HK1065923B - Herbicidal synergistic composition and method of used control - Google Patents

Description

Herbicidal synergistic composition and weed control method

The application is a divisional application of Chinese patent application CN98106340.3 with the application date of 26.1/1998 and the invention name of 'weeding synergistic composition and weed control method'.

The present invention relates to novel herbicidal synergistic compositions comprising a combination of herbicidally active ingredients, said compositions being suitable for the selective control of weeds in crops of useful plants, such as in cereals, cotton, soya, sugar beet, sugar cane, plantation crops, grapes, maize and rice. The invention further relates to a method for controlling weeds in crops of useful plants and to the use of the novel compositions for this purpose.

The compounds of formula I have herbicidal activity.

The following compounds are also known herbicides, and some of them are also commercially available: the formula (III) compound is shown in the specification,

wherein U-V is a group of the formula: r₁C＝N，N＝CR₁，CONR₁，R₁NCO or R₁C＝CR₂Wherein R is₁is-NHC₃H₇- (iso), -NHC (CH)₃)₂CN，-NHC₄H₉- (tert) -, -NHC₂H₅，-SCH₃，

Or

W-Y is a group of the formula: CR₂＝N，CONR₂，NR₂CO，CONR₃Or CR₂＝CR₃Wherein R is₂Is methyl, -Cl, -NH₂，-NHC₃H₇- (hetero) or NHC₂H₅And R₃is-NHCH₃Or C₄H₉- (tert), and R is-Cl, -SCH₃，-C₄H₉- (tert), methoxy, hydroxy, N (CH)₃)₂，CHF₂Or hydrogen; or U-V-W-Y together form a group-C (CF)₃)＝C(R₄)-C(CH₂-C₃H₇- (iso)) ═ C (R)₅) -, wherein R₄is-COSCH₃Or

And R⁵Is COOCH₃Or COSCH₃It is known, for example, from the handbook of pesticides, 10 th edition, british crop protection committee 1994, 32, 51, 565, 840, 740, 239, 956, 699, 959, 962, 974 and 375.

Surprisingly, it has now been found that a combination of two active ingredients in different ratios, i.e. the active ingredient of formula I in combination with the active ingredient of formula III described above, has a synergistic effect which enables the control of the occurrence of most weeds, especially in useful crops, pre-and post-emergence, without significantly damaging the useful crops. According to the invention, therefore, novel synergistic compositions for selective weed control are proposed which, in addition to the conventional inert formulation adjuvants, contain as active ingredient a compound of the formula I

In admixture with a synergistically effective amount of at least one compound selected from the group of substances of the formula III and salts thereof,

wherein U-V is a group of the formula: r₁C＝N，N＝CR₁，CONR₁，R₁NCO or R₁C＝CR₂Wherein R is₁is-NHC₃H₇- (iso), -NHC (CH)₃)₂CN，-NHC₄H₉- (tert) -, -NHC₂H₅，-SCH₃，

Or

W-Y is a group of the formula: CR₂＝N，CONR₂，NR₂CO，CONR₃Or CR₂＝CR₃Wherein R is₂Is methyl, -Cl, -NH₂，-NHC₃H₇- (iso) or-NHC₂H₅And R₃is-NHCH₃Or C₄H₉- (tert), and R is-Cl, SCH₃，-C₄H₉- (tert), methoxy, hydroxy, N (CH)₃)₂，CHF₂Or hydrogen; or U-V-W-Y together form a group-C (CF)₃)＝C(R₄)-C(CH₂-C₃H₇- (iso)) ═ C (R)₅) -, wherein R₄is-COSCH₃Or

And R₅Is COOCH₃Or COSCH₃；

Formula F₁The sulfonylurea compound of (a) to (b),

the salts thereof corresponding to formulｃA I are known, for example, from EP-A-0103453. By reaction with a suitable salt-forming agent, formula F₁Can be converted into the compounds of the formula I in a conventional manner known per se. Such salt formers are in principle capable of forming at the group SO₂-all bases in NH-CO which remove acid hydrogen atoms. Sodium hydrides, hydroxides, alkoxides, bicarbonates and carbonates have been found to be particularly advantageous in this regard. To form a compound of formula I, formula F₁The reaction of the compounds of (a) with a base is carried out in a known manner, preferably in a protic or aprotic solvent, at room temperature or at elevated temperature, in which reaction crown ethers and/or phase transfer catalysts may be present, as described in j.march, advanced org.chem., John Wiley and Sons, fourth edition, 1992: phase transfer catalyst, described on page 362. For example, the compound of formula I can be prepared by stirring formula F at room temperature only₁The compound of (3) can be obtained in good yield in aqueous sodium hydroxide solution. Such a process is described, for example, in WO 97/41112.

