantago sp . ( e . g ., plantago lanceolata ), euphorbia sp . ( e . g ., euphornia supina , euphorbia maculate , euphorbia esula , euphorbia prostrata ), erodium sp . ( e . g ., erodium cicutarium ), sonchus sp ., ( e . g ., sonchus oleraceus ), lactuca sp . ( e . g ., lactuca serriola ), capsella sp . ( e . g ., capsella bursa - pastoris ), leptochloa sp . ( e . g ., leptochloa fascicularis , leptochloa virgata ), raphanus sp . ( e . g ., raphanus raphanistrum ), calandrinia sp . ( e . g ., calandrinia ciliata ), paspalum sp . ( e . g ., paspalum dilatatum ), gnaphalium sp ., cynodon sp . ( e . g ., cynodon dactylon , cynodon hirsutus ), polygonum sp . ( e . g ., polygonum arenastrum , polygonum lapathofolium ), avena fatua , hordeum sp . ( e . g ., hordeum leporinum ), urtica sp . ( e . g ., urtica urens ), tribulus terrestris , sisymbrium sp . ( e . g ., sisymbrium irio ), cenchrus sp ., salsola sp . ( e . g ., salsola tragus , salsola kali ), amsinckia sp . ( e . g ., amsinckia lycopsoides ), ipomoea sp ., claytonia perfoliata , polypogon sp . ( e . g ., polypogon monspeliensis ), xanthium sp ., hypochaeris radicata , physalis sp ., eragrostis sp ., verbascum sp ., chamomilla suaveolens , centaurea sp . ( e . g ., centaurea solstitialis ), epilobium brachycarpum , panicum sp . ( e . g ., panicum capilare , panicum dichotomiflorum ), rumex acetosella , eclipta sp . ( e . g ., eclipta alba , eclipta prostrata ), ludwigia sp ., urochloa sp . ( e . g . urochloa platyphylla , urochloa panicoides ), leersia sp ., sesbania sp . ( sesbania herbacea ), rotala sp ., ammania sp ., alternathera philoxeroides , commelina sp ., sorghum halepense , parthenium hysterophorus , chloris truncata the composition and method of the present invention will be further illustrated in the following , non - limiting examples . the examples are illustrative of various embodiments only and do not limit the claimed invention regarding the materials , conditions , weight ratios , process parameters and the like recited herein . in a pot study test in greenhouse conditions , 6 - inch corn plants ( zea mays var . sunglow ) were sprayed with increasing concentrations of thaxtomin a mixed in a carrier 4 % ethanol , 0 . 02 % polysorbate 60 poe ( 20 ) sorbitan monostearate solution . the spraying solutions contained 0 . 125 , 0 . 25 , 0 . 5 and 1 . 0 mg thaxtomin a / ml , and the plants are sprayed until total coverage . each treatment was done in three replicates , and a control solution consists of water with 4 % ethanol and 0 . 02 % polysorbate 60 poe ( 20 ) sorbitan monostearate as a surfactant . prior to and after treatments , plants are grown in a greenhouse under artificial lights ( 12 - h light / dark cycle ) at 25 ° c . plants are evaluated in one - week intervals starting at 7 days after treatment . the final evaluation is done three weeks after treatment , at which time point , no phytotoxicity is observed in any of the test plants even at the highest thaxtomin a concentration . a pot study is conducted to test the phytotoxicity of thaxtomin a on corn ( zea mays var . early sunglow ) and wheat ( triticum aestivum var . pr1404 ). to confirm the activity on broadleaf weeds , pigweed ( amaranthus sp .) is planted in the same pot with either three corn or five wheat seeds , and sprayed simultaneously with the cereal test plants . the less than 3 - inch tall plants grown under growth lights ( 12 - h light / 12 - h dark ) at 28 ° c . are sprayed with thaxtomin a solutions derived from a liquid culture of s . acidiscabies containing 0 . 5 , and 1 . 0 mg thaxtomin a per ml of solvent ( 4 % ethanol and 0 . 2 % non - ionic surfactant ). a solution of 4 % ethanol + 0 . 2 % non - ionic surfactant without thaxtomin a is used as a control treatment . each treatment is conducted in three replicates . treated plants are kept at 28 ° c . under growth lights and observed at three time points — 7 , 14 and 21 days after treatment — for visual symptoms of phytotoxicity on corn and wheat and % control of pigweed . at each time point , no symptoms of phytotoxicity are observed in the cereal plants treated with thaxtomin a . the highest concentration of thaxtomin a ( 1 . 0 mg / ml ) results in a complete control of pigweed grown in the same pots with corn and wheat . to test the phytotoxicity of thaxtomin a on sorghum plants , five seeds of sorghum ( sorghum bicolor ) are planted in each 4 ″× 4 ″ plastic pot filled with soil . plants were grown under optimal conditions in a greenhouse before and after treatment with solutions containing 0 . 5 and 1 . 