IL32256A - Compositions containing a beta-di-lower alkylamino lower alkylene thioether or a salt thereof,and their use as herbicides - Google Patents

Description

( 103 >*?^Κ)-*Ί-Κ03 Jmaill Q^DBH o'-psan *» oi D ona vizpvni ,nVe n1?© ικ mm*n *p»3 i *f^ COMPOSITIONS CONTAINING A β-DI-LOWER AXKYLAMINO LOWER AIEILSIE ΤΗΣΟΒΤΗΕΠ OR A 3AXT THEREOF, AND THEIR ITSB SOM CORPORATION DOCKET 1-1288 The present invention relates to a novel class of selective herbicidal compositions. The present invention further relates to processes for selectively controlling the growth of certain pest weeds without substantially adversely affecting the growth of valuable crop plants.

The invention is advantageous in that it makes possible the growth of corn, oats, soybeans, wheat, and the like in fields which are made free or substantially free of common pest weeds.

The term "herbicidal compositions" as used herein is intended to compositions mean and to refer to a novel class of oompounde which have specific herbicidal activity against certain hereinafter defined pest weeds without substantially affecting the growth of valuable crops.

The terms "pre-emergent herbicide" or "pre-emergent herbicidal composition" as used herein are intended to mean and to refer to -eeiopaaRds-«ar compositions which when applied to or incorporated in soils containing pest weeds seeds and in which valuable crop seeds have been planted but have not emerged will selectively prevent, impair, or inhibit the germination and/or growth of a wide variety of undesirable pest weeds without substantially adversely affecting the growth of the crop plants.

The terms "post-^emergent herbicide" or "post-emergent herbicidal composition" as used herein are intended to mean and to refer to compositions which when applied to fields, containing growing crops and pest weeds will selectively kill or substantially damage a wide variety of undesirable pest weeds without substantially adversely affecting the growth of crop plants.

The invention provides a herbicidal composition comprising a compound selected from the group consisting of: (a) a /.-di-lower alkylamino lower alkylene thioether of the formul s where Alk is a straight or branched alkyl group containing from U-16 carbon atoms, R is lower alkylene, and RV and R" are like or dissimilar lower alkyl, and (b) stable salts thereof.

Compositions falling within the scope above described can have selective pre-emergent and/or post-emergent herbicidal activity, that is, certain of the compounds are selective pre-emergent herbicides while others are selective post-emergent herbicides.

The herbicidal activity of compounds falling within the scope of this invention is unexpected since similar compounds have strong general, rather than selective, post-emergent phytotoxic properties and other similar compounds have no herbicidal activity. Certain compounds falling within the scope above described are selective pre-emergent herbicides and certain other compounds of the invention are selective post-emergent herbicides.

In compounds represented by the above formula, Alk is a straight or branched alkyl group containing from li-l6 carbon atoms. If this alkyl group contains less than h or more than l6 carbon atoms, the compounds sometimes lose their herbicidal effectiveness or the herbicidal selectivity against weeds.

Examples of Alk include n-butyl, tert-butyl, sec-butyl, and pentyl, hexyl, and heptyl, octyl, nonyl, decyl, undecyl, and dodecyl and their branched isomers. Of these alkyl groups, compounds wherein Alk is n-octyl 3>.7-dimethyl octyl (e.g., a branched decyl) and compounds wherein Alk is b,0,8-trimethyl nonyl (e.g., a branched dodecyl isomer) have been ound to be particularly advantageous as hereinafter described.

Also in compounds represented by the above formula, R is lower alkylene and is preferably ethylene, propylene, or butylene for economic reasons. R' and R" are like or dissimilar lower alkyl and are preferably like lower alkyl because of the difficulty in preparing compounds in which R* and R" are unlike. Re and R" are preferably like lower alkyl and are more preferably methyl, ethyl, propyl or butyl because of the ready availability of these alkyl substituents.

Compounds falling within the scope of the above-described formula have limited water solubility but are soluble in conventional solvents commonly used in the agricultural pesticide art. However, the above compounds can be made water soluble without substantially altering their herbicidal activity by converting them into stable salts by treatment with an appropriate acid such as, for example, hydrochloric, hydrobromic, sulfuric, and phosphoric acids to form the corresponding hydrochloride, hydrobromide, acid sulfate, or acid phosphate salts. Such stable salts are effectively soluble in water. The compounds as well as their salts can be applied to soils and/or plants in the form of aqueous solutions either alone or in conjunction with a carrier, such as those hereinafter defined, or with a water soluble fertilizer.

