GB2114888A - Herbicidal compositions and methods of combating undesired plant growth - Google Patents

Abstract

A herbicidal composition which comprises 2,6-dinitro-N,N-dipropyl-4- trifluoromethylaniline (the herbicide trifluralin) together with 3-(3-methyl- 4-isopropylphenyl)-1,1-dimethylurea.

Description

SPECIFICATION Herbicidal composition and method of combating undesired plant growth This invention relates to herbicidal compositions and method of combating undesired plant growth.

2,6-Dinitro-N,N-dipropyl-4-triflouromethylaniline is useful as a herbicide, and is sold under the common name Trifluralin.

U.K. Patent Application No. 2064537 discloses that the compound 3-(3-methyl-4isopropylphenyl)-1 ,1-dimethylurea is effective in the control of weeds.

The Applicants have now found that mixtures of trifluralin with 3-(3-methyl-4-isopropylphenyl) 1,1 -dimethylurea exhibit an unexpected synergistic effect.

The invention therefore provides a herbicidal composition which comprises the compound 2,6 dinitro-N,N-dipropyl-4-trifluoromethylaniline (hereinafter referred to as compound I) together with 3-(3 methyl-4-isopropylphenyl)-1 ,1-dimethylurea (hereinafter referred to as compound II).

The invention further provides å method of combating undesired plant growth at a locus, which comprises applying to the locus compound I and compound II.

The weight ratio of compound I to compound il may vary widely depending on the intended application. Preferably said ratio is in the range of from 1:50 to 50:1, preferably 1:20 to 20:1 , especially 5:1 to 1:5. Suitably the dosage of each compound applied is in the range of from 0.05 to 5 kg/ha. For example, a dosage of 0.25 to 3 kg/ha of compound I may be applied together with 0.25 to 3 kg/ha of compound II.

The composition and method of the invention may be used for the control of weeds in a wide variety of crops, for example, cotton, soyabean, plantation crops such as sugar cane or vines, and, especially, cereals such as wheat, barley, maize and sorghum. A wide range of broad leaved and grassy weeds are controlled. Application may be pre-emergence or post-esnergence.

For certain applications, especially when resistant weeds are present, it may be desirable also to apply a third herbicide. For example, if severe infestations of wild oat are present in cereal crops, it may be advantageous to apply along with compound I and compound 11, one of the N,N-disubstituted alanine derivatives which are specialised narrow spectrum herbicides and described in U.K. Patent No.

1,164,160, for example the ethyl ester of N-benzoyl-N-(3,4-dichlorophenyl)-2-aminopropionic acid, or the racemic mixture or laevo rotatory isomer of the methyl or isopropyl ester of N-benzoyl-N-(3-chloro4-fluorophenyl)-2-aminopropionic acid or a broad-spectrum herbicide such as a triazine, for example cyanazine, atrazine or simazine. Further suitable compounds which may be present as a third component include metolachlor, chlortoluron, isoproturon, dichlofopmethyl, and methabenzthiazuron, phenoxyalkanoic acids such as dichlorprop, mecoprop, 2,4-D, 2,4-DB, MCPA and MCPB and their salts and esters, and compounds of the general formula:

or salts or esters thereof in which each of X1 and X2 independently represents an iodine, bromine or chlorine atom.Examples of the latter include bromoxynil and ioxynil and their respective octanoates.

A composition according to the invention preferably also comprises one or more carriers. A carrier is any material with which the active ingredients are formulated to facilitate application to the locus to be treated, or to facilitate storage, transport or handling. A carrier may be a solid or a liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating herbicidal compositions may be used.

Suitable solid carriers including natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and vermiculites; aluminium silicates, for example kaolinites, montmorillonites and micas; calcium carbonate; calcium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes, for example beeswax, paraffin wax, and chlorinated mineral waxes; and solid fertilisers, for example superphosphates.

Suitable liquid carriers include water; alcohols, for example isopropanol and glycols; for example acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarbons, for example carbon tetrachloride, perchloroethylene and trichloroethane. Mixtures of different liquids are often suitable.

Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before applicaticr;. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surface-active agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation products of fatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for examplep-octylphenol orp-octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates of these condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric or sulphonic acid esters containing at least 10 carbon atoms ir the molecule, for example sodium lauryl sulphate, sodium secondary alkyi sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as sodium dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols.

Wettable powders usually contain 25, 50 and 75% w of active ingredient and usually contain, in addition to solid inert carrier, 310% w of a dispersing agent and, where necessary, 0-10% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar compositions to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing -1 0% w of active ingredient. Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676-0.152 mm), and may be manufactured by agglomeration or impregnation techniques.