0 mg thaxtomin a / ml . at the time of the treatment , the plants are about 3 inches tall . each treatment is applied in three replicates , and a control treatment included plants treated with just the carrier ( 4 % etoh , 0 . 02 % polysorbate 60 poe ( 20 ) sorbitan monostearate ). evaluations for phytotoxicity are performed at 7 - day intervals starting one week after treatment . the last evaluation is performed three weeks after the treatment at which point , no phytotoxicity is observed in the treated plants in any treatment concentration . a strain of s . acidiscabies ( atcc - 49003 ) is grown in oat bran broth for 5 days ( 25 ° c ., 200 rpm ). the whole cell broth with thaxtomin a is extracted using xad resin . the dried crude extract was resuspended in 4 % ethanol and 0 . 02 % non - ionic surfactant at a concentration of 10 mg / ml , and the solutions with two different concentrations of thaxtomin a ( 0 . 5 and 1 . 0 mg / ml ) are tested the following broadleaf weed species : fescue , tall —( festuca arundinaceae schreb . var . aztec ii , anthem ii , ls 1100 ) all plant species are tested in 4 ″× 4 ″ plastic pots in three replicates . the untreated control plants are sprayed with the carrier solution ( 4 % ethanol , 0 . 02 % glycosperse ) and the positive control plants with roundup at a rate corresponding to 1 fl . oz / acre . treated plants are kept in a greenhouse under 12 h light / 12 h dark conditions . data for broadleaf species from weekly evaluations are presented in table 1 . the extract from a bacterial culture of s . acidiscabies with a thaxtomin a concentration of 0 . 5 mg / ml or higher showed good efficacy (& gt ; 50 %) against at least three of the most common broadleaf weed species ( dandelion , mustard and pigweed ) in both cereal and turf growing systems . control of some weeds such as black nightshade and common lambsquarter was not complete but thaxtomin a even at the lower concentration ( 0 . 5 mg / ml ) results in severe stunting of these weeds . in this same study , no adverse effects are observed in grass species treated with either 0 . 5 or 1 . 0 mg / ml thaxtomin a . in all tested grass species , no phytotoxic effects were visible at even the higher thaxtomin a concentration . the combined effect of thaxtomin a and two commercial herbicides ( bipyribac - sodium formulated as regiment and lemongrass oil formulated as greenmatch ex ) on small - flower umbrella sedge and watergrass is tested in a field study using small ( 1 - sq foot ) plots . all single product treatments and tank mix combinations were sprayed at 57 gal per acre . evaluation of % control was done 14 days after treatment and the results are presented in table 2 below . means in each column marked with the same letter in table 2 are not statistically different from each other at p & lt ; 0 . 05 according to the results , lemongrass oil at 1 . 25 % weight does not improve the efficacy of thaxtomin a ( at 0 . 25 mg / ml ) on sedge but it significantly increases the efficacy on grass weeds such as watergrass ( field test ) and sprangletop ( greenhouse test ). according to the results , lemongrass oil at 1 . 25 % does not improve the efficacy of thaxtomin a ( at 0 . 25 mg / ml ) on sedge but it significantly increases the efficacy on grass weeds such as watergrass ( field test ) and sprangletop . thaxtomin a ( at 0 . 5 mg / ml ) improves the efficacy of an als inhibitor , bipyribac sodium ; used at half label rate on both sedge and grasses . the efficacy of thaxtomin a derived from a liquid culture of s . acidiscabies is tested in a field study on rice using 4 . 9 sq - ft plots surrounded by a metal ring . treatments with either thaxtomin a or thaxtomin a in combination with lemongrass oil ( formulated as greenmatch ex ) or cyhalofop ( formulated as clincher ca ) were done using a hand - held sprayer with a water volume corresponding to 57 gallons per acre . rice ( variety m209 ) was grown until maturity and harvested by hand for yield and weed count assessment . results of yield ( kg / ha ), and numbers of redstem , small - flower umbrella sedge , and sprangletop in each plot are presented in table 3 below . results indicate that thaxtomin at 180 g / acre significantly reduced the number of sedges but had no effect on sprangletop or yield . when used at half rate ( thaxtomin a 90 g / acre ), a combination with lemongrass oil had better effect on sedges than a combination with cyhalofop ( used at half label rate 52 g / acre ). good grass weed ( sprangletop ) control is achieved when thaxtomin ( 90 g / acre ) is combined with cyhalofop at half the label rate — this combination also improves the yield significantly . cyhalofop ( 2 -[ 4 -( 4 - cyano - 2 - fluorophenoxy ) phenoxy ] propanoic acid , butyl ester ) is also mixed together with adjuvant containing ethyl oleate , polyethylene dialky ester and ethoxylated nonylphenol ( 2 . 