Preferred compositions according to the invention are those comprising a compound of formula I and at least one compound selected from the group consisting of: ametryn, atrazine and hexazinone. Of particular note are those compositions comprising a compound of formula I and at least one compound selected from the compounds prometryn and pyridaben, in combination.

Compounds of formula III that are particularly suitable for use in compositions according to the invention are listed in Table 1:

table 1: preferred compounds of formula III:

the compounds of table 1 are referred to by the following names:

common name of compound number

1.01 Ametryn

1.02 Atlantazine

1.03 Cyclo-azinones

1.04 Pucaojing

1.05 Da Su Fu

1.06 Cyanine

1.07 pyridaben

1.08 Metribuzin

1.09 Terbutong

1.10 Terbutazine A

1.11 thiazopyr

1.12 dithiopyr

It is extremely surprising that the active ingredient combination of the formula I and the active ingredient of the formula III exceeds the theoretically predetermined additive effect on the grass to be controlled, thus expanding the range of action of the two active ingredients, in particular in both respects: first, the amount of each compound I and III applied was reduced while maintaining a high level of action. Secondly, even when used at low application rates, each compound is no longer useful from an agricultural application point of view, but the compositions according to the invention achieve a high degree of weed control. The result is a considerable broadening of the weed spectrum and an additional increase in the selectivity towards useful crops, which is necessary and desirable in the case of unintentional overdosing of the active ingredient. Moreover, the compositions according to the invention enable greater flexibility in the crop post-harvest while maintaining outstanding control of weeds in crops of useful plants. In addition, the onset of action of the compounds of formula I can be accelerated in the presence of the mixture of formula III.

The herbicidal mixtures according to the invention can be used against a large number of agriculturally important weeds, such as Stellaria, bentgrass, digitaria, Avena, Setaria, Sinapis, Virgum, Solanum, Echinochloa, Scirpus, Potentilla, Sagittaria, Aleuropa, Eugenia, sorghum halepense, Conyza, Cyperus, Abutilon, Sida, Xanthium, Amaranthus, Chenopodium, Ipomoea, Chrysanthemum, Galium, Viola and Veronica.

The herbicides according to the invention are suitable for all methods of application normally used in agriculture, such as pre-emergence application, post-emergence application and seed dressing.

The herbicidal mixtures according to the invention are particularly suitable for use in crops of useful plants such as cereals, grapes, sugar beets, sugar cane, cultivated plants (cotton), rice, maize and soybeans, more preferably sugar cane and cotton (especially after-treatment), and also for nonselective weed control.

The compositions of the invention are particularly useful for controlling weeds in the following sugarcane crops: horseweed, Convolvulus arvensis, jowar, Imperata cylindrical, Trigonella grass, commenlina benghalensis, Cyperus rotundus, scarlet caterpiller, Amaranthus retroflexus, Pharbitidis, Plantago asiatica, Digitaria villosa, Gryllus chinensis, Panicum paniculatum and Setaria viridis.

The compositions of the invention are particularly suitable for use as weeds in cotton crops: cyperus rotundus, sorghum bicolor, crabgrass, barnyard grass, cricket grass, sorghum bicolor, setaria viridis, plantago asiatica, piemarker, amaranthus retroflexus, cassia obtusifolia, chenopodium album, petunia, sesbania macrocarpa, xanthium canadensis. Furthermore, compositions comprising a compound of formula I and at least one dithiopyr are particularly suitable for use in grass. Crops are also understood to include those which are tolerant to herbicides or classes of herbicides as a result of conventional breeding or genetic engineering techniques, for example maize, soybean, cotton or sugarcane, to glyphosate, glufosinate, bromoxynil and ALS-inhibitors, such as sulfonylureas (chlorimuron-ethyl, thifensulfuron-methyl), imidazolinones (imazethapyr) or mixtures of these compounds.

