GB2193634A - Herbicidal compositions containing a tetrazole compound and methods of combating plant growth - Google Patents

Abstract

A herbicidal composition comprises a tetrazole compound of the general formula I:- <IMAGE> where R<1> represents a phenyl group which is unsubstituted or substituted by a halogen atom, or by a amino group, or by an alkyl, alkoxy or haloalky group having up to 4 carbon atoms, or R<2> represents a phenyl group optionally substituted by a halogen atom, or by a nitro group, or by an alkyl or haloalkyl group having up to 4 carbon atoms, (hereinafter referred to as compound A), together with at least one compound selected from (i) 2-chloro-4-(1-cyano-1-methylethylamino-)-6-ethylamino 1,3,5-triazine. (ii) 1-(benzothiazol-2-yl)-1,3-dimethyl urea (iii) a compound which has the general formula II <IMAGE> wherein R3 represents a chlorine atom or a methyl, isopropyl or methoxy group, R4 represents a hydrogen or chlorine atom and R5 represents a methyl or methoxy group (iv) 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine (v) methyl- or isopropyl-N-benzoyl-N-(3-chloro-4-fluorophenyl)-alaninate. (vi) Compound of the general formula I:- <IMAGE> where R6 represents a chlorine atom or a methoxycarbonyl group.

Description

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

1-Aryl-5-aryloxy-1H-tetrazole compounds are disclosed for weed control in European Patent Application No. 149269 A. It has been found that the herbicidal activity of such compounds can be enhanced by admixture with certain other types of herbicidal compounds, the mixtures exhibiting unexpected properties.

The invention provides a herbicidal composition which comprises a tetrazole compound of the general formula I:

where R' represents a phenyl group which is unsubstituted or substituted by a halogen atom, or by a amino group, or by an alkyl, alkoxy or haloalkyl group having up to 4 carbon atoms, or R2 represents a phenyl group optionally substituted by a halogen atom, or by a nitro group, or by an alkyl or haloalkyl group having up to 4 carbon atoms, (hereinafter referred to as compound (A), together with at least one compound selected from (i) 2-chloro-4-(1-cyano-1-methylethylamino-)-6-ethylamino 1,3,5-triazine (commonly known as cyanazine); (ii) l-(benzothiazol-2-yl)-1 ,3-dimethyl urea (commonly known as methabenzthiazuron);; (iii) a compound which has the general formula II

wherein R3 represents a chlorine atom or a methyl, isopropyl or methoxy group, R4 represents a hydrogen or chlorine atom and R5 represents a methyl or methoxy group (for example, including compounds commonly known as linuron, isoproturon, chlortoluron and metoxuron); (iv) 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzeneamine (commonly known as trifluralin); (v) methyl- or isopropyl-N-benzoyl-N-(3-chloro-4-fluorophenyl)alaninate (commonly known as flamprop-methyl and flamprop-isopropyl); (vi) a compound which has the general formula Ill

wherein R6 represents a chlorine atom or a methoxycarbonyl group (commonly known as chlorsulphuron and metsulphuron methyl).

Compounds of sections (i) to (vi) above are hereinafter referred to as compounds B.

The compositions according to the invention may contain two or more compounds A and two or more compounds B. Preferably, however, the compositions contain a single compound A together with at least one, and preferably only one, compound B.

The invention further provides a method of combating undesired plant growth at a locus, which comprises applying to the locus a compound of formula I (Compound A) and at least one compound selected from groups (i) to (vi) (Compound B) defined above.

The preferred component of formula I (Compound A) is that wherein R1 is phenyl and R2 is 3trifluoromethylphenyl; viz 1 -(3'-trifluoromethylphenyl)-5-phenoxy- 1 H-tetrazole.

The compound of group (iii) is preferably one wherein, in formula II, R3 and R4 are both chlorine atoms and R5 is a methoxy group; or R3 and R5 are both methyl groups and R4 is a chlorine atom; or R3 is a methoxy group, R4 is a chlorine atom and R5 is a methyl group; or R3 is an isopropyl group, R4 is a hydrogen atom and R5 is a methyl group.

The compound of group (v) is preferably the (R)-(-)-enantiomorph i.e. the L-alaninate, and preferably the isopropyl compound.

