SYNERGISTIC HERBICIDAL COMPOSITIONS AND METHODS OF USE.

Abstract: A synergistic herbicidal composition comprising a mixture of an herbicidally effective amount of a thiolcarbamate as defined herein, an herbicidally effective amount of a benzamide as defined herein, and the agriculturally acceptable salts thereof, all admixed with an agricultural­ ly acceptable carrier, diluent, or adjuvant therefor.

Description: Background of the Invention The protection of crops from weeds and other vegetation which inhibit crop growth is a constantly recurring problem in agriculture. To help combat this problem researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use. In some cases, active herbicides have been shown to be more effective in combination than when applied individually. The result is often termed "synergism", since the combination demonstrates a potency or activity level exceeding that which it would be expected to have, based on a knowledge of the individual potencies of the components. The present invention resides in the discovery that certain thiolcarbamates and cer­ tain substituted benzamide compounds, already known individually for their herbicidal potency, display this synergism when applied in combination. Prior Art The two classes of compounds forming the compositions which are the subject of the present invention are independently known in the art for their effects on plant growth. The first of the two classes, thiolcarbamates, are disclosed as herbicides in U.S. Patent Nos. 3,185,720 (Tilles et al., May 25, 1965), 3,198,786 (Tilles et al., Aug. 3, 1965), and 2,913,327 (Tilles et al., Nov. 17, 1959). The substituted benzamide compounds forming the second class of compounds in the compositions of the present invention are presently com­ mercially available, and are described in U.S. Patent 4,416,813. Description of the Invention It has now been discovered that synergism in the control of undesirable vegetation is exhibited by compositions comprising a mixture of the following components: (a) an herbicidally effective amount of a thiolcarbamate of the formula in which X is hydrogen, chlorine or bromine; and R¹ and R² are independently selected from the group consisting of C₁-C₆ alkyl and C₅-C₇ cycloalkyl, and (b) an herbicidally effective amount of a benzamide of the formula wherein R¹ is hydrogen or C₁-C₄ alkoxy; R² is C₁-C₄ alkylthio or C₁-C₄ alkoxy; R³ is C₁-C₄ alkyl, C₁-C₄ alkylthio or C₁-C₄ alkoxy; R⁵ is wherein R⁶ is C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl, C₁-C₆ alkoxy or C₁-C₆ alkylthio; y is an integer from 0 to 5; R⁷ and R⁸ independently are C₁-C₁₃ alkyl or halo-C₁-C₁₃ alkyl; wherein R⁹ and R¹⁰ independently are hydrogen, halogen, C₁-C₄ alkyl or C₁-C₄ alkenyl; Q¹ and Q² independently are CH₂; and the agriculturally acceptable salts thereof, all admixed with an agriculturally acceptable carrier, diluent or adjuvant therefor. The term "alkyl" is used herein to denote both straight-chain and branched-chain groups. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, etc. All carbon atom ranges are inclusive of their upper and lower limits. Examples of thiolcarbamates useful in the compositions and method of the present invention are: 1. S-benzyl dipropylthiolcarbamate 2. S-benzyl ethyl, 1,2-dimethylpropylthiolcarbamate 3. S-(2-chlorobenzyl)-N,N-diethylthiolcarbamate 4. S-(4-chlorobenzyl)-N,N-diethylthiolcarbamate These and other thiolcarbamates within the scope of this inven­ tion can be prepared by the procedures described in U.S. Patent Nos. 2,913,327, 3,185,720, and 3,198,786 mentioned above, and U.S. Patents 3,144,475, 2,992,091 and 3,207,775. The preferred thiolcarbamate for use in the invention is S-benzyl dipropyl thiolcarbamate. The preferred benzamide for use in the compositions and method of the invention is n-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-di­ methylbenzamide, sold under the tradename EL-107, by the Elanco Company, USA. Other benzamide compounds, their salts and derivatives, which can also be used are those which are set forth below: N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[3-(tert-butyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1-ethyl-1-methylpropyl)-1,3,4-thiadiazol-1-yl]-2,6-dimethoxy­ benzamide; N-[5-(1,1-diethylpropyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[3-(1,1-dimethylpropyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[3-(1,1-diethylhexyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1-ethylheptyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[3-(1,1-diethylheptyl)-5-isoxazolyl]-2,6-dimethoxybenazmide; N-[3-(1-ethyl-1-methylbutyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[3-(2,2-diethylbutyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1-methylbutyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[5-(1-ethyl-1-methylhexyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[3-(1,1-dimethyltetradecyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1,2-dimethylbutyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[5-(1,2-diethylhexyl)-3-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1,1,2-trimethylbutyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[3-(1,1,2,2-tetramethylbutyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[3-(1-ethylhexyl)-5-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1-ethyl-1-methylpentyl)-3-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1,1-diethyldecyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[5-(1-isopropylcyclohexyl)-3-isoxazolyl]-2,6-dimethoxybenzamide; N-[5-(1-methylcyclopropyl)-1,3,4-thiadiazol-2-yl]-2,6-dimethoxybenzamide; N-[5-(1-ethylcycloheptyl)-1,3,4-thiadiaol-2-yl]-2,6-dimethoxybenzamide; and N-[3-(1-isopropylcyclopentyl)-5-isoxazolyl]-2,6-dimethoxybenzamide. The terms "synergism" and "synergistic" are used herein to con­ vey the result observed when a combination of herbicides demonstrates a potency in excess of that which the combination would be expected to pro­ duce on the basis of the potencies of each