Preferred salts are hydrohalide salts such as, for example, the hydrochloride or hydrobromide since these have been found to be particularly effective against common pest weeds. Examples of specific compounds falling within the scope of the selective herbicides of this invention are : 8-dimethylaminoethyl n-octyl thioether, #-diethylaminoethyl n-octyl thioether, £-diethylaminoethyl 3>7-dimethyl octyl thioether, ^S-dipropylaminoethyl n-octyl thioether, /S-dipropylaminoethyl 3>7-dimethyl octyl thioether, β-dipropylaminoethyl l*,6,8-trimethyl nonyl thioether, 6-dibutylaminoethyl n-octyl thioether, β-dibutylaminoethyl 3>7-dimethyl octyl thioether, ,^-dibutylaminoethyl -j,6,6 trimethyl nonyl thioether, /3-diethylaminopropyl n-octyl thioether, 8 -diethylaminopropyl 3>7-dimethyl octyl thioether, β -diethylaminopropyl -,6,8«trimethyl nonyl thioether, β -diethylaminobutyl n-octyl thioether, β -diethylaminobutyl 3>7-dimethyl octyl thioether, β -diethylaminobutyl U,6,8-trimethyl nonyl thioether, ^-dipropylaminopropyl n-octyl thioether, -dipropylaminopropyl 3,7-dioctyl thioether, In addition to the above, other advantageous specific compounds include the corresponding hydrohalide, hydrogen sulfate, and hydrogen phosphate salts of each of the foregoing compounds.

The foregoing compounds include -dialkylaminoalkyl octyl thioethers, /&-dialkylaminoalkyl decyl thioethers, and /0-dialkylaminoalkyl dodecyl thioethers wherein the more advantageous of the octyl group of the thioethers are unbranched straight chain groups or radicals; the more advantageous decyl thioethers are branched decyl groups or radicals (e.g., the 3*7-dimethyl octyl thioethers); and the more advantageous dodecyl thioethers contain branched dodecyl groups or radicals.

As will be evident from the specific examples, the octyl and decyl thioethers are selective pre-emergent and post-emergent herbicides and when used pre-emergently, will permit the substantially uninhibited growth of cotton, corn, soybeans, and wheat while killing or severely damaging crabgrass, rye grass, barngrass, pigweed, and buckwheat when applied to soils at a level of between about 8 and about 10 lbs. of thioether per acre of soil. When used post-emergently, that is, to fields in which valuable crops such as corn, oats, soybeans, cotton, and buckwheat are growing, the herbicides will kill or damage mustard, yellow foxtail, barngrass, crab-grass, and morning glory without substantial damage or inhibition of the growth of the aforementioned crop plants.

On the other hand, although dodecyl thioethers exhibit limited pre-emergent herbicidal activity, they kill or substantially injure pest weeds such as mustard, yellow foxtail, barngrass, crabgrass , and morning glory when post-emergently applied to crop fields in which these weeds are growing without substantially affecting the growth of corn, oats , soybeans, or cotton.

The compounds of this invention can be used along or can be incorporated in and used in conjunction with a carrier. Such a carrier can be an inert carrier or diluent or a different type of soil treating agent such as, for example, a commercial fertilizer.

The inert diluents or carriers include a wide variety of organic and inorganic liquid, solid, or semi-solid carrier or carrier formulations conventionally used in herbicidal formulations . Examples of liquid organic carriers include liquid aliphatic hydrocarbons , such as pentane, hexane, heptane, nonane, decane , and their analogs as well as liquid aromatic hydrocarbons such as , for example, xylenes . Other liquid hydrocarbons include oils produced by the distillation of coal and/or the distillation of various types and grades of petroleum stocks.

Petroleum oils are especially desirable and include kerosene oils, that is, oils composed of hydrocarbon mixtures of low molecular weight (e . g. , 10-16 carbon atoms ) which are obtained by fractional distillation between" 360 °F. and 510 °F. and which usually have a fraction point between 15*0° F. and 185 °F. Other petroleum oils include those generally referred to in the art as agricultural spray oils and are light and medium oils which consist of the middle fractions of the distillation of petroleum and usually have a viscosity in the range of from h0-8$ sec , Saybolt at 100 °F. , and are only slightly volatile. These oils are usually refined and contain only minute amounts of unsaturated compounds as measured by standard sulfonation tests. The customary sulfonation range of such oils is between 90% and 9h% unsulfonatable residue. Such oils, often referred to as paraffin- type oils , are advantageous in that they can be emulsified with water and used in controlled concentrations in sprays . Tall oils obtained from the sulfate digestion of wood pulp may also be employed.