The active ingredient compositions according to the invention contain the active ingredient of formula I and the active ingredient of formula III mixed in any desired ratio, usually with an excess of one over the other. Preferred mixing ratios between the active ingredient of the formula I and the mixture of the formula III are from 1: 1 to 1: 350, in particular from 1: 5 to 1: 70. The amount applied can vary widely and depends on the nature of the soil, the type of application (pre-emergence, post-emergence; seed dressing; application of interspecies furrows; non-farming application), the crop being cultivated, the weeds to be controlled, prevailing weather conditions and other factors depending on the type of application and the target crop. In general, the active ingredient mixtures according to the invention can be used at application rates of from 0.008 to 5kg/ha, in particular from 0.3 to 2kg/ha of active ingredient mixture. The mixtures of compounds of the formula I and of compounds of the formula III can be used in unaltered, i.e. synthetically obtained, form but are preferably formulated in customary manner with the auxiliaries, such as solvents, solid carriers or surfactants, customarily used in processing technology, such as directly sprayable or dilutable solutions, wettable powders, soluble powders, dusts, granules or microcapsules. Depending on the nature of the composition, the application method, such as spraying, atomizing, dusting, wetting, broadcasting or pouring, is chosen to be adapted to the intended target and prevailing weather. Formulations i.e. preparations, i.e. compositions, preparations or mixtures, which comprise a compound of formula I (active ingredient) and formula III, if appropriate, together with one or more solid or liquid formulation auxiliaries, are prepared in a known manner, e.g. by homogeneously mixing and/or grinding the active ingredient with the formulation auxiliaries, e.g. solvents or solid carriers. In addition, surface-active compounds (surfactants) can also be used in the preparation of the formulations.

Suitable solvents are: aromatic hydrocarbons, preferably fractions containing from 8 to 12 carbon atoms, such as xylene mixtures or substituted naphthalenes, phthalates, such as dibutyl or dioctyl phthalate, aliphatic hydrocarbons, such as cyclohexane or paraffins, alcohols and glycols and their ethers and esters, such as ethanol, ethylene glycol monomethyl or monoethyl ether, ketones, such as cyclohexanone, strongly polar solvents, such as N-methyl-2-pyrrolidone, dimethyl sulfoxide or N, N-dimethylformamide, vegetable oils or epoxidized vegetable oils, such as epoxidized coconut oil or soybean oil and water. Solid carriers for dusts and dispersible powders, for example, are usually natural mineral fillers, such as calcite, talc, kaolin, montmorillonite or attapulgite. To improve the physical properties of the formulation, highly dispersed silicic acid or highly dispersed absorbent polymers may be added. Suitable particulate absorbent carriers are porous types, such as pumice, broken brick, sepiolite or bentonite; suitable non-absorbent carriers are, for example, calcite or sandy soil.

