AQUEOUS HERBICIDE CONCENTRATES

Abstract

Herbicide concentrate compositions containing a combination of herbicides are provided; in particular, the present invention relates to aqueous herbicide concentrate compositions containing a particulate encapsulated acetanilide herbicide and a protoporphyrinogen oxidase inhibitor (PPO inhibitor).

Description

FIELD OF INVENTION The present invention relates, in general, to herbicidal concentrate compositions containing a combination of herbicides. In particular, the present invention relates to aqueous herbicidal concentrate compositions containing a particulate encapsulated acetanilide herbicide and a protoporphyrinogen oxidase inhibitor (PPO inhibitor). BACKGROUND OF THE INVENTION The outbreak of certain herbicide-resistant weeds has generated interest in developing strategies to complement the action of primary herbicides such as glyphosate. Acetanilide herbicides are known as effective residual control herbicides that reduce weed competition early in the season. In particular, acetanilide herbicides, such as acetochlor, provide excellent residual control of many grasses and broadleaves, including amaranth, waterhemp, pigweed, nightshade, foxtail, among others. Acetanilides are generally classified as seedling growth inhibitors. Seedling growth inhibitors are taken up and translocated in plants from germination to emergence, primarily through subsurface emerging buds or seedling roots.Acetanilide herbicides typically do not offer significant post-emergence activity, but as residual herbicides, they control small-seeded dicot and newly emerged monocot weed species. This complements the activity of post-emergence herbicides that lack significant residual activity. Crop damage caused by the application of acetanilide herbicides requires strategies to reduce this effect. One strategy involves applying acetanilide herbicide formulations after crop emergence (i.e., postemergence) but before the emergence of later-germinating weeds (i.e., pre-emergence). However, application during this time frame can cause foliar damage to the crop. Other strategies to reduce crop damage include microencapsulation of the acetanilide herbicide. Methods for producing microencapsulated acetanilides are described in various patents and publications, including U.S. Patent No. 5,925,595; U.S. Publication No. 2004 / 0137031; and U.S. Publication No. 2010 / 0248963. Another class of herbicides that exhibits effective residual control and activity against persistent herbicide-resistant weeds such as Palmer amaranth (Amaranthus palmer!) includes protoporphyrinogen oxidase (PPO) inhibitors. PPO inhibitors include herbicides such as acifluorfen, azafenidin, bifenox, butafenacil, carfentrazone-ethyl, flufenpyr-ethyl, flumiclorac, flumiclorac-pentyl, flumioxazin, fluoroglycofen, fluthiacet-methyl, fomesafen, lactofen, oxadiargyl, oxadiazon, oxyfluorfen, pyraflufen-ethyl, saflufenacil, and sulfentrazone, their salts and esters, and mixtures thereof. Herbicidal compositions containing a combination of herbicides with multiple modes of action and that can complement the action of primary herbicides such as glyphosate are especially suitable for controlling the growth of undesired plants, including those with resistance to selected herbicides. Diluted tank mix compositions of encapsulated acetanilide herbicides and PPO inhibitors are known in the art. However, the mixtures are typically prepared at the time of use by the end user. There remains a need for highly concentrated herbicidal compositions containing encapsulated acetanilide herbicides and PPO inhibitors that are convenient for agricultural workers to formulate as spray solutions and that avoid the risk of tank mixing errors. Furthermore, the stability of encapsulated acetanilide herbicide concentrates makes them sensitive to the inclusion of other additives, including co-herbicides. Consequently, there remains a need for highly concentrated herbicidal compositions containing encapsulated acetanilide herbicides and PPO inhibitors that can be produced economically, have sufficient stability, and can be diluted to provide effective spray formulation solutions for application to non-target plants. BRIEF DESCRIPTION OF THE INVENTION In one aspect, the present invention relates to an aqueous herbicidal concentrate composition comprising: microcapsules comprising an acetanilide herbicide, wherein the concentration of the acetanilide herbicide in the composition on an active ingredient basis is at least about 25% by weight; a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor); and at least about 750 ppm of a pseudoplastic thickener based on the total weight of the composition. In another aspect, the present invention relates to an aqueous herbicidal concentrate composition comprising: microcapsules comprising an acetanilide herbicide, wherein the concentration of the acetanilide herbicide in the composition on an active ingredient basis is at least about 25% by weight; a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor); zcconn / i znz / B / v a structure-destroying agent in a concentration of less than about 3.5% by weight; and a density adjusting agent, wherein the total concentration of structure-destroying agent and density adjusting agent is between about 7% by weight and about 10% by weight, between about 7.5% by weight and about 9% by weight, or between about 8% by weight and about 9% by weight. In another aspect, the present invention relates to an aqueous herbicidal concentrate composition comprising: microcapsules comprising an acetanilide herbicide, wherein the concentration of the acetanilide herbicide in the composition on an active ingredient basis is at least about 25% by weight; a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor); at least about 750 ppm of a pseudoplastic thickener based on the total weight of the composition; a structure-destroying agent in a concentration of less than about 3.5% by weight; and a density-adjusting agent, wherein the total concentration of structure-destroying agent and density-adjusting agent is between about 7% by weight and about 10% by weight, between about 7.5% by weight and about 9% by weight, or between about 8% by weight and about 9% by weight. In another aspect, the present invention relates to an aqueous herbicidal concentrate composition comprising: microcapsules comprising a core material comprising an acetanilide herbicide and a shell wall material encapsulating the core material; an aqueous phase comprising the acetanilide herbicide (unencapsulated acetanilide) and a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor), wherein the concentration of total acetanilide herbicide in the composition on an active ingredient basis is at least about 25% by weight; the weight ratio of total acetanilide herbicide to PPO inhibitor is between about 1:10 and 10:1; and the concentration of the acetanilide herbicide in the aqueous phase is between about 0.5% and about 10% of the total weight of the acetanilide herbicide. On the one hand, other objects and characteristics will be evident, and on the other, they will be indicated later. zcconn / i znz / B / v DETAILED DESCRIPTION OF THE INVENTION In general, the present invention relates to aqueous herbicidal concentrate compositions comprising a combination of at least one encapsulated acetanilide herbicide and at least one PPO inhibitor herbicide. One aspect of the present invention is to provide a highly concentrated herbicidal composition containing at least one encapsulated acetanilide herbicide and at least one PPO inhibitor that can be diluted to provide an effective spray formulation solution. A highly concentrated composition reduces the volume of liquid and associated packaging that would otherwise be required for more dilute compositions. The smaller volume reduces the space required to store and transport the concentrated composition prior to sale or use. Furthermore, a highly concentrated herbicidal composition containing an acetanilide herbicide and a PPO inhibitor is convenient for farmworkers to formulate as spray solutions and avoids the risk of tank-mixing errors. Another aspect of the present invention is to provide a highly concentrated herbicidal composition containing an encapsulated acetanilide herbicide and a PPO inhibitor that is stable and does not appreciably phase separate, form precipitates, or form gels upon standing or storage. A stable and compatible highly concentrated herbicidal composition conveniently provides a uniform spray formulation solution upon dilution without the need for excessive agitation. In accordance with the present invention, the concentrate compositions comprise a PPO inhibitor. PPO inhibitors include herbicides such as acifluorfen, azafenidin, bifenox, butafenacil, carfentrazone-ethyl, flufenpyr-ethyl, flumiclorac, flumicloracpentyl, flumioxazin, fluoroglycofen, fluthiacet-methyl, fomesafen, lactofen, oxadiargyl, oxadlazon, oxyfluorfen, pyraflufen-ethyl, saflufenacil, and sulfentrazone, their salts and esters, and mixtures thereof. Some PPO inhibitor herbicides are available in their free forms, as salts, or as derived materials, for example, as esters. In various embodiments, the concentrate compositions comprise a water-soluble PPO inhibitor. In some embodiments, the water-soluble PPO inhibitor is selected from the group consisting of water-soluble salts of fomesafen and acifluorfen.In certain embodiments, the water-soluble PPO inhibitor is selected from the group consisting of fomesafen sodium and acifluorfen sodium. In other embodiments, the water-soluble PPO inhibitor comprises fomesafen sodium. Typically, the aqueous herbicidal concentrate compositions of the present invention contain at least about 2% by weight, at least about 4% by weight, at least about 5% by weight, at least about 6% by weight, or at least about 8% by weight of the PPO inhibitor on an active ingredient basis.In these and other embodiments, the aqueous herbicidal concentrate compositions contain between about 2% by weight and about 20% by weight, between about 4% by weight and about 20% by weight, between about 5% by weight and about 20% by weight, between about 5% by weight and about 15% by weight, between about 5% by weight and about 10% by weight, between about 6% by weight and about 15% by weight, or between about 6% by weight and about 10% by weight of the PPO inhibitor on an active ingredient basis. Concentrated compositions further comprise an encapsulated acetanilide herbicide (e.g., acetanilide herbicide microcapsules). Acetanilide herbicides include herbicides such as acetochlor, alachlor, butachlor, butenachlor, delachlor, diethyl, dimethachlor, mefenacet, metazochlor, metolachlor, S-metolachlor, pretilachlor, propachlor, propisochlor, prinachlor, terbuchlor, thenylchlor, and xylachlor, mixtures thereof, and stereoisomers thereof. Some acetanilide herbicides are available in their free forms, as salts, or as derived materials, e.g., acetanilide herbicide is selected from butachlor, metolachlor, and S-metolachlor. In some embodiments, they are available as esters. In various embodiments, the group consisting of acetochlor, alachlor, certain embodiments, the zcconn / i ζπζ / β / υ acetanilide herbicide is selected from the group consisting of acetochlor, metolachlor, and S-metolachlor. In various embodiments, the acetanilide herbicide comprises acetochlor. The aqueous herbicidal concentrate compositions of the present invention contain at least about 15% by weight, at least about 20% by weight, at least about 25% by weight, at least about 30% by weight, or at least about 35% by weight of the acetanilide herbicide on an active ingredient basis. In these and other embodiments, the aqueous herbicidal concentrate compositions contain between about 15% by weight and about 40% by weight, between about 20% by weight and about 40% by weight, between about 30% by weight and about 35% by weight, or between about 40% by weight. 