The weight ratio of compound A to the compound B selected from (i) to (vi) may vary widely depending on the intended application. Preferably the ratio is in the range of from 1:500 to 500:1, preferably 1:100 to 100:1 and suitably 10:1 to 1:75. Suitably the dosage of compound A applied is in the range of from 0.0001 to 2.0 kg/ha.

The composition and method of the invention may be used for the control of weeds in a wide variety of crops, depending of course on the nature of the compound B. Typical crops include, 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-emergence. For certain applications, especially when resistant weeds are present, it may be desirable also to apply a further herbicide.

The composition of this invention will normally comprise a carrier in addition to the above defined active ingredients. A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, which may for example be a plant, seed or soil, 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. Preferably compositions according to the invention contain 0.5 to 95% by weight of active ingredient.

Suitable solid carriers include 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, montomorillonites and micas; calcium carbonate; calcium sulphate; ammonium 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; and solid fertilisers, for example superphosphates.

Suitable liquid carriers includes water; alcohols, for example isopropanol and glycols; ketones, 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 application. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surface-active agent. For example the composition may contain at least two carriers, at least one of which is a surface-active agent.

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 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 example p-octylphenol or p-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 in the molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as 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 or 75% w of active ingredient and usually contain in addition to solid inert carrier, 3-10% 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 composition to that of a wettable powder but without a dispersant, and are di[uted in the field with further solid carrier to give a composition usually containing 2-10% 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 l-75% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 1-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, nonsedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-15% w of dispersing agents, 0.1-10% 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 organic liquid in which the active ingredient is substantially insoluble; certain organic soiids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or an 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 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 composition of the invention may also contain other ingredients, for example other cmpounds possessing herbicidal, insecticidal or fungicidal properties.

The following Examples illustrate the invention.

General Procedure The tests conducted were either foliar (post-emergence) spray tests, in which seedling plants were sprayed with a formulation containing the test compound, or pre-emergence tests in which soil sown with seeds of the test species is sprayed with the test formulation. Various test plant species were used, including wheat, rye grass, speedwell, chicory and corn marigoid.

The soil used in the tests was a prepared horticultural loam, irrigated throughout the test period via capillary matting.

The formulations used in the tests were prepared from solutions of the test compound or mixture in acetone containing 0.2% by weight of an alkylphenol/ethylene oxide condensate available under the trade name TRITON X-155. The acetone solutions were diluted with an equal volume of water and the resulting formulations sprayed at an application volume of 600 1/ha at 4 different dosage levels designed to produce a range of responses. Three replicate pots were used for each treatment. Untreated seedling plants were used as controls for post emergence tests, and untreated, seeded soil as controls for pre-emergence tests.

At the specified number of 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 GIRD,, dosage. If a mixture of herbicides A and B act together in an additive way, one would expect the GIRD50 values and A and B in the mixture to be given by the equations (i) and (ii) below: a GIRD,, of B in mixture (i) a Z+ b GIRD,, of A in mixture=(GIDsO of B in mixture) x Z (ii) where a=GIDsO of A used alone b=GIDso of B used alone Z=weight ratio of compound A to compound B in mixture.

By GIRD,, of A (or B) in the mixture is meant the dosage of A (or B) which is applied, in kg/ha, when a mixture which kills 50% of the test species is employed.

If only 1 component of a mixture is active against the test species at the dose rates used in the test then one would expect the GID50 values for that compound to be the same in all mixtures i.e. the other component should make no contribution to the activity (see Example 6, mixture on ryegrass).

Ifthe measured GID50 values are in fact less than the calculated values, the mixture is synergistic.

In all of the mixtures evaluated compound A was 1-(3'-trifluoromethylphenyl)-5-phenoxy-1Htetrazole. The results of the tests with different compounds as compound B are given in the following Tables, which give the GID50 values (in kg/ha) observed, and in parantheses after these observed values the values calculated according to the above equations.

The results quoted below were all subjected to analysis to assess their statistical significance and each table denotes synergism at a statistically significant level.