In addition to the above-mentioned liquid hydrocarbons and usually used in conjunction therewith, the carrier can contain a conventional emulsifying agent, such as, for example, an ethylene oxide condensate of an alkyl phenol or anionic surfactant such as an alkali metal salt of an alkyl-benzene sulfonic acid. Such emulsifiers are added and used to enable the compositions to be diluted with water for end use applications.

Usually when paraffin oils are employed, an emulsifier is included in the mixture (e.g., ether, paraffin oil, and emulsifier) and is diluted with water just prior to end use application, fbr example, when certain hereinafter water insoluble compounds falling within the scope of this invention are dissolved in a paraffin oil containing an emulsifier and such compositions are diluted with water to form an oil-in-water emulsion, the resulting emulsion when atomized and sprayed on soils containing planted crop seeds and undesirable volunteer weed seeds prior to the emergence of the seeds will prevent the normal emergence of the undesirable volunteer weeds without damage or injury or prevention of the normal emergence of crop seeds from the soil after germination. On the other hand, certain other hereinafter defined water insoluble compounds falling within the scope of this invention are similarly dissolved, emulsified and sprayed on fields containing growing crops and weeds. The weeds will be killed or damaged to the exclusion of substantial adverse effects upon the growing crop plants.

Other advantageous organic carriers include liquid terpene hydrocarbons and alcohols such as -φ-pinene, dipentene, terpineol, and the like. Still other liquid carriers include organic solvents such as aliphatic and aromatic alcohols, aldehydes and ketones. Suitable aliphatic monohydroxy alcohols include glycols such as ethylene and propylene glycol and the pinacols, for example, the alcohols having the formula ^Η-^,ίΟΗ^· Suitable polyhydroxy alcohols include glycerol, sorbitol, erythritol, * arabitol and the like. Suitable cyclic alcohols include, for example, cyclopentanyl and cyclohexyl alcohols „ Aromatic and aliphatic esters, aldehydes and ketones are often used in combination with the above-mentioned alcohols. Still other liquid $ carriers include higher boiling petroleum products such as mineral oil and higher molecular weight alcohols such as cetyl alcohol (sometimes referred to as "liquid waxes") may also be employed.

Solid carriers which may be employed in the compositions of this invention include finely divided organic and inorganic solid materials.

Examples of finely divided solid inorganic carriers include siliceous materials such as clays, for example, Bentonite, Attapulgite, Fullers earth, diatomaceous earth, kaolin, mica, talc and finely divided quartz as well as synthetically prepared siliceous materials such as precipitated and fume silicas and silica aromated gels. 1$ Other examples of finely divided solid inorganic carriers include commercial fertilizers, for example, inert fertilizers containing potassium phosphorous and nitrogen which are both water soluble and water insoluble, suitable examples of which are described in "Encyclopedia of Chemical Technology" by Kirk-Othmer, Volume 9> pages 25-17, published by Inter- 20 science Publishers of New York, Inc., January 1966.

Examples of finely divided solid organic materials include starch, flour, sugar, powdered sawdust, casein, gelatin and the like. Examples of semi-solid organic carriers include petroleum jelly, lanolin and the like and mixtures of these with any of the above-defined solid and liquid carriers 2$ and emulsifiers when desired.

Compositions containing in combination the compounds of this invention and the above-described diluents can be employed per se, or can be diluted with suitable liquids or can be applied to the soil in liquid or dust form and mixed with the soil by conventional agricultural cultivation techniques.

The present invention also provides a method of selectively controlling undesirable plant growth which comprises applying to an environment to which a crop has been planted an amount of a compound falling within the scope of the hereinbefore described formula, effective for substantially inhibiting the growth of pest weeds without substantially inhibiting the growth of seed crops, said amount not being substantially in excess of 10 lbs. per acre.

The amount of herbicidal compound of this invention which may be applied to an environment, preferably a soil environment (although sand may sometimes constitute the environment), will vary considerably depending upon the particular crop planted, the kind of pest weeds indigenous to the particular environment and whether the material is to be used pre -emergen tly or poet-emergently.