20% by weight and approximately 35% by weight, between approximately approximately approximately approximately approximately the the the the 20% 25% 25% 30% by by by weight weight weight weight approximately approximately approximately the the the 30% 40% 35% by weight, weight, weight, about 40% by weight or between about 30% by weight and about 35% by weight of the acetanilide herbicide on an active ingredient basis. The weight ratio of total acetanilide herbicide to PPO inhibitor on an acid equivalency (ae) basis may be between about 1:10 and about 10:1, between about 1:8 and about 8:1, between about 1:6 and about 6:1. In various embodiments, the weight of the acetanilide herbicide is greater than the weight of the PPO inhibitor. Therefore, the herbicide weight ratio of zcconn / i znz / B / v Total acetanilide to PPO inhibitor on an acid equivalency basis may be between about 2:1 and about 10:1, between about 2:1 and about 8:1, between about 3:1 and about 10:1, between about 3:1 and about 8:1, between about 4:1 and about 10:1, between about 4:1 and about 8:1, between about 5:1 and about 10:1, or between about 5:1 and about 8:1. In general, at least a portion of the acetanilide herbicide component of the concentrated compositions of the present invention is encapsulated (e.g., in microcapsules). Encapsulated acetanilide herbicides for use in the present invention are prepared by contacting a continuous aqueous phase containing a polyamine component comprising a polyamine source with a discontinuous oil phase containing the acetanilide herbicide and a polyisocyanate component comprising a polyisocyanate source. A polyurea shell wall is formed in a polymerization reaction between the polyamine source and the isocyanate source at the oil / water interface, thereby forming a capsule or microcapsule containing the acetanilide herbicide. Accordingly, microcapsules comprising the acetanilide herbicide may comprise a polyurea shell wall. The polyurea polymer shell wall of the microcapsules can be formed using one or more polyisocyanates, i.e., with two or more isocyanate groups per molecule. In some embodiments, the polyurea shell wall is formed using a mixture of at least two polyisocyanates. For example, the polyurea shell wall is formed in an interfacial polymerization reaction using at least one diisocyanate and at least one triisocyanate. Multiple polyisocyanates can be employed. For example, the polyisocyanate component can comprise an aliphatic polyisocyanate such as those based on hexamethylene diisocyanate (e.g., DESMODUR N 3200 and DESMODUR N 3215). The polyamine source may be a single polyamine species or a mixture of two or more different polyamine species. In some embodiments of the present invention, the polyamine source consists essentially of a parent polyamine. As used herein, a parent polyamine refers to a polyamine consisting essentially of a single polyamine species. The polyisocyanate source may also be a single polyisocyanate species or a mixture of two or more different polyisocyanate species. See, e.g., U.S. Pat. No. 5,925,595; U.S. Publication No. 2004 / 0137031; and US Publication No. 2010 / 0248963, which are incorporated herein by this reference. In general, an aqueous dispersion of acetanilide capsules or microcapsules can be produced by an interfacial polymerization reaction, either continuously or batchwise, using means known in the art. However, preferably, a polyamine is polymerized with one or more polyisocyanates at the interface of an oil-in-water emulsion. The discontinuous oil phase (also referred to herein as the internal phase) preferably comprises one or more polyisocyanates, and a continuous aqueous phase (also referred to herein as the external phase) comprises the principal amine. The oil phase further comprises a core material comprising an acetanilide herbicide as the active ingredient. An oil-in-water emulsion is preferably formed by adding the oil phase to a continuous aqueous phase to which an emulsifying or dispersing agent has been added (e.g., pre-dissolved therein). The emulsifying agent is selected to achieve the desired oil droplet size in the emulsion. The oil droplet size in the emulsion is determined by several factors in addition to the emulsifying agent used and determines the size of the microcapsules formed by the process. The emulsifying agent is preferably a protective colloid. Polymeric dispersants are preferred as protective colloids. Polymeric dispersants provide steric stabilization to an emulsion by adsorbing an oil droplet to the surface and forming a high-viscosity layer that prevents droplet coalescence.Polymeric dispersants can be surfactants and are preferred over non-polymeric surfactants because polymeric compounds form a stronger interfacial film around the oil droplets. If the protective colloid is ionic, the layer formed around each oil droplet will also serve to electrostatically prevent the droplets from coalescing. SOKALAN (marketed by BASF), a copolymer of olefin and maleic acid, is a preferred protective colloid, as are INVALON (marketed by Huntsman) and AGNIQUE NSC 11NP (marketed by BASF), which are naphthalene sulfonate condensates. Other protective colloids useful in the present invention are gelatin, casein, polyvinyl alcohol, alkylated polyvinylpyrrolidone polymers, maleic anhydride and methyl vinyl ether copolymers, styrene and maleic anhydride copolymers, maleic acid-butadiene and diisobutylene copolymers, sodium and calcium lignosulfonates, condensed naphthalene formaldehyde sulfonate, modified starches and modified cellulose products such as hydroxyethylcellulose or hydroxypropylcellulose and carboxymethylcellulose. It is convenient to select a polyamine component and a polyisocyanate component such that the polyamine has an amino functionality of at least 2, i.e., 3, 4, 5 or more, and at least one of the polyisocyanates has an isocyanate functionality of at least 2, i.e., 2.5, 3, 4, 5 or more, since high amino and isocyanate functionality increases the percentage of crosslinking between the individual polyurea polymers comprising the shell wall. In some embodiments, the polyamine has an amino functionality greater than 2 and the polyisocyanate is a mixture of polyisocyanates wherein each polyisocyanate has an isocyanate functionality greater than 2. In other embodiments, the polyamine comprises a trifunctional polyamine and the polyisocyanate component comprises one or more trifunctional polyisocyanates.In other embodiments, the shell wall is formed by the reaction between a polyisocyanate or a mixture of polyisocyanates having an average of at least 2.5 reactive groups per molecule and a polyamine having an average of at least three reactive groups per molecule. It is also advantageous to select concentrations of the polyamine component and the polyisocyanate component such that the polyisocyanate component reacts substantially completely to form the polyurea polymer. Complete reaction of the polyisocyanate component increases the percentage of crosslinking between the polyurea polymers formed in the reaction, thereby providing structural stability to the shell wall.These factors, i.e., the ratio of the weight of the core material components to the weight of the shell wall components, the average particle sizes of the herbicide microcapsules, the degree of crosslinking, among other factors, can be selected to affect the release rate profile of the herbicide microcapsule population, thus allowing the preparation of herbicide microcapsules that balance enhanced crop safety while still being effective for weed control. Microencapsulated acetanilide can be prepared by the methods described in U.S. Publication No. 2010 / 0248963. In particular, the method includes encapsulating the core material comprising the acetanilide herbicide in a shell wall formed by reacting a polyamine component and a polyisocyanate component in a reaction medium at concentrations such that the reaction medium comprises an excess of molar equivalents of amino groups as compared to isocyanate groups. That is, the molar equivalent ratio of amine equivalents to isocyanate equivalents used in preparing the shell wall of the microcapsules is greater than 1:1. For example, a molar equivalent ratio of at least 1.01:1, or at least about 1.05:1, is used to ensure that the isocyanate is fully reacted.The ratio of molar equivalents of amine contained in the polyamine component to the molar equivalents of isocyanate contained in the polyisocyanate component may be between 1.01:1 and zcconn / i ζπζ / β / υ. about 1.7:1, between 1.01:1 and about 1.6:1, between 1.01:1 and about 1.5:1, between 1.01:1 and about 1.4:1, between 1.01:1 and about 1.3:1, between 1.05:1 and about 1.7:1, between 1.05:1 and about 1.6:1; between 1.05:1 and about 1.5:1; between 1.05:1 and zcconn / i ζπζ / β / υ approximately 1.4:1 or between 1.05:1 and approximately 1.3:1. The ratio of molar equivalents of amine to molar equivalents