In addition, a large number of impregnated materials of organic or inorganic nature can be used, such as especially dolomite or ground plant residues. Suitable surface-active compounds are, depending on the nature of the compounds of the formula I to be prepared, nonionic, anionic and/or cationic surfactants and surfactant mixtures having good emulsifying, dispersing and wetting properties. So-called water-soluble soaps and water-soluble synthetic surface-active compounds are suitable anionic surfactants. Suitable soaps are higher fatty acids (C)₁₀-C₂₂) Such as oleic acid or stearic acid, or an alkali metal, alkaline earth metal or unsubstituted or substituted ammonium salt, such as the sodium or potassium salt, of a mixture of natural fatty acids which can be obtained, for example, from coconut oil or tallow oil. Fatty acid methyl taurates are also possible. So-called synthetic surfactants are generally used, in particular fatty alcohol sulfonates, fatty alcohol sulfates, sulfonated benzimidazole derivatives or alkylaryl sulfonates. The fatty alcohol sulfonates or sulfates are usually in the form of alkali metal salts, alkaline earth metal salts or unsubstituted or substituted ammonium salts and contain C₈-C₂₂Alkyl groups, which also include the alkyl part of the acyl group, e.g. sodium or calcium lignosulphonate, and sodium or calcium dodecyl sulphateFatty alcohol sulfate mixtures from natural fatty acids. These compounds also include salts of sulfated and sulfonated fatty alcohol/ethylene oxide adducts. The sulphonated benzimidazole derivative preferably contains 2 sulphonic acid groups and one fatty acid group containing 8 to 22 carbon atoms. Examples of alkaryl sulfonates are the sodium, calcium or triethanolamine salts of dodecylbenzenesulfonic acid, dibutylnaphthalenesulfonic acid or of condensates of naphthalenesulfonic acid and formaldehyde. Corresponding phosphates, for example phosphate ester salts of p-nonylphenol adducts with 4 to 14mol of ethylene oxide, or phospholipids, are also suitable. The nonionic surfactants are preferably polyglycol ether derivatives of aliphatic or cycloaliphatic alcohols, saturated or unsaturated fatty acids and alkylphenols, said derivatives containing 3 to 30 glycol ether groups and 8 to 20 carbon atoms in the aliphatic hydrocarbon moiety and 6 to 18 carbon atoms in the alkyl moiety of the alkylphenols. More suitable nonionic surfactants are the water-soluble adducts of polyethylene oxide with polypropylene glycol, ethylenediamine polypropylene glycol and alkyl polypropylene glycols containing from 1 to 10 carbons in the alkyl chain, which contain from 20 to 250 ethylene glycol ether groups and from 10 to 100 propylene glycol ether groups. These compounds typically contain 1 to 5 ethylene glycol units per propylene glycol unit. Examples of nonionic surfactants are nonylphenol polyethoxyethanol, castor oil polyglycol ethers, polypropylene oxide/polyethylene oxide adducts, tributylphenoxypolyethoxyethanol, polyethylene glycol and octylphenoxypolyethoxyethanol. Polyoxyethylene sorbitol fatty acid esters such as polyoxyethylene sorbitol trioleate are also suitable. The cationic surfactant is preferably a quaternary ammonium salt containing an N-substituent, at least one C₈-C₂₂Alkyl groups, and also other substituted, unsubstituted or halogenated lower alkyl, benzyl or hydroxy-lower alkyl groups. Preferred salts are halides, methylsulfates or ethylsulfates, for example stearyltrimethylammonium chloride or benzyldi (2-chloroethyl) ethylammonium bromide. Surfactants which are also commonly used in conventional formulation techniques and which can also be used in the compositions according to the invention are described in particular in "Mc Cutcheon's Detergents and Emulsifiers Annual" MCpublishing Corp., Ridgewood New Jersey.1981, Stache, H., "Tensid-Taschenbuch", CarlHanser Verlag, Munich/Vienna, 1981 and MAsh, "Encyclopedia of Surfactants", Vol I-III, chemical publishing Co., New York, 1980-81.

Herbicidal formulations generally comprise from 0.1 to 99% by weight, preferably from 0.1 to 95% by weight, of the active ingredient mixture of formulae I and III, from 1 to 99.9% by weight of a solid or liquid adjuvant, and from 0 to 25% by weight, preferably from 0.1 to 25% by weight, of a surfactant. While commercial products are preferably formulated as concentrates, consumers typically use diluents. The compositions may also contain further components, such as stabilizers, for example vegetable or epoxidized vegetable oils (epoxidized coconut, rapeseed or soybean oil), antifoams, for example silicone oils, preservatives, viscosity regulators, binders, tackifiers, fertilizers or other active ingredients.

Preferred formulations consist in particular of the following components (all in weight percent)

Powder preparation

Active ingredient mixture: 0.1 to 10%, preferably 0.1 to 5%

Solid carrier: 99.9 to 90%, preferably 99.9 to 99%

Thick suspending agent

Active ingredient mixture: 5 to 75%, preferably 10 to 50%

94 to 24%, preferably 88 to 30% of water

Surfactant 1 to 40%, preferably 2 to 30%

Wettable powder

Active ingredient mixture: 0.5 to 90%, preferably 1 to 80%

0.5 to 20%, preferably 1 to 15% of a surfactant

Solid support 5 to 95%, preferably 15 to 90%

Granules

Active ingredient mixture: 0.1 to 30%, preferably 0.1 to 15%

Solid carriers 99.5 to 70%, preferably 97 to 85%

The following examples describe the invention in more detail but without limiting it.

Mixture formulations of formulae I and III (all in weight percent):

F1. solutions of a) b) c) d)

Compound I + Compound III according to Table 1 5% 10% 50% 90%

1-methoxy-3- (3-methoxy-propoxy) -propane-20% -

Polyethylene glycol molecular weight 40020% and 10-

N-methyl-2-pyrrolidone-30% to 10%

C₉-C₁₂Aromatic hydrocarbon mixture 75% 60-

The solution is suitable for microdroplets.

F2. Wettable powder a) b) c) d)

Compound I + Compound III according to Table 1 5% 25% 50% 80%

4% -3% of sodium lignosulphonate

Sodium lauryl sulfate 2% -4%

Sodium diisobutylnaphthalenesulfonate-6% 5% 6%

Octylphenol polyglycol ether (7-8 mol ethylene oxide) -1% and 2%

High-dispersion silicic acid 1%, 3%, 5%, 10%

88% of kaolin, 62% of kaolin and 35% of kaolin

The active ingredient is thoroughly mixed with the adjuvant and the mixture is thoroughly ground in a suitable mill to provide a wettable powder which can be diluted with water to give a suspension of any desired concentration.