5 % v / v ) and increasing concentrations of thaxtomin a ( purified from the atcc strain 49003 ) at concentrations 0 . 1 , 0 . 2 and 0 . 4 mg / ml . the concentrations of the 2 -[ 4 -( 4 - cyano - fluorophenoxy ) phenoxy ] propanoic acid , butyl ester before dilution are 29 . 6 % ( 2 . 38 lb / gal ) and 21 . 7 % ( 2 lb / gal ), respectively . the effect of these mixtures on the growth of common water plantain , red stem , smallflower sedge and sprangletop is determined in the greenhouse . similarly , rice plants of variety m104 are grown and tested for phytotoxic effects , and all plants are evaluated 7 , 14 , and 21 days after treatment . results of from the study with cyhalofop formulated as clincher ca at the 21 - day evaluation point are presented in table 4 below . as a conclusion , clincher ca ( 29 . 6 % cyhalofop by weight ) applied at half label rate ( 6 . 5 oz / acre ) has good efficacy against grass weeds — not so good on broadleaves and poor on sedges . a combination of clincher ca ( cyhalofop ) and thaxtomin a provides good control of all rice weeds tested in this study . efficacy of thaxtomin a against grass weeds is substantially improved if combined with clincher . combination of thaxtomin a with clincher ca did not cause phytotoxicity on rice at any tested concentration . penoxsulam ( 2 -( 2 , 2 - difluoroethoxy )- n -( 5 , 8 - dimethoxy [ 1 , 2 , 4 ] triazolo [ 1 , 5c ] pyrimidin - 2 - yl )- 6 - trifluoromethyl ) benzenesulfonamide ) is mixed together with adjuvant containing ethyl oleate , polyethylene dialky ester and ethoxylated nonylphenol ( 2 . 5 % v / v ) and increasing concentrations of thaxtomin a ( purified from the atcc strain 49003 ) at concentrations 0 . 1 , 0 . 2 and 0 . 4 mg / ml . the concentrations of the 2 -[ 4 -( 4 - cyano - fluorophenoxy ) phenoxy ] propanoic acid , butyl ester or 2 -( 2 , 2 - difluoroethoxy )- n -( 5 , 8 - dimethoxy [ 1 , 2 , 4 ] triazolo [ 1 , 5c ] pyrimidin - 2 - yl )- 6 - trifluoromethyl ) benzenesulfonamide before dilution are 29 . 6 % ( 2 . 38 lb / gal ) and 21 . 7 % ( 2 lb / gal ), respectively . the effect of these mixtures on the growth of common water plantain , red stem , smallflower sedge and sprangletop is determined in the greenhouse . similarly , rice plants of variety m104 are grown and tested for phytotoxic effects , and all plants are evaluated 7 , 14 , and 21 days after treatment . a strain of s . acidiscabies was grown in oat bran broth for 5 days ( 25 ° c ., 200 rpm ). the whole cell broth was extracted using xad resin , and the dried crude extract was resuspended in 4 % ethanol and 0 . 2 % non - ionic surfactant at a concentration of 10 mg / ml . the diluted extracts containing 0 . 2 and 0 . 4 mg thaxtomin a per ml were tested on three weed species ( redstem ; ammania spp ., smallflower umbrella sedge ; cyperus difformis and sprangletop : leptochloa uninervia ). other treatments included sarmentine at 2 . 5 and 5 . 0 mg / ml , and a combination treatment containing 0 . 2 mg thaxtomin a and 2 . 5 mg sarmentine per ml . each treatment was applied in three replicates . treated plants were kept in a greenhouse under 12 h light / 12 h dark conditions . results from an evaluation performed 25 days after treatment are presented in table 5 . thaxtomin a at the highest concentration of 0 . 4 mg / ml provides excellent control of sedge but poor control of the grass weed ( sprangletop ). when combined with sarmentine , the efficacy against grass weeds improves significantly . also , efficacy against sedge is improved with the combination treatment compared with the single application of thaxtomin a alone at the corresponding concentration . in this study , the control of the broadleaf weed ( redstem ) is poor with all treatments . bialaphos is produced by bacteria streptomecyes spp . and its synthesized active ingredient glufosinate is marketed as rely ® 200 ( bayer cropscience , research triangle park , nc ). bialaphos has a non - selective property and inhibits the activity of glutamine synthetase , an enzyme involved in the synthesis of the amino acid glutamine . the mbi - 005 and bialaphos were prepared at various concentrations either as single ingredients or in combination with bialaphos . the treatments were applied at approximately ⅔ ml per replicate with a hand - help spray nozzle to barnyard grass or sedge . there were 3 replicates per treatment which were randomized after spray and were kept in a greenhouse at 25 ° c . for evaluation of phytotoxicity (% control ). when mbi - 005 was mixed with bialaphos , the efficacy was increased several times more than when they were used alone ( table 6 , 7 , and 8 ). at higher rates of the mixtures , 100 % control was achieved ( table 8 ). synergy was observed when bialaphos at 0 . 