of isocyanate is calculated according to the following equation: Molar equivalent ratio = amine molar equivalents (1) isocyanate molar equivalents In the above equation (1), the molar equivalents of amine are calculated according to the following equation: molar equivalents = Z(polyamine weight / equivalent weight). In the above equation (1), the molar equivalents of isocyanate are calculated according to the following equation: molar equivalents of isocyanate = Z(weight of polyisocyanate / equivalent weight). The equivalent weight is usually calculated by dividing the molecular weight in grams / mol by the number of functional groups per molecule. For some molecules, e.g., triethylenetetramine (TETA) and 4,4'-diisocyanato-dicyclohexylmethane (DES W), the equivalent weight is equal to the molecular weight divided by the number of functional groups per molecule. For example, TETA has a molecular weight of 146.23 g / mol and 4 amino groups. Thus, the equivalent weight is 36.6 g / mol. This calculation is usually correct, but for some materials, the actual equivalent weight may vary from the calculated equivalent weight. For some components, e.g., the biuret-containing (i.e., trimer) adduct of hexamethylene-1,6-diisocyanate, the equivalent weight of the commercially available material differs from the theoretical equivalent weight due to, for example, incomplete reaction.The theoretical equivalent weight of the biuret-containing adduct (i.e., trimer) of hexamethylene-1,6-diisocyanate is 159.5 g / mol. The actual equivalent weight of hexamethylene-1,6-diisocyanate trimer (DES N3200), the commercially available product, is approximately 183 g / mol. In the above calculations, this actual equivalent weight is used. The actual equivalent weight can be obtained from the manufacturer or by titration with a suitable reagent via methods known in the art. The symbol Σ in the amine molar equivalents calculation means that the amine molar equivalents comprise the sum of the amine molar equivalents for all polyamines in the reaction medium. Likewise, the symbol Σ in the isocyanate molar equivalents calculation means that the isocyanate molar equivalents comprise the sum of the isocyanate molar equivalents for all polyisocyanates in the reaction medium. As stated in U.S. Publication No. 22010 / 0248963, it is believed, without being bound by any particular theory, that the combination of increased particle size and coating characteristics resulting from a large excess of unreacted amino groups significantly reduce the release rate, which is the amount of herbicide to which the crop plants are exposed after application, thereby providing improved crop safety and reduced crop plant injury. It is believed, without being bound by any particular theory, that the increased excess of amino groups produces a significant amount of unreacted amino functional groups, thereby providing a coating having a high amount of amino functional groups that are not crosslinked.The resulting shell wall is believed to be flexible and resistant to rupture, so that the amount of herbicide to which crop plants are initially exposed after application of a herbicide formulation containing the microcapsules is reduced. It is also believed that the unreacted amino groups may reduce the number of fissures or cracks in the shell wall, thereby reducing leakage and herbicide flow through the core shell wall. Accordingly, in various embodiments, the molar concentration of amino groups of the polyamine component and the molar concentration of isocyanate groups of the polyisocyanate(s) (i.e., a polyisocyanate, a mixture of two polyisocyanates, a mixture of three polyisocyanates, etc.) in the reaction medium is such that the ratio of the concentration of amine molar equivalents to the concentration of isocyanate molar equivalents is at least about 1.1:1. In various embodiments, the molar equivalent ratio of amine molar equivalents to isocyanate molar equivalents can be at least about 1.15:1 or even at least about 1.20:1. In some embodiments, the molar equivalent ratio is less than about 1.7:1, less than about 1.6:1, less than about 1.5:1, less than about 1.4:1, or even less than about 1.3:1.In various embodiments, the molar equivalent ratio of amine molar equivalents to isocyanate molar equivalents in the polymerization medium is between 1.1:1 and about 1.7:1, between 1.1:1 and about 1.6:1, between 1.1:1 and about 1.5:1, between 1.1:1 and about 1.4:1, between 1.1:1 and about 1.3:1, between about 1.15:1 and about 1.7:1, between about 1.15:1 and about 1.6:1, between about 1.15:1 and about 1.5:1, between about 1.15:1 and about 1.4:1, between about 1.15:1 and about 1.3:1, between 1.2:1 and about 1.7:1, between 1.2:1 and about 1.6:1, between 1.2:1 and zcconn / i znz / B / v about 1.5:1, between 1.2:1 and about 1.4:1 or between 1.2:1 and about 1.3:1. Some examples of typical ratios include 1.1:1, 1.15:1, 1.2:1, 1.25:1, 1.3:1, 1.35:1, 1.4:1, 1.45:1 and 1.5:1. In general, microcapsules can be characterized as having an average particle size of at least about 2, 3, 4, 5, 6, 7, 8, 9, or 10 pm. For example, microcapsules have an average particle size range of between about 2 pm and about 15 pm, between about 2 pm and about 12 pm, or between about 6 pm and about 15 pm. The capsules or microcapsules are essentially spherical such that the average cross-sectional dimension defined by any point on one surface of the microcapsule to a point on the opposite side of the microcapsule is essentially the diameter of the microcapsule. The average particle size of the microcapsules can be determined by measuring the particle size of a representative sample with a laser light scattering particle size analyzer known to those skilled in the art.An example of a particle size analyzer is a Coulter LS particle size analyzer. Furthermore, according to the methods described in U.S. Publication No. 22010 / 0248963, encapsulated acetanilides can be prepared wherein the particles (i.e., capsules or microcapsules) are characterized by having an average particle size of at least about 7 pm. The microencapsulated acetanilide particles can be characterized by having an average particle size of at least about 8 pm, at least about 9 pm, or at least about 10 pm. In various embodiments, the encapsulated acetanilide particles are characterized by having an average particle size of less than about 15 pm or less than 12 pm.Thus, the microencapsulated acetanilide may be characterized as having an average particle size of between about 7 pm and about 15 pm, between about 7 pm and about 12 pm, between about 8 pm and about 12 pm, or between about 9 pm and about 12 pm. In particularly preferred embodiments, the range is between about 9 pm and about 11 pm. In certain embodiments, the core material may further comprise one or more release compounds (e.g., an acetanilide and one or more additives compatible therewith that act to enhance its bioefficacy on weeds or reduce crop damage). For example, in some embodiments, the core material optionally comprises a safener. Suitable safeners include, for example, furilazole ((RS)-3-(dichloroacetyl)-5-(2-furanyl)-2,2-dimethyl-1,3-oxazolidine 95%), available from Monsanto Company; AD 67 (4-(dichloroacetyl)-1-oxa-4-azaspiro[4,5]decane); benoxacor (CGA 154281, zcconn / i znz / B / v (RS)-4-dichloroacetyl-3,4-dihydro-3-methyl-2H-1,4-benzoxazine); cloquintocet-mexil (CGA 184927, (5-chloroquinolin-8-ilox¡)acetic acid); cyometrinyl (CGA 43089, (Z)cyanomethoxymino(phenyl)acetonítrile); cyprosulfamide (N-[4-(cyclopropylcarbamoyl)phenylsulfonyl]-oanisamide); dichlormid (DDCA, R25788, N,N-diallyl-2,2-dichloroacetanilide);diciclonon ((RS)-1dicloroacetyl-3,3,8a-trimetilper¡drop¡rrolo[1,2-a]p¡rim¡d¡n-6-ona); dietolato (0,0-dietil O-fenil fosforotioato) fenclorazol-etilo (HOE 70542, ácido 1-(2,4-diclorofenil)-5-triclorometil-1 H-1,2,4triazol-3-carboxílico); fenclorim (CGA 123407 4, 6-dicloro-2-fen¡lp¡r¡mid¡na); flurazol (bencil 2cloro-4-trifluorometil-1,3-tiazol-5-carboxilato); fluxofenim (CGA 133205, 4'-chloro-2,2,2trifluoroacetophenona (EZ)-O-1,3-dioxolan-2-¡lmet¡lox¡ma); isoxadifen (acido 4,5-dihidro-5,5dif en i I-1,2-oxazol-3-carboxylo); mefenpir (acido (RS)-1 - (2,4-diclo rof en il)-5-metí I-2-pi razol in n3,5-dicarboxylico); mefenato (4-chlorophenyl methylcarbamato); MG 191; anhydrido naftálico; oxabetrinil (CGA 92194 y(Z)-1,3-d·oxolan-2-ilmetox·m·no(fen·l)aceton·tr·lo).; In general, the encapsulated acetanilide herbicide particles comprise a core material containing a water-immiscible agricultural chemical encapsulated in a polyurea shell wall, which is preferably substantially non-microporous, such that release of the core material occurs through a molecular diffusion mechanism rather than a flow mechanism through a pore or crevice in the polyurea shell wall. As indicated herein, the shell wall may preferably comprise a polyurea product of a polymerization of one or more polyisocyanates and a principal polyamine (and an optional auxiliary polyamine). Typically, the encapsulated acetanilide herbicide particles (e.g., capsules or microcapsules) are dispersed in a liquid medium, preferably water.The acetanilide herbicide loading of the encapsulated acetanilide herbicide dispersion is typically between about 5% and about 50% by weight considering the active ingredients, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or even 50% by weight considering the active ingredients. The aqueous herbicidal concentrate is prepared by combining the aqueous dispersion of encapsulated acetanilide herbicide particles and the PPG inhibitor component. The water-soluble PPO inhibitor component can be prepared by adding the acidic herbicide (e.g., fomesafen) to water and then adding a suitable base (e.g., sodium hydroxide) with stirring to prepare a solution of the water-soluble PPO inhibitor salt. The resulting solution is mixed with the encapsulated acetanilide herbicide dispersion to form the aqueous herbicidal concentrate composition. The encapsulated acetanilide herbicide dispersion and aqueous herbicidal concentrate compositions of the present invention may contain one or more additives. For example, in various embodiments, the acetanilide herbicide dispersion and / or aqueous herbicidal concentrate compositions comprise one or more of the following additives: dispersant(s), surfactant(s), thickener(s), structure-breaking agent(s), density adjusting agent(s), antifreeze agent(s), anticaking agent(s), drift control