F3. Coated particles a) b) c)

Compound I + Compound III according to Table 1 0.1% 5% 15%

High dispersion silicic acid 0.9%, 2%

99.0 percent of inorganic carrier, 93 percent and 83 percent

(AE 0.1-1mm)

Such as CaCO₃Or SiO₂

The active ingredient is dissolved in dichloromethane, the solution is sprayed onto the support, and the solvent is evaporated under vacuum.

F4. Coated particles a) b) c)

Compound I + Compound III according to Table 1 0.1% 5% 15%

The molecular weight of the polyethylene glycol is 2001.0 percent, 2 percent and 3 percent

High dispersion silicic acid 0.9%, 1%, 2%

98.0 percent of inorganic carrier, 92 percent of inorganic carrier and 80 percent of inorganic carrier

(AE 0.1-1mm)

For example CaCO₃Or SiO₂

The active ingredient, which is well ground in the mixer, is uniformly applied to the carrier moistened with polyethylene glycol. Non-dust coated granules are obtained in this way.

F5. Extruded particles a) b) c) d)

Compound I + Compound III according to Table 1 0.1% 3% 5% 15%

Sodium lignosulfonate 1.5%, 2%, 3% and 4%

Carboxymethyl cellulose 1.4%, 2% and 2%

Kaolin 97.0%, 93%, 90% and 79%

Mixing the active components, grinding with the aid, and wetting the mixture with water. The mixture was extruded and dried in an air stream.

F6. Powder preparation a) b) c)

Compound I + Compound III according to Table 1 0.1% 1% 5%

Talc 39.9% 49% 35%

60.0 percent of kaolin, 50 percent of kaolin and 60 percent of kaolin

Ready-to-use powders are obtained by mixing the active ingredient with the carrier and grinding the mixture in a suitable mill.

F7. Thick suspending agent a) b) c) d)

Compound I + Compound III according to Table 1 3% 10% 25% 50%

Ethylene glycol 5% 5%

Nonylphenol polyglycol ether (ethylene oxide 15mol) -1% 2-

Sodium lignosulfonate 3%, 4% and 5%

Carboxymethylcellulose 1% 1% 1%

37% aqueous formaldehyde solution 0.2%, 0.2%

0.8% of silicone oil emulsion, and 0.8% of silicone oil emulsion

Water 87% 79% 62% 38%

The well-ground active ingredient is thoroughly mixed with the adjuvant to give a concentrated suspension, thereby enabling suspensions of any desired concentration to be obtained by dilution with water.

The mixtures of formulas I and III were prepared separately and mixed in water in the desired ratio in an applicator shortly before application to form a tank mix.

Biological examples:

synergistic effects occur whenever the effect of the active ingredient compositions I and III is greater than the sum of the effects of the active ingredients applied individually. The desired herbicidal action, We, can be calculated for the combination of the two herbicides given by the following formula (see COLBY, s.r. "calculating synergistic and antagonistic responses in herbicidal compositions". weeds 15, pages 20-22; 1967):

We＝X+[Y·(100-X)/100]

wherein: when compared to untreated controls (═ 0%), the% herbicidal effect was observed at pkg application rates per hectare using the compound of formula I.

Y% herbicidal effect per hectare of qkg application rates using a compound of formula III compared to untreated control.

We equal the expected herbicidal effect of the application rates of p + qkg active ingredient per hectare using the compounds of formula I and III. (herbicidal action compared to untreated control%).

If the observed effect is greater than the expected effect We, then there is synergy. The synergistic effect of the combination of active ingredients I and III is demonstrated in the following example.