herbicide applied individually. In the compositions of this invention, the thiolcarbamate:benza­ mide weight ratio at which the herbicidal response is synergistic lies within the range of about 75:1 to about 20:1. The synergism is especial­ ly observed when the compositions are used against broadleaf weeds growing among barley and winter wheat. Application rates will depend upon the weeds to be controlled and the degree of control desired. In general, the compositions of this invention are most efficiently employed at a rate of 0.01 to 50 pounds per acre (0.01 to 56 kilograms per hectare) of the active ingredients, prefer­ ably 0.1 to 25 pounds per acre (0.11 to 28 kilograms per hectare). The compositions are particularly effective in pre-emergence control of Galium aparine and Matricaria . The method of this invention, therefore, comprises applying a herbicidally effective amount of the synergistic compositions of the invention to the locus where control is described. The synergistic herbicidal activity of the compositions is illustrated in Example I below. EXAMPLE I The herbicidal responses from a combined use of S-benzyl di­ propylthiolcarbamate (Compound 1) and N-[3-(1-ethyl-1-methylpropyl)-5-iso­ xazolyl]-2,6-dimethylbenzamide, EL-107 (Compound 2) were studied by means of a field test. A series of field test plots were prepared and planted with win­ ter wheat and winter barley. The test herbicidal compositions were then applied to the soil in pre-emergence of the crops and weeds at the rate indicated by diluting commercial formulations of the respective herbicides with water and applying at the predetermined rate. The following weed pest species were seeded along side the wheat and barley. Avena spp . wild oats (AVESS) Galium aparine bedstraw (GALAP) Viola arvenis field pansy (VIOAR) Alopecurus myosuroides black grass (ALOMY) Veronica hederifolia ivy leaved speedwell (VERHE) In addition to the foregoing, the following naturally occurring weed specie, which also grew up along side the wheat and barley crop plants, was treated with the herbicidal compositions of this invention. Matricaria spp. mayweed (MATSS) Water was used to dilute all the herbicide compositions. The chemical solutions were delivered to the soil by pre-emergence application with a tank sprayer. Ratings were made 106 days after treatment. At that time, the control and test plots were compared to the standards and each plot was rated visually in terms of percent control ranging from 0% to 100%, with 0% representing the same degree of growth as the same plot in the standard and 100% representing complete kill of all weeds in the plot. All types of plant injury were taken into considera­ tion. For the weed species, the results of these tests are listed in Table 1 in the columns headed by the symbol "O" (indicating the "observed" results), each figure representing the average of two replications of the same test. These results are compared with the results, shown in the columns headed by the symbol "E", derived from the control data using Limpel's formula (Limpel et al., 1962, "Weed Control by Dimethylchloro­ terephthalate Alone and in Certain Combinations," Procee. NEWCC., Vol. 16, pp. 48-53): E = X + Y - where X = observed percent injury when one of the herbi­ cides is used alone, and y = observed percent injury when the other herbicide is used alone. It is clear from the table that synergism was observed at many of the application rates tested. The compositions of the present invention show synergistic activity as herbicides in controlling the growth of undesirable vegetation when applied to such vegetation in pre-emergence application. By "pre­ emergence" is meant application to the soil surface application prior to the time of emergence of the target weed therefrom. The compositions are generally embodied in formulations which contain inert or occasionally active ingredients or diluent carriers in addition to the active com­ pounds. Examples of such ingredients or carriers are water, organic sol­ vents, surface active agents, oil, water-inoil emulsions, wetting agents, dispersing agents, and emulsifying agents. The herbicidal formulations generally take the form of wettable powders, dry flowables, solutions or emulsifiable concentrates. Wettable powders and dry flowables are finely divided composi­ tions comprising a particulate carrier impregnated with the herbicidal compound and additionally containing one or more surface active agents. The surface active agent promotes rapid dispersion of the powder in aque­ ous medium to form stable, sprayable suspensions. A wide variety of sur­ face active agents can be used, for example, long chain fatty alcohols and alkali metal salts of the sulfated fatty alcohols; salts of sulfonic acid; esters of long chain fatty acids; and polyhydric alcohols, in which the alcohol groups are free, omega-substituted polyethylene glycols of rela­ tively long chain length. The herbicidal compositions can also be applied to the soil and foliage in the form of a solution in a suitable solvent. Solvents fre­ quently used in herbicidal formulations include kerosene, fuel oil, xylene, petroleum fractions with boiling ranges above xylene, and aromatic petroleum fractions rich in methylated naphthalenes. The most preferred formulations are suspension concentrates (flowables), which consist of suspensions of solid particles in a (contin­ uous) liquid medium, which can be aqueous or non-aqueous. Typical co­ formulants will be wetting agents, dispersants, suspending agents, viscos­ ity building agents, anti-cooling agents, ant9-freezing and anti-foaming agents. The formulations described above can be applied to the locus where control is sought in any conventional manner before the vegetation has emerged from the soil. Application can be achieved by any convention­ al technique such as the use of ground spraying equipment or aircraft-­ mounted sprayers. Various other application techniques will be apparent to one skilled in the pesticide art.