agent(s), preservative(s), and antifoam agent(s). In various aspects, the encapsulated acetanilide herbicide dispersion and, consequently, the aqueous herbicidal concentrate compositions of the present invention comprise one or more thickeners. In general, thickeners are useful for retarding the settling process by increasing the viscosity of the aqueous phase. In various embodiments, shear thinning thickeners (i.e., shear thinning thickeners) are preferred because they reduce the viscosity of the dispersion during pumping, which facilitates economical application and uniform coverage of the dispersion to an agricultural field using equipment commonly used for such purposes. Some examples of useful shear thinning thickeners include water-soluble guar- or xanthan-based gums (e.g., Kelzan ex. CPKelco), cellulose ethers (e.g., ETHOCEL ex. Dow), and modified cellulose polymers and products (e.g., Aqualon thickeners ex. Hercules).In some embodiments, the pseudoplastic thickener comprises a water-soluble gum selected from the group consisting of guar gum, xanthan gum, and a combination thereof. In certain embodiments, the pseudoplastic thickener comprises xanthan gum. Some encapsulated acetanilide herbicide dispersions known in the art contain less than about 500 ppm or about 600 ppm of thickener. Beyond this concentration range, the viscosity of the dispersion increases to a point that can result in poor pumpability and possible gelation of the encapsulated acetanilide herbicide particles. Contrary to this belief, however, it has surprisingly been discovered that when an aqueous herbicidal concentrate is formulated containing an encapsulated acetanilide herbicide (e.g., microcapsules) and a PPO inhibitor (e.g., water-soluble PPO), the thickener concentration exceeds this critical maximum by a significant amount in order to provide a stable composition (i.e., a composition with a sufficiently high viscosity, without significant phase separation).Accordingly, in various embodiments, the aqueous herbicidal concentrate compositions comprise at least about 750 ppm, at least about 800 ppm, at least about 850 ppm, at least about 900 ppm, or at least about 950 ppm of a thickener (e.g., a shear-like thickener) based on the total weight of the composition. Generally, the concentration of the thickener is less than about 2000 ppm, less than about 1800 ppm, less than about 1500 ppm, less than about 1300 ppm, or less than about 1200 ppm. In some embodiments, the concentration of the thickener is between about 800 ppm and about 1500 ppm or between about 900 ppm and about 1200 ppm. In certain embodiments, after formulation, the viscosity of the encapsulated acetanilide herbicide dispersion may preferably range from about 100 cps to about 600 cps, as tested with a Haake Rotovisco viscometer and measured at about 102 C using a spindle rotating at about 45 rpm. More preferably, the viscosity may range from about 100 cps to about 300 cps. Dispersants are useful for inhibiting agglomeration and settling of the microcapsules and are present during the interfacial polymerization reaction used in the preparation of the acetanilide microcapsules. Accordingly, in various embodiments, the encapsulated acetanilide herbicide dispersion and, consequently, the aqueous herbicidal concentrate compositions of the present invention comprise one or more dispersants. It is possible that low molecular weight dispersants solubilize the walls of the acetanilide capsule or microcapsule shells, especially in the initial stages of their formation, causing difficulties in gelation. Thus, in some embodiments, the dispersants have relatively high molecular weights of at least about 1.5 kg / mol, more preferably at least about 3 kg / mol, and even more preferably at least about 5, 10, or even 15 kg / mol.In some embodiments, the molecular weight can range from about 5 kg / mol to about 50 kg / mol. Dispersants can also be nonionic or anionic. An example of a high molecular weight anionic polymeric dispersant is the sodium salt of polymeric naphthalene sulfonate such as Invalon (formerly Irgasol, Huntsman Chemicals). Other useful dispersants mentioned above include gelatin, casein, ammonium caseinate, polyvinyl alcohol, alkylated polyvinylpyrrolidone polymers, maleic anhydride-methyl vinyl ether copolymers, styrene-maleic anhydride copolymers, maleic acid-butadiene-diisobutylene copolymers, sodium and calcium lignosulfonates, naphthalene formaldehyde condenser, modified starches and modified cellulose products such as hydroxyethylcellulose or hydroxypropylcellulose and sodium carboxymethylcellulose. It has been discovered that adjusting the dispersant concentration is important in achieving a stable concentrate. Surprisingly, it has been observed that when a stable dispersion of encapsulated acetanilide herbicide is mixed with an aqueous PPO inhibitor concentrate, the resulting mixture is unstable and phase separation occurs. Therefore, simply mixing commercially available encapsulated acetanilide concentrates and PPO inhibitor concentrates is not expected to provide stable concentrate mixtures. Some stable formulations of encapsulated acetanilide herbicides are known to contain about 3% by weight of total dispersant. Instead, in accordance with the invention, to provide stable aqueous herbicidal concentrate compositions, the total dispersant concentration is increased to at least about 3.5% by weight or to at least about 3.75% by weight (e.g.,, between about 3.5% by weight and about 5% by weight or between about 3.75% by weight and about 4.5% by weight). To improve storage stability and prevent gelation of the aqueous encapsulated acetanilide herbicide particles, particularly upon storage in high temperature environments, the liquid dispersions and, consequently, the aqueous herbicidal concentrate compositions preferably include a structure-breaking agent. Gelation is a major concern for some encapsulated acetanilide herbicide dispersions because the process is difficult, if not impossible, to reverse and can result in a product unsuitable for dilution and application. Accordingly, in various embodiments, the encapsulated acetanilide herbicide dispersion and, consequently, the aqueous herbicidal concentrate compositions of the present invention comprise one or more structure-breaking agents. A preferred structure-breaking agent is urea.To prevent gelation, in some embodiments, the concentrated compositions include at least about 4, 5, or 6% by weight and up to about 20% by weight or up to about 10% by weight (e.g., between about 4% by weight and about 10% by weight) of the structure-killing agent. However, in some embodiments, it has been surprisingly discovered that when certain aqueous herbicidal concentrates of the present invention are formulated containing encapsulated acetanilide herbicide (e.g., microcapsules) and a PPO inhibitor (e.g., water-soluble PPO), the concentration of the structure-killing agent does not exceed about 3.5% by weight. Typically, at least about 1% by weight, at least about 2% by weight, or at least about 2.5% by weight of the structure-killing agent is necessary in these and other embodiments. Adjusting the density of the aqueous phase to approximate the average weight by volume of the microcapsules also slows the settling process. In addition to its primary purpose, many additives can increase the density of the aqueous phase. A further increase can be achieved by adding density adjusting agents such as sodium chloride and glycols. A preferred density adjusting agent is glycerin. The aqueous herbicidal concentrate compositions can have a density adjusting agent concentration of between about 4% by weight, but not exceeding about 10% by weight. In various embodiments, the density adjusting agent concentration is between about 5% by weight and about 10% by weight, between about 5% by weight and about 8% by weight, between about 5% by weight and about 6.5% by weight, between about 5.5% by weight and about 7% by weight, or between about 5.5% by weight and about 6.5% by weight. In addition to its structure-destroying properties, urea also functions as a density-adjusting agent. In embodiments in which urea is included as a structure-destroying agent, the total concentration of urea and the non-urea density-adjusting agent (e.g., glycerin) is between about 6% and about 10% by weight, between about 6.5% by weight and about 10% by weight, between about 7% by weight and about 10% by weight, between about 7.5% by weight and about 9% by weight, or between about 8% by weight and about 9% by weight. In these embodiments, it has been discovered that this combination of urea and density-adjusting agent (e.g.,, glycerin) provides a stable aqueous herbicidal concentrate composition that is resistant to gelling and settling upon storage, although the concentrations of these components are generally lower than what is typically required to prepare a stable dispersion of encapsulated acetanilide herbicide. In some cases, the weight-to-volume ratio of the encapsulated acetanilide herbicide particles of preferred dimensions is approximated by the density of the core material, where the density of the core material is between about 1.05 and about 1.5 g / cm3. Accordingly, in various embodiments, the density of the aqueous phase of the concentrate is formulated to be within about 0.2 g / cm3 of the average weight-to-volume ratio of the encapsulated acetanilide herbicide particles. Surfactants may optionally be included in the aqueous herbicidal concentrate composition. Suitable surfactants are selected from nonionic, cationic, anionic surfactants, and mixtures thereof. Examples of suitable surfactants for the practice of the present invention include, but are not limited to: alkoxylated tertiary etheramines (e.g., TOMAH E-series surfactants); alkoxylated quaternary etheramines (e.g., TOMAH Q-series surfactant); alkoxylated etheramine oxides (e.g., Zcconn / i Znz / B / v surfactant TOMAH AO series); alkoxylated tertiary amine oxides (e.g., AROMOX series surfactants); alkoxylated tertiary amine surfactants (e.g., ETHOMEEN T and C series surfactants); alkoxylated quaternary amines (e.g., ETHOQUAD T and C series surfactants); alkyl sulfates, alkyl ether sulfates, and alkyl aryl ether sulfates (e.g., WITCOLATE series surfactants); alkyl sulfonates, alkyl ether sultanates, and alkyl aryl ether sultanates (e.g., WITCONATE series surfactants); alkoxylated phosphate esters and diesters (e.g., PHOSPHOLAN