178 mg / ml was mixed with mbi - 005 at 0 . 25 mg / ml , and about 42 % efficacy was achieved when the rate of bialaphos was increased close to 1 . 0 mg / ml from 10 % control with bialaphos alone ( table 7 ). # synergy is calculated from colby &# 39 ; s formula ( colby , 1967 . weeds 15 : 20 - 22 ): ee = x + y − ( xy / 100 ) ( where e is the observed efficacy of product a + b , ee is expected efficacy of a + b , and x and y are the efficacy of product a or b when used alone . if e / ee & lt ; 1 the combination is antagonistic ; if e / ee = 1 the combination is additive ; if e / ee & gt ; 1 the combination is synergistic ). there were 3 replicates per treatment which were sprayed with approximately ⅔ ml per replicate . the treatments were completely randomized and kept in a greenhouse at 25 ° c . the efficacy was rated at 7 and 14 days post treatment . the results are shown in table 9 to 11 . for barnyard grass control , mbi - 005 had synergistic effects when combined with clomazone , ( penoxsulam , bispyribac - sodium , thiobencarb , and propanil ( table 9 ). mbi - 005 had additive effects when combined with cyhalofop , and fenoxaprop - p - ethyl ( table 10 ). mbi - 005 showed great synergy with glyphosate for controlling ragweed and also showed synergy with both turf herbicides . the synergistic effect of mbi - 005 with glufosinate ( synthetic bialaphos ) ( table 11 ) on crabgrass was likely less since the rate of mbi - 005 was too low . to further describe the spectrum of pre - emergence activity , tests were conducted in laboratory and field conditions . in laboratory testing , 35 seeds were placed on a ring of blotter paper inside a 3 cm petri dish and supplied with 4 ml of mbi - 005 (≦ 0 . 1 mg mbi - 005 / ml ). water was used as a negative control and oryzalin applied as a positive control . petri dishes were randomly placed in a growth room at 25 ° c . and 50 % rh . treatments were replicated three times and germinated seeds were counted 7 and 14 days after application ; water was added as necessary to maintain moisture levels inside each petri dish . in field testing , field soil containing weed seeds were treated with 38 . 2 l mbi - 005 / ha at a spray volume of 280 l / ha using a co2 sprayer with flat fan nozzles . treatments , including water as the negative control and gallery as the positive control , were replicated four times and applied twice at a four week interval . treatments were evaluated visually as % cover and above - ground fresh weights per container were taken . results in table 12 indicate broad spectrum activity on both annual grasses and broadleaves , as well as on some perennials . field results showing control over an eight - day period also suggest soil residual activity . to further describe the spectrum of post - emergence activity , tests were conducted in laboratory and field conditions . for laboratory testing , 3 - 10 plants ( depending on the species ) at the 1 - 2 leaf stage plants in 2 . 5 cm square pots containing sunshine mix no . 2 planting media were sprayed at 1 mg mbi - 005 / ml at a rate of 40 gal / a using a cabinet track sprayer . negative controls were sprayed with water and positive controls with glufosinate . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated five times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . in field testing , field soil containing weeds at the 1 - 5 leaf stage were treated with 38 . 2 l mbi - 005 / ha at a spray volume of 374 l / ha . treatments , including water as the negative control and weedbgon or preen broadleaf as the positive control , were replicated four times and applied twice at a four week interval . the positive control on late watergrass , ricefield bulrush , smallflower sedge and arrowhead was an herbicide containing as active ingredient 2 , 4 - d and an organosilicone surfactant was added to mbi - 005 . treatments were assessed for % control and % ground cover . results , shown in table 13 , indicate good ( between 80 and 100 % control ) post - emergence activity on annual many broadleaves and sedges , and limited post - emergent activity on annual grasses , unless surfactants are added . post - emergent control of perennials was generally limited except for oxalis pes - caprae . synergistic effects of mbi - 005 and manuka oil ( containing leptospermone and other triketones ) were evaluated on crabgrass seed germination in a laboratory experiment . thirty - five seeds were placed on a ring of blotter paper inside a 3 cm petri dish , covered with 10 cm 3 of inert baked clay particle media and supplied with 7 ml of 0 . 