Generally, the amount will not be substantially in excess of lbs. of herbicidal compound per acre of soil. If more than 10 lbs. of herbicidal compound per acre are applied per acre of soil, certain crops may be damaged . If less than about 2.5 lbs . of herbicidal compound are applied per acre of soil, certain weeds may not be killed or sufficiently damaged, thus lessening the effectiveness of the treatment.

Where the compounds are used pre-emergently, from about 8 to about 10 lbs. of compound per acre of soil are desirably employed. On the other hand, where the compounds are employed post-emergently, from about 2-1/2 to about 5 lbs. of compound per acre of soil are usually effective in killing or inhibiting the growth of common pest weeds without damage to crop plants. Although in the case of certain plants such as corn, up to and more than 10 lbs. per acre of the compounds of this invention can be applied without adversely affecting the plants, other plants such as soybeans and cotton, although not killed, may exhibit some stunted or inhibited growth.

The following specific examples are intended to illustrate the invention but not to limit the scope thereof, parts and percentages being by weight unless otherwise specified.

EXAMPLE 1 /e-diethylaminoethyl n-octyl thioether and its hydrochloride salt were tested for selective pre-emergent herbicidal activity using the following standard agricultural screening procedure for pre-emergent herbicides.

Five sets of seven separate individual 3" square plastic containers filled with standard compost soil having a pH of 6.3 to 6.5, having an organic matter content of h- 2% and containing, respectively, newly planted seeds of cotton, corn, soybeans, wheat, crabgrass, rye grass, and pigweed were watered and held for 2h hours. Thereafter, an acetone solution containing 0»$% by weight of ^-diethylaminoethyl n-octyl thioether was prepared. Also prepared was a 0.5$ aqueous solution of /&-diethylaminoethyl n-octyl thioether hydrochloride« The soil of the first group of seven containers was sprayed with 0.5 ml. of the acetone thioether solution to provide an amount of thioether equivalent to an application of U lbs. of thioether per acre of soil.

The soil of each of the second group of seven containers was sprayed with 1.0 ml. of the ?-diethylaminoethyl n-octyl thioether acetone solution to provide an amount of ether equivalent to an application of 8 lbs. of thioether per acre of soil.

The soil of each container of the third group of seven containers was sprayed with 0.5 ml. of the aqueous solution of £-diethylaminoethyl n-octyl thioether hydrochloride to provide an amount of thioether hydrochloride equivalent to an application of I lbs. per acre of soil.

The soil of each of the fourth group of seven containers was sprayed with 1.0 ml. of the aqueous solution of ^-diethylaminoethyl n-octyl thioether hydrochloride to provide a thioether hydrochloride equivalent to an application of 8 lbs. per acre of soil.

The fifth group of containers served as controls, were watered and received no treatment.

All of the groups of containers were then placed in a greenhouse, observed daily for 28 days after the pre-emergent treatment. In the first and second groups of containers (e.g., those containers receiving an equivalent of k and 8 lbs. of thioether per acre), the crabgrass, rye grass, and pigweed were significantly injured and a majority of the plants died, the remainder growing to less than one-third of their normal size. The growth of cotton, corn, soybean, and wheat plants was substantially unaffected. When compared with corresponding plants in the containers of the fifth or untreated control group, no difference was observable between the plants.

In the third and fourth groups of containers (e.g., those receiving treatment equivalent to h and 8 lbs. per acre of the aqueous solution of thioether hydrochloride), the pest weed plants (e.g., crabgrass, rye grass, and pigweed) were killed or damaged to substantially the same extent as those in the first and second groups whereas the cotton, corn, soybean, and wheat plants were substantially unaffected. The untreated controls (e.g., containers containing cotton, corn, soybean, and wheat plants) were the same as those plants in the first four groups. The untreated control pest weed containers (e.g., those containing crabgrass, rye grass, and pigweed) were normal and had grown to three times the height of the surviving pest weed plants at the end of the experiment.

EXAMPLE 2 The procedure of Example 1 was repeated except that ^-diethyl- aminoethyl 3»7-dimethyloctyl thioether and the corresponding hydrochloride salt were employed in place of the n-octyl thioether and hydrochloride employed in Example 1. The results obtained were substantially identical with those of Example 1.

It is evident that while compounds of this invention selectively kill certain plants such as crabgrass and rye grass, they do not affect wheat plants which are also classified among the grass plants.