series surfactants); alkyl polysaccharides (e.g., AGRIMUL PG series surfactants); alkoxylated alcohols (e.g., BRIJ or HETOXOL series surfactants); and mixtures thereof. Anti-caking agents facilitate redispersion of encapsulated acetanilide herbicide particles (e.g., microcapsules) upon agitation of a formulation in which the particles have settled. A microcrystalline cellulose material such as FMC's Lattice is effective as an anticaking agent. Other suitable anticaking agents include, for example, clay, silicon dioxide, insoluble starch particles, and insoluble metal oxides (e.g., aluminum oxide or iron oxide). Anti-caking agents that change the pH of the dispersion are preferably avoided, at least in some embodiments. The pH of the aqueous herbicidal concentrate composition may range from about 7 to about 9 to reduce eye irritation to persons who may come into contact with the composition during handling or application to crops. However, if the components of a formulated dispersion are pH-sensitive, buffers such as disodium phosphate may be used to maintain the pH within a range within which the components are most effective. In addition, a pH buffer such as citric acid monohydrate may be particularly useful in some systems during the preparation of the encapsulated acetanilide herbicide to enhance the effectiveness of a protective colloid such as SOKALAN CP9. Other useful additives include, for example, biocides or preservatives (e.g., PROXEL, marketed by Avecia), antifreeze agents and antifoam agents (such as Antifoam SE23 marketed by Wacker Silicones Corp. or AGNIQUE DFM-111S marketed by BASF). The aqueous herbicidal concentrate compositions of the present invention may comprise a combination of additives. For example, in various embodiments, the aqueous herbicidal concentrate compositions comprise a combination of additives including a sheath thickener (e.g., xanthan gum), urea, glycerin, and a combination of dispersants (e.g., a naphthalene sultanate condensate, an olefin-maleic acid copolymer, and ammonium caseinate). In certain embodiments, the aqueous herbicidal concentrate compositions comprise a combination of additives including those listed in the following table with approximate concentration ranges: zcconn / i znz / B / v Ingredient Concentration Range Pseudoplastic thickener (e.g., xanthan gum) 800-1500 ppm Urea 2-3.5% by weight Glycerin 5.5-7% by weight Naphthalene sultanate condensate (e.g., INVALON DAM), 3.75-4.5% by weight (Total combined concentration) Olefin and maleic acid copolymer (e.g., SOKALAN CP9), ammonium caseinate In preparing an aqueous herbicidal concentrate composition comprising one or more of the additives mentioned herein, the entire portion of the additive (e.g., thickener, dispersant, structure-breaking agent, density-adjusting agent, etc.) can be added to the liquid dispersion of encapsulated acetanilide herbicide prior to being combined with the PPO inhibitor component. Alternatively, a first portion of the additive can be added during preparation of a stable liquid dispersion of encapsulated acetanilide herbicide, and a second portion can be added during preparation of the aqueous herbicidal concentrate composition (i.e., the mixture of the encapsulated acetanilide herbicide dispersion and PPO inhibitor or solution thereof). In accordance with the present invention, it has been observed that the readily extractable acetanilide herbicide in the aqueous phase of the concentrate compositions can be between about 0.5% and about 10%, between about 0.5% and about 5%, between about 0.5% and about 2%, between about 0.75% and about 10%, between about 0.75% and about 5%, between about 0.75% and about 2%, between about 1% and about 10%, between about 1% and about 5%, or between about 1% and about 2% by weight of the total acetanilide herbicide. Typically, the concentration of the readily extractable acetanilide herbicide in microencapsulated concentrates is much less than 0.5% by weight of the total acetanilide herbicide.Without being bound by any particular theory, it is believed that the PPO inhibitor present in the aqueous phase increases the solubility of the acetanilide herbicide (see Example 7) and produces a higher concentration of readily extractable acetanilide herbicide. The readily extractable acetanilide can be determined by extracting the concentrated composition with a weak solvent such as an aliphatic hydrocarbon solvent and analyzing the extract. Notably, crop safety and weed control efficacy have been found not to be adversely affected by this unexpected result. Accordingly, another aspect of the present invention relates to an aqueous herbicidal concentrate composition comprising microcapsules comprising a core material comprising an acetanilide herbicide and a shell wall material encapsulating the core material; an aqueous phase comprising the acetanilide herbicide (unencapsulated acetanilide) and a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor), wherein the concentration of total acetanilide herbicide is at least about 25% by weight and the concentration of the acetanilide herbicide in the aqueous phase is between about 0.5% and about 10%, between about 0.5% and about 5%, between about 0.5% and about 2%, between about 0.75% and about 10%, between about 0.75% and about 5%, between about 0.75% to about 2%, between about 1% and about 10%, between about 1% and about 5%, or between about 1% and about 2% by weight of the total acetanilide herbicide. As indicated, the weight ratio of total acetanilide herbicide to PPO inhibitor on an acid equivalency (ae) basis can be between about 1:10 and about 10:1, between about 1:8 and about 8:1, between about 1:6 and about 6:1. In various embodiments, the weight of the acetanilide herbicide is greater than the weight of the PPO inhibitor. Therefore, the weight ratio of total acetanilide herbicide to PPO inhibitor on an acid equivalency basis can be between. about 2:1 to about 10:1, between about 2:1 and about 8:1, between about 3:1 and about 10:1, between about 3:1 and about 8:1, between about 4:1 and about 10:1, between about 4:1 and about 8:1, between about 5:1 to about 8:1 and about 10:1, or between about 5:1 and The aqueous herbicidal concentrates described herein are useful; as controlled-release herbicides. Therefore, the present invention also relates to a method for applying an application mixture, which is a dilution of the concentrated composition to control plant growth. The loading of acetanilide herbicide in the application mixture is typically less than about 5% by weight or between about 0.1% and about 5% by weight considering the active ingredients, for example 5%, 4%, 3%, 2%, 1%, 0.5% or 0.1% by weight considering the active ingredients. The application mixture can be applied to a field according to practices known to those skilled in the art. In some embodiments, the application mixture is applied to the soil before or after planting the crop plants, but before the crop plants emerge. Because the release characteristics of the encapsulated acetanilide herbicide particles are adjustable, the timing of the onset of release (or enhanced release) can be controlled, thereby achieving commercially acceptable weed control and a commercially acceptable rate of crop injury. The effective amount of encapsulated acetanilide herbicide and PPO inhibitor to be applied to an agricultural field depends on the identity of the herbicides, the release rate from the capsules or microcapsules, the crop to be treated, and environmental conditions, especially soil type and moisture. Generally, application rates for acetanilide herbicides, e.g., acetochlor, are approximately 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 kilograms of herbicide per hectare, or ranges thereof, e.g., 0.5 to 10 kilograms per hectare, 0.5 to 10 kilograms per hectare, 0.5 to 5 kilograms per hectare, or 1 to 5 kilograms per hectare. In some embodiments, an application rate of about 0.85 to about 1 kilogram per hectare is preferred for sorghum, rice, and wheat. Generally, the application rates of PPO inhibitor herbicides, for example, fomesafen sodium, are approximately 0.05, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4 or 5 kilograms of herbicide per hectare, or their ranges, for example between 0.1 and 5 kilograms per hectare, between 0.5 and 2.5 kilograms per hectare or between 0.5 and 2 kilograms per hectare. Application mixtures of aqueous herbicidal concentrates are preferably applied to an agricultural field within a selected time frame of crop plant development. In various embodiments of the present invention, the application mixture prepared from an aqueous herbicidal concentrate is applied to crop plants post-emergence. For the purposes of the present invention, post-emergence to crop plants includes initial emergence from the soil, i.e., at cracking. In some embodiments, the application mixture is applied to a field between 1 and 40 days prior to crop planting or pre-emergence (i.e., from crop planting until, but not including, emergence or cracking) to achieve control of small-seeded dicot and newly emerged monocot species without significant crop damage.In various embodiments, the application mixture prepared from an aqueous herbicidal concentrate of the present invention is applied pre-emergence to weeds. zcconn / i znz / B / v The application mixtures of the aqueous herbicidal concentrates of the present invention are useful for controlling a wide variety of weeds, i.e., plants that are considered a nuisance or competitor to commercially important crop plants, such as corn, soybeans, cotton, dry beans, snap beans, potatoes, etc. In some embodiments, the application mixtures are applied prior to emergence of the weeds (i.e., pre-emergence application).Examples of weeds that can be controlled according to the method of the present invention include, but are not limited to, foxtail (Alopecurus pratensis) and other weed species of the genus Alopecurus, common Japanese millet (Echinochloa crus-galli) and other weed species of the genus Echinochloa, buffalo grass of the genus Digitada, white clover (Trifolium repens), cottony milkweed (Chenopodium berlandieri), common amaranth (Amaranthus retroflexus) and other weed species of the genus Amaranthus, purslane (Portulaca oleracea) and other weed species of the genus Portulaca, Chenopodium album and other Chenopodium spp., Setaria lutescens and other Setaria spp., Solanum nigrum and other Solanum spp., Lolium