Claims: 1. A synergistic herbicidal composition comprising a mixture of (a) an herbicidally effective amount of a thiolcarbamate of the formula in which X is hydrogen, chlorine or bromine; and R¹ and R² are independently selected from the group consisting of C₁-C₆ alkyl and C₅-C₇ cycloalkyl, and (b) an herbicidally effective amount of a benzamide of the formula wherein R¹ is hydrogen or C₁-C₄ alkoxy; R² is C₁-C₄ alkylthio or C₁-C₄ alkoxy; R³ is C₁-C₄ alkyl, C₁-C₄ alkylthio or C₁-C₄ alkoxy; R⁵ is wherein R⁶ is C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl, C₁-C₆ alkoxy or C₁-C₆ alkylthio; y is an integer from 0 to 5; R⁷ and R⁸ independently are C₁-C₁₃ alkyl or halo-C₁-C₁₃ alkyl; wherein R⁹ and R¹⁰ independently are hydrogen, halogen, C₁-C₄ alkyl or C₁-C₄ alkenyl; Q¹ and Q² independently are CH₂; and the agriculturally acceptable salts thereof, all admixed with an agri­ culturally acceptable carrier, diluent, or adjuvant therefor. 2. The composition of Claim 1 wherein (a) is S-benzyl dipropyl thiolcarbamate and (b) is N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-­ dimethoxybenzamide. 3. The composition of Claim 1 wherein (a) is S-benzyl ethyl, 1,2-dimethylpropyl thiolcarbamate and (b) N-[3-(1-ethyl-1-methylpropyl)-5-­ isoxazolyl]-2,6-dimethoxybenzamide. 4. The composition of Claim 1 wherein (a) is S-(2-chloro­ benzyl)-N,N-diethyl thiolcarbamate and (b) N-[3-(1-ethyl-1-methylpropyl)-­ 5-isoxazolyl]-2,6-dimethoxybenzamide. 5. A method of controlling undesirable vegetation which com­ prises the pre-emergence application to said vegetation of a herbicidal composition comprising a mixture of (a) an herbicidally effective amount of a thiolcarbamate of the formula in which X is hydrogen, chlorine or bromine; and R¹ and R² are independently selected from the group consisti­ of C₁-C₆ alkyl and C₅-C₇ cycloalkyl, and (b) an herbicidally effective amount of a benzamide of the formula wherein R¹ is hydrogen or C₁-C₄ alkoxy; R² is C₁-C₄ alkylthio or C₁-C₄ alkoxy; R³ is C₁-C₄ alkyl, C₁-C₄ alkylthio or C₁-C₄ alkoxy; R⁵ is wherein R⁶ is C₁-C₄ alkyl, C₂-C₄ alkenyl, C₂-C₄ alkynyl, C₁-C₆ alkoxy or C₁-C₆ alkylthio; y is an integer from 0 to 5; R⁷ and R⁸ independently are C₁-C₁₃ alkyl or halo-C₁-C₁₃ alkyl; wherein R⁹ and R¹⁰ independently are hydrogen, halogen, C₁-C₄ alkyl or C₁-C₄ alkenyl; Q¹ and Q² independently are CH₂; and the agriculturally acceptable salts thereof, all admixed with an agri­ culturally acceptable carrier, diluent, or adjuvant therefor. 6. The method of Claim 5 wherein (a) is S-benzyl dipropyl thiolcarbamate and (b) is N-[3-(1-ethyl-1-methylpropyl)-5-isoxazolyl]-2,6-­ dimethoxybenzamide. 7. The method of Claim 5 wherein (a) is S-benzyl ethyl, 1,2-di­ methylpropyl thiolcarbamate and (b) is N-[3-(1-ethyl-1-methylpropyl)-5-­ isoxazolyl]-2,6-dimethoxybenzamide. 8. The method of Claim 5 wherein (a) is S-(2-chlorobenzyl)-N,N-­ diethyl thiolcarbamate and (b) is N-[3-(1-ethyl-1-methylpropyl)-5-isoxa­ zolyl]-2,6-dimethoxybenzamide.

Inventors: BALLAUX, JEAN-CLAUDE, HINDERSMANN, ULLI
Applicants: STAUFFER CHEMICAL COMPANY
Application year: 1987
Main classification: A01N47
IPC codes: A01N43, A01N47