EXAMPLE 3 f?-diethylaminoethyl n-octyl thioether and i s hydrochloride salt were tested for selective post-emergent herbicidal activity using the following standard agricultural screening procedure for post-emergent herbicides.

Pour groups of nine separate individual disposable " square containers were filled with standard soil and the containers of each group seeded according to growth requirement schedules containing, respectively, newly planted corn, oats, soybeans, cotton, buckwheat, mustard, crabgrass, and morning glory. When the crop plants (e.g., corn, oats, clover, soybean, cotton, and buckwheat) and weed plants (e.g., mustard, yellow foxtail, barngrass, crabgrass, and morning glory) had reached a growth development characterized by the first true leaf stage, they were placed in carrying trays and treated. An acetone solution containing 0.6$ by weight of 8-ethylaminoethyl n-octyl thioether and an aqueous solution containing ,6% by weight of the corresponding ether hydrochloride was prepared.

Each of the first group of nine containers was sprayed with 2.0 ml. of acetone solution to provide an amount of thioether application equivalent to 10 lbs. per acre of soil.

Each of the second group of nine containers was sprayed over the surface of the soil with 1.0 ml. of acetone solution to provide an amount of thioether application equivalent to $ lbs. of thioether per acre of soil.

Each of the third group of nine containers was sprayed with 0.5 ml. of acetone solution to provide an amount of thioether application equivalent to 2.5 lbs. of thioether per acre of soil.

The fourth group served as a control and received no treatment.

After treatment, the plants were observed daily, final observation being made lh days after treatment. Such observations included all abnormal physiological responses such as stem bending, petiol curvature, epinasty, hyponasty, retardation, stimulation, root development, necrosis, and related growing regulant characteristics.

In the group of containers which received y#-diethylaminoethyl 1-octyl thioether in an amount equivalent to 10 lbs. per acre, all pest weeds (e.g., mustard, yellow foxtail, barngrass, crabgrass, and morning glory) were either killed or severely damaged. On the other hand, corn was unaffected and grew identically to that of the fourth group of controls. Oats, soybeans, and cotton showed a slight growth retardation but were otherwise not adversely affected.

In the group of containers to which the ether was applied to the plants in amounts equivalent to 5> lbs. and 2.5 lbs. per acre, mustard, morning glory, and crabgrass were killed, whereas yellow foxtail and barn-grass were significantly damaged. Corn and oat plants were unaffected.

The soybean plants and cotton exhibited a slight growth retardation when compared with the group of the fourth controls. The results of this experiment were unexpected in that morning glory was killed by the 5 and 2.5 lbs. per acre applicationj cotton and clover were not lithically affected .

EXAMPLE h The procedure of Example 3 was repeated except that the /8-diethylaminoethyl n-octyl thioether hydrochloride was employed in aqueous solution in place of the 0-diethylaminoethyl n-octyl thioether in an acetone solution as employed in Example 3. The results were substantially identical to those obtained in Example 3.

In following the foregoing Examples 1-h, when the ^-dimethyl or S-dipropylaminoethyl n-octyl thioethers or their corresponding acid phosphate or acid sulfate salts were used in place of the corresponding respective herbicides employed in those examples, substantially the same results were obtained. When the corresponding ^-diethylaminopropyl or aminobutyl compounds are employed, substantially the same herbicidal results are obtained.

EXAMPLE $ β -dimethylaminoethyl li,6,8-trimethyl nonyl thioether and its hydrochloride salt were tested for pre-emergent herbicidal activity using the procedure described in Example 1. The results showed that both crop plants and weed plants which had been treated with an equivalent of h lbs. of herbicide per acre grew normally. However, those crop plants (e.g., cotton, corn, soybeans, and wheat) which had been treated with an equivalent of 8 lbs. of herbicide per acre grew normally, but crabgrass, rye grass, and buckwheat plants, although not killed, showed growth inhibition of about one-half that of the untreated control weed plants. The results of this experiment indicated that ^-dimethylaminoethyl h,6,8-trimethyl nonyl thioether and its hydrohalide salt are partially effective as pre-emergent herbicides in amounts of 8 lbs. of herbicide per acre.