multiflorum and other Lolium spp., Brachiaria platyphylla and other Brachiaria spp., Sorghum halepense and other Sorghum spp., Conyza Canadensis and other Conyza spp. and Eleusine indica.In some embodiments, the weeds comprise one or more glyphosate-resistant species, 2,4-D-resistant species, dicamba-resistant species, or ALS-inhibiting herbicide-resistant species. In some embodiments, the glyphosate-resistant weed species are selected from the group consisting of Amaranthus palmeri, Amaranthus rudis, Ambrosia artemisiifolia, Ambrosia trifida, Conyza bonariensis, Conyza canadensis, Digitaria insularis, Echinochloa colona, ​​Eleusine indica, Euphorbia heterophylla, Lolium multiflorum, Lolium rigidum, Plantago lancelata, Sorghum halepense, and Urochloa panicoides. Certain crop plants, such as soybeans and cotton, are less susceptible to the action of acetanilide herbicides and PPO inhibitors than weeds. In accordance with the present invention and based on experimental testing to date, it is believed that the controlled release rate of acetanilide from the encapsulated acetanilide herbicides, in combination with crop plants having lower susceptibility to acetanilide, allows for commercial weed control and commercially acceptable rates of crop injury when the encapsulated acetanilide herbicides are applied to a field either pre-planting or pre-emergence.This allows the use of seedling growth inhibitory acetanilide herbicides or, optionally, seedling growth inhibitory acetanilide herbicides in combination with a PPO inhibitor, in pre-sowing and pre-emergence applications of crop plants. In some embodiments of the present invention, the crop plants include, for example, corn, soybeans, cotton, dry beans, snap beans, and potatoes. The zcconn / i znz / B / v crop plants include hybrid, inbred, and transgenic or genetically modified plants having specific traits or combinations of traits including, but not limited to, herbicide tolerance (e.g., resistance to glyphosate, glufosinate, dicamba, sethoxydim, PPO inhibitor, etc.), Bacillus thuringiensis (Bt), high oil content, high lysine content, high starch content, nutrient density, and drought resistance. In some embodiments, the crop plants are tolerant to organophosphate herbicides, acetolactate synthase (ALS) or acetohydroxyacid synthase (AHAS) inhibitor herbicides, synthetic auxin herbicides, or acetyl-CoA carboxylase (ACCase) inhibitor herbicides.In other embodiments, the crop plants are tolerant to glyphosate, dicamba, 2,4-D, MCPA, quizalofop, glufosinate, or diclofop methyl. In other embodiments, the crop plants are tolerant to glyphosate or dicamba. In some embodiments of the present invention, the crop plants are tolerant to glyphosate or glufosinate. In other embodiments, the crop plants are tolerant to glyphosate, glufosinate, and dicamba. In these and other embodiments, the crop plants are tolerant to PPO inhibitors. Particularly preferred crop species are cotton and soybean. In embodiments where the crop is cotton, it is preferable to apply the application mixture between planting and before crop emergence, before crop planting (e.g., 1-4 weeks before crop planting), and / or after crop emergence (e.g., using a shielded sprayer to keep the application mixture away from the crop). In embodiments where the crop is soybean, it is preferable to apply the application mixture between planting and before crop emergence, before crop planting (e.g., 1-4 weeks before crop planting), and / or after crop emergence. EXAMPLES The following non-limiting examples are provided to further illustrate the present invention. EXAMPLE 1 An aqueous herbicidal concentrate composition was prepared according to the protocol described in this example. A dispersion of microencapsulated acetochlor was prepared as follows. The internal phase was prepared with the components and quantities shown in Table 1-1. The percentages indicate the approximate weight percentage of each component in the final aqueous herbicidal concentrate composition. zcconn / i ζπζ / β / υ TABLE 1-1 zcconn / i ζπζ / β / υ COMPONENTS OF THE INTERNAL PHASE Ingredient % by weight active % by weight in the final concentrated composition % active by weight in the final concentrated composition Acetochlor 95.80 31.57 30.24 ISOPAR M (solvent, isoalkanes CnCie) 100 1.63 1.63 DESMODUR N 3215 (aliphatic isocyanate based on hexamethylene diisocyanate) 100 2.3 2.3 To prepare the internal phase of the acetochlor microcapsules, acetochlor was charged to a mixing vessel. The solvent ISOPAR M was then charged to the mixing vessel, followed by DESMODUR N 3215 polyisocyanate. The solution was stirred to obtain a clear, homogeneous solution. The solution could be sealed within the mixing vessel and stored until needed. Before use, the mixture was heated to 50°C in an oven. The external aqueous phase was prepared containing the components and quantities shown in Table 1-2: TABLE 1-2 COMPONENTS OF THE EXTERNAL PHASE Ingredient % by weight active % by weight in the final concentrated composition % active by weight in the final concentrated composition Glycerin 100 2.42 2.42 SOKALAN CP9 (olefin and maleic acid copolymer) 25 3.11 0.78 Ammonium caseinate 100 0.08 0.08 Citric acid 50 0.22 0.11 Water 100 34.65 34.65 triethylenetetramine (TETA) 98 0.6 0.58 To prepare the external phase, a mixing vessel was filled with water and the remaining external phase component other than TETA. The solution was stirred to obtain a clear, homogeneous solution. The solution could be sealed within the mixing vessel and stored until needed. Before use, the mixture was heated to 502°C in an oven. The interfacial polymerization medium was prepared by first charging the external phase (without TETA) into a Waring mixer vessel preheated to 50°C. The Waring commercial mixer (Waring Products Division, Dynamics Corporation of America, New Hartford, Conn., Blender 700) was supplied by a variable autotransformer from 0 to 120 volts. The mixing speed of the mixer was varied by controlling the mixer feed. The internal phase was added to the external phase over a 16-second interval, and mixing was continued to obtain an emulsion. To initiate polymerization and encapsulation of the internal phase, TETA was added to the emulsion over a period of approximately 5 seconds. The mixer speed was reduced to a vortex speed for approximately five to fifteen minutes. The emulsion was transferred to a hot plate and stirred. The reaction vessel was capped and maintained at approximately 50°C for approximately two hours, which has been found to be sufficient time for the isocyanate to react essentially completely. The capsule suspension was allowed to cool to near room temperature. The components shown in Table 1-3, except for the buffer, were premixed using a high-speed mixer (Waring mixer or Cowles dissolver). The resulting stabilizing premix was added to the capsule suspension to stabilize the dispersion of the microcapsules. Finally, the buffer was added, and the mixture was stirred for at least 15 minutes until visually homogeneous. TABLE 1-3 Stabilizing components zcconn / i ζηζ / Β / γ Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Glycerin 100 4.04 4.04 KELZAN CC (Xanthan gum) 100 0.096 0.096 Urea 50 4.5 2.25 INVALON DAM (Naphthalene sulfonate condensate) 40 7.22 2.89 AGNIQUE DFM-111S (silicone-based antifoam) 100 0.001 0.001 PROXEL GXL (1,2-benzisothiazolin-3-one solution) 100 0.06 0.06 Caustic 20 0.02 0.004 Disodium phosphate 100 0.60 0.60 This acetochlor microcapsule dispersion was prepared to have an excess molar equivalent ratio of amine molar equivalents to isocyanate molar equivalents and proportions of herbicide to shell wall components. TETA has an approximate equivalent weight of 36.6 g / mol. DESMODUR N 3215 has an approximate equivalent weight of 181 g / mol. The average particle size of the acetochlor microcapsules was approximately 10 microns. The acetochlor microcapsule dispersion was mixed with a fomesafen sodium solution. A stable concentrate was formed without phase separation. The complete aqueous concentrate composition is given below. TABLE 1-4 zccann / i ζηζ / Β / γ Composition of final aqueous herbicidal concentrate 1 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.80 31.57 30.24 Fomesafen sodium 97.70 6.88 6.72 ISOPAR M (solvent, Cu-Cie isoalkanes) 100 1.63 1.63 DESMODUR N 3215 (aliphatic isocyanate based on hexamethylene diisocyanate) 100 2.3 2.3 Glycerin 100 6.46 6.46 SOKALAN CP9 25 3.11 0.78 Ammonium caseinate 100 0.08 0.08 Citric acid 50 0.22 0.11 Water 100 34.65 34.65 triethylenetetramine (TETA) 98 0.6 0.58 KELZAN CC (xanthan gum) 100 0.096 0.096 Urea 50 4.5 2.25 INVALON DAM (naphthalene sulfonate condensate) 40 7.22 2.89 AGNIQUE DFM-111S (silicone-based antifoam) 100 0.001 0.001 PROXEL GXL (1,2-benzisothiazolin-3-one solution) 100 0.06 0.06 EXAMPLE 2 Aqueous herbicidal concentrate compositions were prepared according to the protocol described in this Example 1. The composition of each aqueous concentrate is provided in the tables below. TABLE 2-1 Composition of final aqueous herbicidal concentrate 2 Concentrate Ns 2 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98 6.86 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 0.60 0.58 Glycerin 100 6.63 6.63 Sokalan CP9 (25%) 25 3.11 0.78 Ammonium caseinate 100 0.06 0.06 Citric acid (50%) 50 0.22 0.11 Concentrate No. 2 Ingredient % by Weight Active % by Weight in Concentrate Composition % by Weight Active in Concentrate Composition Kelzan CC 100 0.096 0.096 Urea 50 4.50 2.25 Invalon DAM 40 7.22 2.89 Agnique DFM-111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium Phosphate 100 0.60 0.60 Water 100 34.51 Total 100 zcconn / i znz / B / v TABLE 2-2 Composition of final aqueous herbicide concentrate 3 Concentrated Ne 3 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98 6.86 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 1.17 0.58 Glycerin 100 6.46 6.46 Sokalan CP9 (25%) 25 3.11 0.78 Ammonium Caseinate 100 0.06 0.06 Citric Acid (50%) 50 0.22 0.11 Kelzan CC 100 0.096 0.096 Urea 50 4.50 2.25 Invalon DAM 40 7.22 2.89 Agnique DFM-111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium Phosphate 100 0.60 0.60 Water 100 34.11 Total 100.00 zcconn / i ζηζ / Β / γ TABLE 2-3 Composition of final aqueous herbicide concentrate 4 Concentrate N.9 4 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98 6.86 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 1.17 0.58 Glycerin 100 6.30 6.30 Sokalan