Example B1: pre-emergence weeding effect:

monocotyledonous and dicotyledonous weeds and cultivated crops are sown in standard soil in plastic pots. An aqueous suspension of the test compound (500 l water/ha) was applied immediately after sowing. The amount applied depends on the optimal concentration determined under field and greenhouse conditions. The calculation of the experiments was carried out in% action after 15 and 27 days (DAA ═ days after implementation). 100% means plant death and 0% means no phytotoxic effect. The active ingredients compositions of formula I and formula III showed a synergistic effect in this experiment. The following table gives examples of the pre-emergence synergy of the compositions according to the invention:

table B1: compositions of formula I and prometryn according to the invention are herbicidal pre-emergence at DAA15 The following steps are used:

application amount of 250g/ha of a compound of the formula I3.75 g/haI +250g/ha according to Colby

Test of plant 3.75g/ha prometryn expected value

Sesbania 35105042

Xanthium species 8509085

Table B2: the composition of formula I and prometryn according to the invention has a pre-emergence herbicidal action at DAA 27:

application amount of Compound of formula I250 g/ha pu 3.75g/haI +250 in accordance with Colby expectations

Test plant 3.75g/ha neat g/ha prometryn value

Crab 25108033

Sesbania 2503525

Brachypodium 25106033

Abutilon 5008550

Table B3: compositions of formula I and pyridaben according to the invention act as pre-emergent herbicides at DAA27 The following steps are used:

application rates of pyridaben of formula I3.75 g/haI according to 3.75g/haI according to

Test botanical composition 500g/ha 250g/ha +500g/ha Colby +250g/ha Colby

3.75g/ha expected value of Dictyotan

Cotton 1000010010

Abutilon 50606096809680

Sesbania 25301050483032

Xanthium species 96351098979896

In addition to the synergistic herbicidal action of the compositions according to the invention against weeds, surprisingly, a favourable antagonistic action on cultivated crop cotton was found, i.e. although the compound of formula I damages cotton by 10% when applied in an amount of 3.75g/ha, the compound of formula I, when added to 500 or 250g/ha of pyridaben, largely protects cotton (0% damage) while the herbicidal action against weeds is increased.

Example B2: post-emergence herbicidal action

The test crops were grown to the 2 to 3 leaf stage in plastic pots under greenhouse conditions. Standard soil was used as the cultivation substrate. During the 2 to 3 leaf stage, the herbicides are applied separately and then as a mixture to the test crop. The test compounds were applied as a 500 liter aqueous/ha suspension. The amount applied depends on the optimum concentration determined under field and greenhouse conditions. Trial evaluation was performed after 11 and 22 days (DAA ═ days after application). 100% means plant death and 0% means no phytotoxic effects. The active ingredients of the compositions of formula I and formula III in this experiment showed a synergistic effect. The following table gives examples of the post-emergence potentiation of the compositions according to the invention.

Table B4: the composition containing formula I and prometryn according to the invention is herbicidal after emergence of DAA22 Function of

Application rates/herbicidal action of the herbicide on Solanum nigrum according to Colby's expected value

7.5g/ha of the compound of formula I15-

3.75g/ha of a compound of the formula I0-

1.88g/ha of a compound of the formula I0-

1000g/ha prometryn 20-

500g/ha prometryn 0-

250g/ha prometryn 0-

7.5g/hal +1000g/ha prometryn 3532

7.5g/hal +500g/ha prometryn 2515

7.5g/hal +250g/ha prometryn 2515

3.75g/hal +1000g/ha prometryn 5020

3.75g/hal +500g/ha prometryn 450

3.75g/hal +250g/ha prometryn 100

1.88g/hal +1000g/ha prometryn 3020

1.88g/hal +500g/ha prometryn 250

1.88g/hal +250g/ha prometryn 250

Claims (6)

1. A herbicidal synergistic composition comprising, in addition to customary inert formulation adjuvants, a compound of the formula I

And a synergistically effective amount of at least one compound from the group consisting of prometryn, ametryn, atrazine and hexazinone,

wherein the compound of formula I is present in a weight ratio of 1: 1 to 1: 350 relative to the compound selected from the group consisting of prometryn, ametryn, atrazine and hexazinone.

2. The herbicidal synergistic composition according to claim 1, which comprises the compound of formula I and at least one compound selected from the group consisting of ametryn, atrazine and hexazinone.

3. The herbicidal synergistic composition according to claim 1, which comprises the compound of formula I and prometryn.

4. The herbicidal synergistic composition according to claim 1, wherein the compound of formula I is present in an amount of 1: 5 to 1: 70 by weight relative to the compound selected from the group consisting of prometryn, ametryn, atrazine and hexazinone.

5. A method for controlling undesired plant growth in crops of useful plants, which comprises treating the crops of useful plants with a composition as claimed in any of claims 1 to 4 at an application rate of the active ingredient in a total amount of from 0.008 to 5 kg/ha.

6. The method according to claim 5, wherein the crop of useful plants is cotton or sugarcane.