035 mg / ml mbi - 005 , a manuka oil concentration , or a combination of mbi - 005 and manuka oil ( fig2 ). water was used as a negative control . petri dishes were randomly placed in a growth room at 25 ° c . and 50 % rh . treatments were replicated three times and germinated seeds were counted 7 days after application ; water was added as necessary to maintain moisture levels inside each petri dish . synergy occurred between mbi - 005 and manuka oil at 0 . 003 % v / v . mild synergy was seen between mbi - 005 and manuka oil at 0 . 01 % v / v . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) reduction in germination using colby &# 39 ; s formula . results are shown in fig2 synergistic effects of mbi - 005 and m - tyrosine were evaluated on crabgrass seed germination in a laboratory experiment . forty - five seeds were placed on a ring of blotter paper inside a 3 cm petri dish , covered with 10 cm 3 of inert baked clay particle media and supplied with 7 ml of 0 . 035 mg / ml mbi - 005 , a m - tyrosine concentration , or a combination of mbi - 005 and m - tyrosine ( table 14 ). water was used as a negative control . petri dishes were randomly placed in a growth room at 25 ° c . and 50 % rh . treatments were replicated three times and germinated seeds were counted 7 days after application ; water was added as necessary to maintain moisture levels inside each petri dish . synergy occurred between mbi - 005 and m - tyrosine at 0 . 44 mg / ml but not for mbi - 005 and m - tyrosine at 22 mg / ml . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) reduction in germination using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and chelated iron were evaluated on crabgrass at the 1 - 2 leaf stage in a laboratory experiment . ten seedlings in 2 . 5 cm square pots containing plant growth mix were sprayed with two suboptimal rates of mbi - 005 , 14 . 49 mg / ml of chelated fe , or a combination thereof , at a volume of 40 gal / a using a cabinet track sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated five times and evaluated at 7 and 15 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . a substantial synergistic effect occurred between mbi - 005 and chelated fe , at both concentrations of mbi - 005 . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and atrazine were evaluated on crabgrass at the 1 - 2 leaf stage in a laboratory experiment . ten seedlings in 2 . 5 cm square pots containing plant growth mix were sprayed with two suboptimal rates of mbi - 005 , and 35 % of the atrazine label rate ( 0 . 3 gallons / a ), or a combination thereof , at a volume of 40 gal / a using a cabinet track sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated five times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . a substantial synergistic effect occurred between mbi - 005 and atrazine , at either concentration of mbi - 005 at both 7 and 14 days after treatment . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and three common rice herbicides were evaluated on barnyard grass at the 1 - 2 leaf stage in a laboratory experiment . ten seedlings in 2 . 5 cm square pots containing plant growth mix were sprayed to full coverage using a hand sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated three times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . synergistic effect were noted between mbi - 005 and all three rice herbicides , 14 days after treatment . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and five common rice herbicides were evaluated on small flower umbrella sedge at the 0 . 5 - 1 leaf stage in a laboratory experiment . twenty seedlings in 2 . 5 cm square pots containing plant growth mix were sprayed to full coverage using a hand sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated three times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . synergistic effects were noted 14 days after treatment between mbi - 005 and all three rice herbicides , with clomazone showing the greatest synergism with mbi - 005 . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and the common rice herbicide propanil were evaluated on barnyard grass at the 1 - 2 leaf stage in a laboratory experiment . ten seedlings in 2 . 5 cm square pots containing plant growth mix planting media were sprayed with 12 . 5 % or 25 % of the label rate of mbi - 005 , 25 % of the propanil label rate , or a combination thereof , to full coverage using a hand sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated three times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . synergistic effects were noted between both rates of mbi - 005 and propnail , 14 days after treatment . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . post - emergent synergistic effects of mbi - 005 and the common rice herbicide thiobencarb are evaluated on smallflower umbrella sedge at the 0 . 5 - 1 leaf stage in a laboratory experiment . twenty seedlings in 2 . 5 cm square pots containing plant growth mix were sprayed with 0 . 5 %, 1 % or 2 % of the label rate of mbi - 005 , 25 % of the thiobencarb label rate , or a combination thereof , to full coverage using a hand sprayer . negative controls were sprayed with water . pots were randomly placed in a growth room at 25 ° c . and 50 % rh , and watered as necessary . treatments were replicated three times and evaluated at 7 and 14 days for visual % damage , with 0 % indicating no damage and 100 % indicating plant death . synergistic effects were observed for three of the four thiobencarb + mbi - 005 combinations , 14 days after treatment . synergy was calculated as the ratio of observed ( e ) to expected ( e / ee ) percent control using colby &# 39 ; s formula . although this invention has been described with reference to specific embodiments , the details thereof are not to be construed as limiting , as it is obvious that one can use various equivalents , changes and modifications and still be within the scope of the present invention . various references are cited throughout this specification , each of which is incorporated herein by reference in its entirety . beauséjour , j ., c . goyer , et al . ( 1999 ). “ production of thaxtomin a by streptomyces scabies strains in plant extract containing media .” can j microbiol 45 : 764 - 768 . duke , s . o ., s . r . baerson , et al . ( 2003 ). “ united states department of agriculture - agricultural research service research on natural products for pest management .” pest manag sci 59 : 708 - 717 . duke , s . o ., f . e . dayan , et al . ( 2000 ). “ natural products as sources of herbicides : current status and future trends .” weed research 40 : 99 - 111 . fry , b . a . and r . loxia ( 2002 ). “ thaxtomin a : evidence for a plant cell wall target .” physiological and molecular plant pathology 60 : 1 - 8 . gerwick , b . c ., p . r . graupner , et al . ( 2005 ). methylidene mevalonates and their use as herbicides . u . p . 7393812 : 16 . healy , f . g ., m . j . wach , et al . ( 2000 ). “ the txtab genes of the plant pathogen streptomyces acidiscabies encode a peptidesynthetase required for phytotoxin thaxtomin a prodcution and pathogenicity .” molecular microbiology 38 : 794 - 804 . hiltunen , l . h ., i . laakso , et al . ( 2006 ). “ influence of thaxtomins in different combinations and concentrations on growth of micropropagated potato shoot cultures .” j agric food chem 54 : 3372 - 3379 . hoagland , r . e . ( 2001 ). “ microbial allelochemicals and pathogens as bioherbicidal agents .” weed technology 15 : 835 - 857 . kang , y ., s . semones , et al . ( 2008 ). methods of controlling algae with thaxtomin and thaxtomin compositions . usa , novozymes biologicals , inc . king , r . r ., c . h . lawrence , et al . ( 1992 ). “ chemistry of phytotoxins associated with streptomyces scabies , the causal organism of potato common scab .” j . agric . food chem 40 : 834 - 837 . king , r . r ., c . h . lawrence , et al . ( 1989 ). “ isolation and characterization of phytotoxin associated with streptomyces scabies .” journal of the chemical society , chemical communications 13 : 849 - 850 . king , r . r ., c . h . lawrence , et al . ( 2003 ). “ more chemistry of the thaxtomin phytotoxins .” phytochemistry 64 : 1091 - 1096 . king , r . r ., c . h . lawrence , et al . ( 2001 ). “ herbicidal properties of the thaxtomin group of phytotoxins .” j agric food chem 49 : 2298 - 2301 . loxia , r ., r . a . bukhalid , et al . ( 1995 ). “ differential production of thaxtomins by pathogenic streptomyces species in vitro ” phytopathology 85 : 537 - 541 .
there is a need for a selective , low - risk herbicide that can be used to control weeds in cereal cultures and turf . the present invention discloses that a bacterial secondary metabolite , thaxtomin and optionally another herbicide is an effective herbicide on broadleaved , sedge and grass weeds . thaxtomin a and structurally similar compounds can be used as natural herbicides to control the germination and growth of weeds in cereal , turf grass , timothy grass and pasture grass cultures with no phytotoxicity to these crops . as a natural , non - toxic compound , thaxtomin can be used as a safe alternative for weed control in both conventional and organic farming and gardening systems .