CP9 (25%) 25 3.11 0.78 Ammonium caseinate 100 0.06 0.06 Citric acid (50%) 50 0.22 0.11 Kelzan CC 100 0.096 0.096 Urea 50 4.50 2.25 Invalon DAM 40 7.22 2.89 Agnique DFM-111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium Phosphate 100 0.60 0.60 Water 100 34.27 Total 100 TABLE 2-4 Composition of final aqueous herbicide concentrate 5 Concentrate N.9 5 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98 6.86 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 0.60 0.58 Glycerin 100 6.46 6.46 Sokalan CP9 (25%) 25 3.11 0.78 Ammonium caseinate 100 0.06 0.06 Citric acid (50%) 50 0.22 0.11 Kelzan CC 100 0.119 0.119 Urea 50 4.50 2.25 Concentrate No. 9 5 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Invalon DAM 40 7.22 2.89 Agnique DFM-111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium phosphate 100 0.60 0.60 Water 100 34.66 Total 100 zcconn / ι znz / B / v TABLE 2-5 Composition of final aqueous herbicide concentrate 6 Concentrate N.9 6 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98 6.86 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 0.60 0.58 Glycerin 100 2.38 2.38 Sokalan CP9 (25%) 25 3.11 0.78 Ammonium caseinate 100 0.06 0.06 Citric acid (50%) 50 0.22 0.11 Kelzan CC 100 0.096 0.096 Urea 50 8.58 4.29 Invalon DAM 40 7.22 2.89 Agnique DFM-111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium phosphate 100 0.60 0.60 Water 100 34.68 Total 100 zccann / ι znz / B / v TABLE 2-6 Composition of final aqueous herbicide concentrate 7 Concentrate N.9 7 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98.5 6.82 6.72 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.3 TETA 98 1.17 1.15 Glycerin 100 6.46 6.46 Sokalan CP9 25 3.11 0.78 Ammonium caseinate 100 0.08 0.08 Citric acid 50 0.22 0.11 Kelzan CC 100 0.10 0.10 Urea 50 4.50 2.25 Invalon DAM 40 7.22 2.89 Agnique DFM- 111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 3.06 0.61 Disodium phosphate 100 0.60 0.60 Water 100 31.09 Total 100 TABLE 2-7 Composition of final aqueous herbicide concentrate 8 Concentrate N.9 8 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.8 31.57 30.24 Fomesafen 98.5 5.46 5.38 Isopar M 100 1.63 1.63 Desmodur N 3215 100 2.30 2.30 TETA 98 1.17 1.15 Glycerin 100 6.46 6.46 Sokalan CP9 (25%) 25 3.11 0.78 Concentrate No. 9 8 Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Ammonium Caseinate 100 0.08 0.08 Citric Acid (50%) 50 0.22 0.11 Kelzan CC 100 0.10 0.10 Urea 50 4.50 2.25 Invalon DAM 40 7.22 2.89 Agnique DFM- 111S 100 0.001 0.001 Proxel GXL 100 0.06 0.06 Caustic (20%) 20 0.02 0.004 Disodium Phosphate 100 2.45 0.49 Water 100 35.49 Total 100 zcconn / i znz / B / v EXAMPLE 3 Various properties of the aqueous herbicidal concentrate composition prepared in Examples 1 and 2 were measured. The results of these measurements are provided in the following table. The readily extractable acetochlor is determined by extracting the concentrated composition with a weak solvent such as an aliphatic hydrocarbon solvent and analyzing the extract. Particle size was measured using a Coulter LS particle size analyzer. Viscosity was measured using a Haake Rotovisco viscometer at approximately 10 SC with a spindle rotating at approximately 45 rpm. TABLE 3-1 Properties of herbicidal concentrate compositions Concentrate No. 9 Readily Extractable Acetochlor (wt. % Total Acetochlor) Particle Size (microns) pH (neat) Specific Gravity (at 20 9C) HAAKE Viscosity (cP) 1 0.512 9.3 / 9.3 9.1 1.1241 250 2 0.749 9.7 / 9.8 8.74 1.1228 250 3 0.644 10.1 / 10.1 8.93 1.1222 251 4 0.476 9.6 / 9.7 8.96 1.1217 233 5 0.462 9.9 / 9.9 9.1 1.123 268 6 0.385 9.3 / 9.2 9.1 1.1184 167 7 Not measured ~10 7.5 1.121 225 8 Not measured ~10 7.5 1.115 250 EXAMPLE 4 The aqueous herbicidal concentrate compositions prepared in Examples 1 and 2 were subjected to a heat aging test to investigate the effects of prolonged storage on the viscosity of the compositions. A sample of each herbicidal concentrate composition was stored at 40°C for a period of 8 weeks. No gelation was observed in any of the concentrate compositions. EXAMPLES WARRANT, a commercially available concentrate composition of microencapsulated acetochlor marketed by Monsanto Co., St. Louis, Missouri, was mixed with a commercial concentrate composition of fomesafen sodium. The following table provides the composition of the mixture. The combination of these two concentrate compositions produced an unstable mixture with phase separation. zccann / i znz / B / v TABLE 5-1 Mixture of fomesafen and Warrant concentrates Ingredient % by weight active % by weight in the concentrated composition % active by weight in the concentrated composition Acetochlor 95.80 31.57 30.24 Fomesafen sodium 97.70 6.88 6.78 ISOPAR M (solvent, isoalkanes Ci 1 -Cte) 100 1.63 1.63 DESMODUR N 3215 (Aliphatic isocyanate based on hexamethylene diisocyanate) 100 2.3 2.3 Glycerin 100 7.19 7.19 SOKALAN CP9 25 2.16 0.54 Ammonium caseinate 100 0.04 0.04 Citric acid 50 0.16 0.08 Water 100 33.30 33.30 triethylenetetramine (TETA) 98 0.6 0.58 KELZAN CC (xanthan gum) 100 0.05 0.05 Urea 50 8.28 4.14 INVALON DAM (naphthalene sulfonate condensate) 40 5.60 2.24 AGNIQUE DFM-111S (silicone-based antifoam) 100 0.001 0.001 PROXEL GXL (1,2-benzisothiazolin-3-one solution) 100 0.05 0.05 Caustic 20 0.02 0.004 Disodium phosphate 100 0.17 0.17 EXAMPLES A series of field trials were conducted at various locations. Soil texture at these sites ranged from silt loam, clayey silt loam, and sandy loam. The objective of the experiment was to evaluate the weed efficacy and duration of residual efficacy of each individual herbicide compared to herbicide combinations. Experiments were conducted in a randomized complete block design. Four replications were conducted per treatment. Application to weeds was pre-emergence, and treatments were applied using an overhead or backpack sprayer. Application mixtures prepared from concentrate composition 7 described in Example 2 were applied under field conditions at an application rate of 1,363 lb of active ingredient (ai) per acre. For comparison, field trials were also conducted with application mixtures of fomesafen and WARRANT.Percent weed control by weed species was observed four weeks after treatment (WAT). Weed control was determined as a percentage compared to untreated plants following a conventional procedure where a specially trained person made a visual assessment of plant mortality and growth reduction. Between field trials, results were recorded for 16 broadleaf and 7 narrowleaf weed species. These included ABUTH (mallow) in 9 trials; AMATA / AMAPA (palmer amaranth / water hemp), glyphosate-resistant AMAPA / AMATA (GR), IPOSS (morning glory sps.), and ECHCG (Echinochola sps.) in 5 trials; DIGSS (Digitaria sps.) in 4 trials; CASOB (skunkweed), CHEAL (common ragweed), and AMBEL (common ragweed) in 3 trials; POROL (purslane), MOLVE (carpetweed), SETFA (giant foxtail), and SORHA (Aleppo sorghum) in 2 trials; ACCOS (copperleaf hophornbeam), EPHSS (Euphorbia sps.), HIBTR (Venetian mallow), SIDSP (prickly sid), BRASS (wiregrass sps.), SORSS (sorghum sps.), and PESGL (pearl millet) in 1 trial. The results of the field trials are presented in Tables 6-1 and 6-2. The average percent control and standard error were estimated using the least squares method. A summary of results for a second field trial with similar weed species four weeks after treatment is presented in Table 6-3. zcconn / i znz / B / v TABLE 6-1 Weed species control for acetochlor, fomesafen and N.g7 concentrate in field trial 1 Weed Type Weed Species WARRANT (acetochlor) 1.125 lb / acre Fomesafen 0.25 lb / acre Concentrate Ns 7 1.363 lb / acre % Control (Average) Standard Error r % Control (Average) Standard Error r % Control (Average) Standard Error Broadleaf ABUTH 55.6 5.8 63.7 5.8 75.5 5.8 ACCOS 80.0 1.0 93.8 1.0 92.5 1.0 AMAPA 71.9 4.8 92.5 4.8 100.0 4.8 AMAP G 80.5 7.8 87.8 7.8 96.6 7.8 AMATA 78.3 8.2 85.8 8.2 91.7 8.2 AMATG 47.5 7.1 57.5 7.1 68.8 7.1 AMBEL 67.5 11.6 75.8 11.6 79.2 11.6 CASOB 44.2 15.3 46.2 15.3 49.3 15.3 CHEAL 54.6 11.8 78.3 11.8 70.8 11.8 EPHSS 85.0 1.6 100.0 1.6 100.0 1.6 HIBTR 70.0 5.0 75.0 5.0 85.0 5.0 IPOHE 52.5 10.8 52.5 10.8 72.5 10.8 IPOLA 35.0 4.0 27.5 4.0 35.0 4.0 IPOSS 46.9 19.0 63.1 19.0 76.8 19.0 MOLVE 87.1 4.1 90.6 4.1 96.5 4.1 POROL 66.3 11.6 66.3 11.6 62.5 11.6 SEBEX 27.5 8.3 33.8 8.3 55.0 8.3 SIDSP 93.8 2.6 98.3 2.6 100.0 2.6 BRASS 97.5 3.1 99.5 3.1 96.0 3.1 DIGSA 90.8 9.5 65.3 9.5 97.4 9.5 DIGSS 96.3 2.8 99.0 2.8 100.0 2.8 ECHCF 98.1 7.0 71.9 7.0 99.9 7.0 ECHC G 89.5 12.0 66.8 12.0 96.0 12.0 PESGL 52.5 2.2 100.0 2.2 100.0 2.2 SETFA 72.5 15.6 58.8 15.6 72.5 15.6 SORHA 65.5 10.6 86.8 10.7 90.6 10.6 SORSS 90.0 2.2 99.8 2.2 100.0 2.2. TABLE 6-2 zcconn / i znz / B / v Compendium of field trial results 1 Field Trial 1 Active Ingredient Application Rate (Ib ai / acre) Broadleaf Control Narrowleaf Control Fomesafen 0.25 (0.28 kq / hectare) 70 79 WARRANT 1.125 (1.26 kq / hectare) 61 85 Concentrate Ns 7 1.363 (1.53 kq / hectare) 77 94 (fomesafen acetochlor) + zcconn / i znz / B / v TABLE 6-2 Compendium of field trial results 2 Field Trial 2 Active Ingredient Application Rate (Ib ai / acre) Broadleaf Control Narrowleaf Control Fomesafen 0.25 (0.28 kq / hectare) 63.6 66.3 WARRANT 1.125 (1.26 kg / hectare) 43.2 86.2 Concentrate Ns 7 (fomesafen + acetochlor) 1.363 (1.53 kg / hectare) 77 88.8 EXAMPLE 7 In this example, the effect of fomesafen on the solubility of acetochlor was measured at various fomesafen concentrations. The results are shown in Table 7-1. TABLE 7-1 Solubility of acetochlor in fomesafen solutions Fomesafen Solution Concentration (% by weight) Acetochlor Concentration in solution (% by weight) 0 0.04 10 0.45 20 1.36 30 1.91 40 1.94 When presenting elements of the present invention or preferred embodiments thereof, the articles "a," "the," and "said" are intended to refer to one or more of the elements. The terms "comprising," "including," and "featuring" are intended to be inclusive and refer to the possibility of additional elements beyond those listed. Considering the foregoing, it will be seen that the various objectives of the invention are achieved and other beneficial results are obtained. Since various changes can be made to the compositions and methods without departing from the scope of the invention, it is intended that all material contained in the foregoing description be interpreted as illustrative and not limiting. Once the invention has been described in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