Example 1 This Example was a pre-emergence evaluation carried out using as Compound B the following compound: 2-chloro-4-( 1 -cyano- 1 -methylethylamino)-6-ethylamino- 1 ,3,5-triazine(cyanazine) .

The results are set out in Table 1 below.

TABLE 1

BLACKGRASS (Assessment after 10 days) Mixture Ratio A:B A B 1:0 1.47 (1.47) 0 (0) 4:1 1.10 (1.47) 0.28 (0.37) 2:1 1.22 (1.47) 0.61 (0.74) 1:1 1.09 (1.47) 1.09 (1.47) 1:2 0.97 (1.47) 1.94 (2.94) 0:1 - Example 2 This Example was a post-emergence evaluation carried out using as Compound B the following Compound: 2-chloro-4-( 1 -cyano- I-methylethylamino)-6-ethylamino- 1 ,3,5-triazine-(cyanazine). The results are set out in Table 2 below.

TABLE 2

BLACKGRASS SPEEDWELL 13 days after treatment 13 days after treatment Mixture Mixture Ratio Ratio A:B A B A:B A B 1:0 0.049 (0.049) 0 (0) 1:0 0.016 (0.016) 0 (0) 1:4 0.011 (0.023) 0.045 (0.094) 1:8 0.004 (0.009) 0.028 (0.075) 1:8 0.007 (0.015) 0.055 (0.120) 1:16 0.003 (0.007) 0.050 (0.110) 1:16 0.005 (0.009) 0.074 (0.150) 1:32 0.002 (0.004) 0.068 (0.130) 1:32 0.004 (0.005) 0.120 (0.160) 1:64 0.001 (0.002) 0.089 (0.150) 0: :1 0 (0) 0.180 (0.180) 0:1 0 (0) 0.180 (0.180) TABLE 2 continued...

CLEAVERS (Kg/ha) WHEAT (Kg?ha) 13 days after treatment 13 days after treatment Mixture Mixture Ratio Ratio A:B A B A:B A B 1:0 0.032 (0.032) 0 (0) 1:0 1.100 (1.100) 0 (0) 1:1 0.010 (0.017) 0.010 (0.017) 1:8 0.110 (0.470) 0.90 (3.75) 1:2 0.007 (0.012) 0.014 (0.023) 1:16 0.059 (0.300) 0.94 (4.76) 1:4 0.004 (0.007) 0.016 (0.028) 1:32 0.043 (0.170) 1.37 (5.51) 1:8 0.004 (0.004) 0.032 (0.032) 1:64 0.039 (0.093) 2.49 (5.98) 0:1 0 (0) 0.036 (0.036) 0::1 0 (0) 6.53 (6.53) Example 3 The Example was a pre-emergence evaluation carried out using as Compound B the following compound: 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine (trifluralin). The results are set out in Table 3 below.

TALE 3

WHEAT 15 days after treatment Mixture Ratio A:B A B 1:0 51.38 (51.38) 0 (0) 8:1 7.66 (9.46) 0.96 (1.18) 4:1 3.95 (5.21) 0.99 (1.30) 2:1 2.43 (2.75) 1.21 (1.37) 1:1 1.17 (1.41) 1.17 (1.41) 0:1 o (o) 1.45 (1.45) Example 4 This Example was a pre-emergence evaluation carried out using as Compound B the following compound: 3-(4-isopropylphenyl)-1,1-dimethylurea (isoproturon). The results are set out in Table 4 below.

TABLE 4

ANNUAL MEADOW GRASSES 19 days after treatment Mixture Ratio A A B 1:0 0.041 (0.041) 0 (0) 4:1 0.016 (0.021) 0.004 (0.005) 2:1 0.010 (0.014) 0.005 (0.007) 1:1 0.007 (0.009) 0.007 (0.009) 1:2 0.003 (0.005) 0.006 (0.010) 0:1 0 (O) 0.011 (0.011) Example 5 This example was a post-emergence evaluation carried out using as Compound B the following compound:- 3-(4-isopropylphenyl)-1,1,-dimethylurea (isoproturon). The results are set out in Table 5 below.