Generally, granules will contain -25% w active ingredient and 0--109/0 w of additives such as stabilisers, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 1050% w/v active ingredient, 220% w/v emulsifiers and 0--20C/o w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.

Suspension concentrates are usually compound so as to obtain a stable; non-sedimenting flowable product and usually contain 1 0-75% w active ingredient, 0.5-1 5% w of dispersing agents, 0.110% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an oryanic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as anti-freeze agents for water.

Aqueous dispersions and emulsions, for example compositions obtained by diluting a-wettable powder or a concentrate according to the invention with water, also lie within the scope of the present invention. The said emulsions may be of the water-in-oil or of the oil-in-water type, and may have a thick 'mayonnaise'-like consistency.

The compositions of the invention may also contain other ingredients, for example, compounds possessing insecticidal orfungicidal properties.

The following Example illustrates the invention.

EXAMPLE The tests conducted were foliar spray tests, in which seedling plants of weeds were sprayed with a formulation containing the test compound. The test plant species were wild oats, blackgrass and speedwell.

The soil used in the tests was prepared horticultural loam. The seedlings had 2 to 4 true leaves.

The formulations used in the tests were prepared by diluting with water, solutions of the test compound or mixture in acetone containing 0.4% by weight of an alkylphenol/ethylene oxide condensate available under the trade mark TRITON X-1 55. The acetone solutions were diluted with an equal volume of water and the resulting formulations applied at 4 different dosage levels designed to produce a range of responses. Three replicate pots were used for each treatment. Untreated seedlings plants were used as controls.

1 3 days after treatment, phytotoxicity compared with the untreated control, was assessed visually on a O to 9 scale, 0 indicating no effect and 9 indicating death.

The results were subjected to a standard probit analysis by computer to calculate the dosage of each compound or mixture, in Kg/ha, required to kill 50% of the test species. This dosage is referred to as the GID50 dosage. If a mixture of herbicides A and B act together in an additive way, one would expect the GlDso values for A and B in the mixture to be given by the equations (i) and (ii) below: a GID50 of B in mixture = (i) α + a b GIRD, of A in mixture = (GlDso of B in mixture) x a (ii) where a = GID50 of A used alone b = GID50 of B used alone a = weight ratio of compound A to compound B in mixture.

If the measured G1D50 values are in fact less than the calculated values, the mixture is synergistic.

The results of the tests are given in the following Table. The GID50 values are actual, measured values in kg/ha, and calculated values are given in brackets after the measured values. In the Table, the following abreviations are used: A: 3-(3-methyl-4-isopropylphenyl)-1 , 1 -dimethylurea.

B: 2,6-Dinitro-N,N-dipropyl-4-trifluoromethylaniline the commercial herbicide triflurali n.

The results show that the mixtures tested showed significant synergism.

TABLE OF RESULTS Speedwell GID50 Mixture Ratio A:B A B

1:0 0.37 (0.37) 0 (0) 8:1 0.27 (0.32) 0.033 (0.039) 4:1 0.16 (0.28) 0.039 (0.069) 2:1 0.13 (0.22) 0.066(0.11) 1:1 0.10(0.16) 0.10 (0.16) 0:1 0(0) 0.27 (0.27) Blackgrass GID50 Mixture Ratio A:B A B

1:0 0.013(0.013) 0 (0) 1:2 0.006(0.011) 0.011(0.021) 1:4 0.003 (0.009) 0.014(0.035) 1:8 0.003 (0.007) 0.023 (0.053) 1: :16 0.003 (0.004) 0.048 (0.072) 0:1 0(0) 0.11(0.11) Wild Oats GID50 Mixture Ratio A:B A B

1:0 0.96 (0.96) 0(0) 2:1 0.25 (0.56) 0.13 (0.28) 1:1 0.15 (0.39) 0.15 (0.39) 1:2 0.085 (0.25) 0.17 (0.49) 1A 0.081 (0.14) 0.32 (0.56) 0:1 0 (0) 0.66 (0.66)

Claims (6)

1. A herbicidal composition which comprises 2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline (compound I) together with 3-(3-methyl-4-isopropylphenyl)-1 ,1-dimethylurea (compound II).

2. A composition as claimed in claim 1, which also comprises one or more carriers.

3. A composition as claimed in claim 1, substantiaily as described in the Example herein.

4. A method of combating undesired plant growth at a locus, which comprises applying to the locus compound I together with compound II.

5. A method as claimed in claim 4, in which compound I and compound II are applied in the form of a composition as claimed in any one of claims 1 to 3.

6. A method as claimed in either claim 4 or claim 5, in which the locus treated is a crop area bearing plants or seeds of cereals.