Claims

1. An aqueous herbicide concentrate composition comprising: microcapsules comprising an acetanilide herbicide, wherein the concentration of the acetanilide herbicide in the composition on an active ingredient basis is at least 25% by weight; a water-soluble protoporphyrinogen oxidase inhibitor (PPO inhibitor); a structure-breaking agent in a concentration of not more than approximately 3.5% by weight; and a density-adjusting agent, wherein the total concentration of structure-breaking agent and density-adjusting agent is approximately 7% by weight to approximately 10% by weight.

2. The aqueous herbicide concentrate composition of claim 1, wherein the total concentration of structure-breaking agent and density-adjusting agent is approximately 7.5% by weight to approximately 9% by weight.

3. The aqueous herbicide concentrate composition of claim 1 or 2, wherein the structure-breaking agent comprises urea.

4. The aqueous herbicide concentrate composition of any one of claims 1 to 3, wherein the density adjusting agent comprises glycerin.

5. The aqueous herbicide concentrate composition of any one of claims 1 to 4, wherein the concentration of the structure-breaking agent is at least approximately 1% by weight.

6. The aqueous herbicide concentrate composition of any one of claims 1 to 5, further comprising a pseudoplastic thickener.

7. The aqueous herbicide concentrate composition of claim 6, wherein the concentration of the pseudoplastic thickener is at least approximately 750 ppm.

8. The aqueous herbicide concentrate composition of claim 6 or 7, wherein the concentration of the pseudoplastic thickener is less than approximately 2000 ppm.

9. The aqueous herbicide concentrate composition of claim 8, wherein the concentration of the pseudoplastic thickener is from approximately 900 ppm to approximately 2000 ppm. zcconn / i ζπζ / β / υ 10. The aqueous herbicide concentrate composition of any one of claims 6 to 9, wherein the pseudoplastic thickener comprises a water-soluble gum selected from the group consisting of guar gum, xanthan gum and a combination thereof.

11. The aqueous herbicide concentrate composition of any one of claims 1 to 10, wherein the weight ratio of the total acetanilide herbicide to the PPO inhibitor is approximately 1:10 to 10:

1.

12. The aqueous herbicide concentrate composition of any one of claims 1 to 11, wherein the concentration of the acetanilide herbicide in the aqueous phase is from approximately 0.5% to approximately 10% of the total weight of the acetanilide herbicide.

13. The aqueous herbicide concentrate composition of any one of claims 1 to 12, wherein the concentration of acetanilide herbicide in the composition on an active ingredient basis is at least approximately 30% by weight.

14. The aqueous herbicide concentrate composition of any one of claims 1 to 12, wherein the concentration of acetanilide herbicide in the composition on an active ingredient basis is approximately 25% by weight to approximately 40% by weight.

15. The aqueous herbicide concentrate composition of any one of claims 1 to 14, wherein the weight ratio of total acetanilide herbicide to PPO inhibitor on an acid equivalence (ae) basis is approximately 1:10 to 10:

1.

16. The aqueous herbicide concentrate composition of any one of claims 1 to 15, wherein the weight of the herbicide acetanilide is greater than the weight of the PPO inhibitor on an acid equivalence basis.

17. The aqueous herbicide concentrate composition of claim 16, wherein the weight ratio of the total acetanilide herbicide to the PPO inhibitor on an acid equivalence basis is from approximately 2:1 to approximately 10:

1.

18. The aqueous herbicide concentrate composition of any one of claims 1 to 17, wherein the acetanilide is selected from the group consisting of acetochlor, alachlor, butachlor, butenachlor, delachlor, diethyl, dimetachlor, mefenacet, metazochlor, metolachlor, S-metolachlor, pretylachlor, propachlor, propisochlor, prinachlor, terbuchlor, tenylchlor and xylachlor, mixtures thereof and stereoisomers thereof.

19. The aqueous herbicide concentrate composition of any one of claims 1 to 18, wherein the acetanilide is selected from the group consisting of acetochlor, alachlor, butachlor, metolachlor, and S-metolachlor. zcconn / i znz / B / v 20. The aqueous herbicide concentrate composition of any one of claims 1 to 19, wherein the acetanilide is selected from the group consisting of acetochlor, metolachlor and S-metolachlor.

21. The aqueous herbicide concentrate composition of any one of claims 1 to 20, wherein the acetanilide comprises acetochlor.

22. The aqueous herbicide concentrate composition of any one of claims 1 to 21, wherein the concentration of the PPO inhibitor on an active ingredient basis is at least approximately 2% by weight.

23. The aqueous herbicide concentrate composition of any one of claims 1 to 21, wherein the concentration of the PPO inhibitor on an active ingredient basis is from approximately 2% by weight to approximately 20% by weight.

24. The aqueous herbicide concentrate composition of any one of claims 1 to 23, wherein the PPO inhibitor is selected from the group consisting of acifluorfen, azaphenidine, bifenox, butaphenacil, carfentrazone-ethyl, flufenpyr-ethyl, flumiclorac, flumiclorac-pentyl, flumioxazine, fluoroglycophene, flutiacet-methyl, fomesafene, lactophene, oxadiargil, oxadiazone, oxyfluorfen, pyrafluphen-ethyl, saflufenacyl, and sulfentrazone, salts and esters thereof, and mixtures thereof.

25. The aqueous herbicide concentrate composition of any one of claims 1 to 24, wherein the water-soluble PPO inhibitor is selected from the group consisting of water-soluble salts of fomesafene and acifluorfen.

26. The aqueous herbicide concentrate composition of any one of claims 1 to 25, wherein the water-soluble PPO inhibitor comprises sodium fomesafene.

27. The aqueous herbicide concentrate composition of any one of claims 1 to 26, wherein the microcapsules comprising the herbicide acetanilide comprise a polyurea cover wall.

28. The aqueous herbicide concentrate composition of claim 27, wherein the polyurea shell wall is formed in a polymerization medium by a polymerization reaction between a polyisocyanate component comprising a polyisocyanate or mixture of polyisocyanates and a polyamine component comprising a polyamine or mixture of polyamines to form the polyurea.

29. The aqueous herbicide concentrate composition of claim 28, wherein the polyisocyanate component comprises an aliphatic polyisocyanate.

30. The aqueous herbicide concentrate composition of claim 28 or 29, wherein the ratio of amine molar equivalents contained in the polyamine component to isocyanate molar equivalents contained in the polyisocyanate component zcconn / i znz / B / v is at least approximately 1.1:

1.

31. The aqueous herbicide concentrate composition of claim 28 or 29, wherein the ratio of amine molar equivalents contained in the polyamine component to isocyanate molar equivalents contained in the polyisocyanate component is from 1.1:1 to approximately 1.7:

1.

32. The aqueous herbicide concentrate composition of claim 28 to 31, wherein the weight ratio of the herbicide acetanilide to the hull wall is approximately 13:1 to approximately 6:

1.

33. The aqueous herbicide concentrate composition of any one of claims 1 to 32, wherein the microcapsules have an average particle size of at least approximately 2 pm.

34. The aqueous herbicide concentrate composition of any one of claims 1 to 33, wherein the microcapsules have a mean particle size range of approximately 2 pm to approximately 15 pm.

35. The aqueous herbicide concentrate composition of any one of claims 1 to 34, wherein the concentration of the herbicide acetanilide in the aqueous phase is from approximately 0.5% to approximately 5% by weight of the total herbicide acetanilide.