EXAMPLE 6 -diethylaminoethyl 1,6,8-trimethyl nonyl thioether and its hydrochloride salt were tested for selective post-emergent herbicidal activity using the procedure of Example 3. The results of this test showed that corn and oats which had been treated with the herbicide in an amount equivalent to 2, 5 and 10 lbs. per acre grew normally. Soybean plants, cotton, clover, and buckwheat which had been treated with a material in an amount equivalent to $ and 10 lbs. per acre showed some slight inhibition of growth, but those plants which had been treated with the herbicide in an amount equivalent to 2.5 lbs. per acre exhibited substantially normal growth. Of the pest weeds treated with the herbicide, mustard, crabgrass, and morning glory plants were all killed by the herbicide at all levels. Barngrass plants which had been treated with an equivalent of 10 lbs. per acre were killed, and barngrass plants which had been treated with 2-1/2 and 5 lbs. per acre grew only to about one-half the size of the normal untreated control barngrass plants. Yellow foxtail plants, while not killed at any of the treatment levels, grew to about one-third of the size of the untreated control yellow foxtail plants when treated at a rate of 10 lbs. per acre of herbicide, and those plants which had been treated with 2.5 and lbs. per acre grew to about one-half the size of the untreated controls .

When the corresponding hydrobromide salts were employed in place of the hydrochloride salts following the procedure of Example 5, substantially the same results were obtained.

The results of Examples 5 and 6 demonstrate that 0-diethyl-aminoethyl ,o,8-trimethyl nonyl thioether, which is actually a branched dodecyl thioether, has limited pre-emergent herbicidal activity at the levels employed but is an effective post-emergent herbicidal compound when employed at between about 2 and about J? lbs. of herbicide per acre of soil in which crops are to be grown or are growing.

EXAMPLE 7 The procedure of Example 1 was repeated exept that prior to the planting of the seeds, there was sprayed on the soil the same amounts of the 8-dLethylaminoethyl n-octyl thioether and the soil was cultivated to mix the herbicide therein. The results of this experiment showed that crop plants grew normally in soils which had been treated with an equivalent of h lbs. of herbicide per acre of soil. None of the pest weeds were killed but growth was discernibly inhibited in all instances. In soils which had been so treated with an equivalent of 8 lbs. per acre, cotton, soybeans, and wheat grew normally. Crabgrass and buckwheat plants were not killed at this level but grew to about one-fourth of their normal size. ¾re grass plants grew to about one-half to two-thirds of their normal size (e.g., the size of the untreated controls).

Claims (1)

1. DKT. 1-1288 1, A herbicidal composition comprising a compound selected from the group consisting of s (a) a β -di -lower alkylamino lower alkylene thioether of the formula : Alk - S - R - N XR» where Alk is a saturated alkyl group containing from I4. to 16 carbon atoms, R is lower alkylene, and RJ and R" are like or dissimilar lower alkyly and (b) stable salts thereof 0 2c, A composition of the formula of claim 1, wherein Alk is octyl, decyl, branched decyl, dodecylr or branched dodecyl. 3» A composition of the formula of claim 1, where R is ethylene and R' and R" are like lower alkyl 0 .4., The composition of claim 3, where, in said formula.- R' and R" are ethyl. 5o The composition of claim 1, where said compound is β -diethylaminoethyl n-octyl thioethere 6„ The composition of claim 2, where said compound is β -diethylaminoethyl 3^7-dimethyloctyl thioether. 7¾ The composition of claim 6, where said compound is β -diethylaminoethyl ij.,6, 8-trimethylnonyl thioether, 8. The composition of claim 1? where the salt of said compound is the hydrohalide , 9« The composition according to any one of the pre-ceding claims, consisting essentially of a herbicidally effective amount of said compound and a carrier therefor. lOe The composition according to any one of the preceding claims, wherein said carrier is essentially inert, lie The composition of any of the preceding claims 1 to 9? wherein said carrier comprises a fertilizer. 12. The method of selectively controlling undesirable plant growth, which, comprises applying to an environment in which a crop has been planted an amount of the composition according to any of the preceding claims effective for substantially inhibiting the growth of pest weeds without substantially inhibiting the growth, of said crop5 said amount not being substantially in excess of 10 lbs. per acre, 13. The method of claim 12, wherein said composition comprises a compound selected from the group consisting of s (a) ^-diethylaminoe h l n-octyl thioether, (b) ^f-diethylaminoethyl i}.,6, 8-trimethyl nonyl tbio ether, and (c) stable salts thereof. 1Ιμ9 The method of selectively controlling undesirable AS claimed in claim 12 plant growth/substantially as described,