TABLE 5

BLACKGRASS ANNUAL MEADOW GRASS 7 days after treatment 7 days after treatment Mixture Mixture Ratio Ratio A:B A B A:B A B 1:0 0.10 (0.10) 0 (0) 1:0 0.28 (0.28) 0 (0) 1:2 0.046 (0.066) 0.092 (0.13) 2:1 0.077 (0.25) 0.039 (0.12) 1:4 0.017 (0.049) 0.067 (0.20) 1:1 0.075 (0.22) 0.075 (0.22) 1:8 0.011 (0.032) 0.086 (0.26) 1:2 0.054 (0.18) 0.11 (0.36) 1:16 0.006 (0.019) 0.093 (0.31) 1:4 0.043 (0.13) 0.17 (0.52) 0::1 0 (0) 0.38 (0.38) 0:1 0 (0) 0.97 (0.97) Example 6 This example was a pre-emergence evaluation carried out using a Compound B the following compound:- 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (linuron). The results are set out in Table 6 below: TABLE 6

BLACKGRASS SPEEDWELL 20 days after treatment 20 days after treatment Mixture Mixture Ratio Ratio A:B A B A:B A B 1:0 0.51 (0.51) 0 (0) 1:0 0.24 (0.24) 0 (0) 4:1 0.71 (0.51) 0.18 (0.13) 1:1 0.15 (0.17) 0.15 (0.17) 2:1 0.37 (0.51) 0.19 (0.26) 1: :2 0.11 (0.13) 0.23 (0.27) 1:1 0.44 (0.51) 0.44 (0.51) 1:4 0.08 (0.09) 0.30 (0.37) 1:2 0.15 (0.51) 0.30 (1.02) 1:8 0.04 (0.06) 0.33 (0.46) 0:1 - - 0:1 0 (0) 0.60 (0.60)

Claims (9)

1. A herbicidal composition comprises a tetrazole compound of the general formula I:

where R' represents a phenyl group which is unsubstituted or substituted by a halogen atom, or by a amino group, or by an alkyl, alkoxy or haloalkyl group having up to 4 carbon atoms, or R2 represents a phenyl group optionally substituted by a halogen atom, or by a nitro group, or by an alkyl or haloalkyl group having up to 4 carbon atoms, (hereinafter referred to as compound A), together with at least one compound selected from (i) 2-chloro-4-(1-cyano-1-methylethylamino-)-6-ethylamino 1 ,3,5-triazine.

(ii) 1-(benzothiazol-2-yl)-1,3-dimethyl urea (iii) a compound which has the general formula II

wherein R3 represents a chlorine atom or a methyl, isopropyl or methoxy group, R4 represents a hydrogen or chlorine atom and R5 represents a methyl or methoxy group (iv) 2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine (v) methyl- or isopropyl-N-benzoyl-N-(3-chloro-4-fluorophenyl)-alaninate.

(vi) a compound which has the formula

wherin R6 represents a chlorine atom or a methoxycarbonyl group.

2. A composition according to claim 1 wherein the compound of formula 1 is 1-(3'-trifluoromethylphenyl)-5-phenoxy-1 H-tetrazole.

3. A composition according to claim 1 or 2 wherein, in the compound of formula II, R3 and R4 are both chlorine atoms and R5 is a methoxy group; or R3 and R5 are both methyl groups and R4 is a chlorine atom; or R3 is a methoxy group, R4 is a chlorine atom and R5 is a methyl group; or R3 is an isopropyl group, R4 is a hydrogen atom and H5 is a methyl group.

4. A composition as claimed in any one of claim 1 to 3 wherein the weight ratio of compound A to the compound(s) selected from groups (i) to (vi) is within the range of from 1:500 to 500:1.

5. A method of combating undesired plant growth at a locus, which comprises applying to the locus a compound of formula I as defined in claim 1 or 2 and at least one compound selected from groups (i) to (vi) as defined in claims 1 or 3.

6. A method as claimed in claim 5, in which the compounds are applied in the form of a composition as claimed in any one of claims 1 to 4.

7. A method as claimed in claim 5 or 6 wherein the locus treated is a crop area bearing plants or seeds of cereals.

8. A herbicidal composition substantially as hereinbefore described with reference to the foregoing description.

9. A method of combating undesired plant growth, substantially as hereinbefore described.