GB2078519A - Weed control using 3-(4- isopropylphenyl)-1,1- dimethylurea in conjunction with S-2,3,3-trichloroallyl diisopropylthiocarbamate - Google Patents

Abstract

The invention provides a method for the control of the growth of grass weeds and broad-leafed weeds by application of the herbicides 3-(4- isopropylphenyl)-1,1-dimethylurea (i.e. isoproturon) and S-2,3,3- trichloroallyl diisopropylthiocarbamate (i.e. triallate) in association, the ratios of isoproturon to triallate being 2.5:1 to 1:2.5 by weight, at the application rates of 1.0 to 2.5 kg per hectare each of isoproturon and triallate by pre- or post-emergence application.

Description

SPECIFICATION Weed control using 3 (4-isopropylphenyl)-1 1 -dimethylurea in conjunction with S-2,3,3-trichloroallyl diisopropylthiocarbamate This invention relates to a new method for the control of weeds, i.e. undesired vegetation, and to new herbicidal formulations for use in the method and to processes for their preparation.

It is known that 3 (4-isopropylphenyl)-1,1-dimethylurea (hereinafter referred to as 'isoproturon') possesses valuable herbicidal properties and isoproturon is widely used in agriculture, particularly for the selective control of annual grasses, e.g. Alopecurus myosuroides, Apera spica-venti, Avena fatua and Poa annua, and a number of broad-leafed weeds, in particular the important species Stellaria media, Matricaria inodora and Papaverrhoeas, in crops of cereals, e.g.

wheat, barley and rye, by pre- or post-emergence application at application rates of 1.0 to 2.5 kg of isoproturon per hectare. (By the term 'preemergence application' is meant application to the soil in which the weed seeds or seedlings are present before emergence of the weeds above the surface of the soil. By the term 'post-emergence application' is meant application to the soil in which there are present aerial or exposed portions of weeds which have emerged above the surface of the soil). For use as a herbicide, isoproturon is commonly formulated as a flowable suspension of micronised particles, containing surfactants. These flowable suspension formulations are diluted with water at the time of application as a herbicide, to give spray fluids containing a suspension of micronised particles of isoproturon.When used atthe application rates indicated above, isoproturon gives good control of blackgrass (Alopecurus myosuroides) and the broad-leafed weeds mentioned above. However, for the effective control of wild oat (Avena fatua), it is necessary to obtain at least 90%, and preferably 95%, control in orderto reduce to acceptable levels the return of seeds from surviving plants to the soil and the use of isoproturon at the application rates indicated above is unreliable for controlling Avena fatua owing to the brief persistence of isoproturon in the soil and the extended germination period of the seeds of this weed. The use of higher rates of application of isoproturon improves the control of Avena fatua but often results in damage to the crop. In addition, the broad-leafed weed Veronica persica is resistant to isoproturon.

It is also known that S-2,3,3-trichloroallyl diisopropylthiocarbamate (hereinafter referred to as 'triallate') possesses valuable herbicidal properties and triallate is widely used in agriculture, particularly for the selective control ofAvena fatua in crops of cereals, e.g. wheat, barley and rye, by pre-emergence or early post-emergence application at application rates of 1.0 to 3.0 kg of triallate per hectare. Trial late is volatile under normal atmospheric conditions and, when applied in the form of an emulsion before or after sowing of the crop, the emulsion must be incorporated into the soil because of this volatility.

Triallate is also commonly formulated as granules, which are applied to the soil and which can be applied without incorporation into the soil, either by pre- or post-emergence application. It is believed that triallate is released from granular formulations predominantly or entirely in the form of a vapour.

The volatility and good soil persistence of triallate ensures good control ofAvena fatua under a wide range of climatic and edaphic conditions. Both emulsions and granular formulations of triallate can give useful control ofAlopecurus myosuroides when applied before the sowing of the crop or preemergence, but the granular formulations give unreliable control of this weed when applied postemergence. Attempts to improve the reliability and level of control of Alopecurus myosuroides achieved by the use of triallate by utilising application rates higher than those herein before indicated can result in crop damage. Triallate has no useful activity on broad-leafed weeds except Veronica persica.

There is a widely-recognised need in agriculture for a method of controlling bothAvena fatua and Alopecurus myosuroides together with a wide spectrum of broad-leafed weeds, including in particular Stellaria media, Matricaria inodora and Veronica persica, by the application of herbicides which is both reliable in respect of the level of weed control obtained and flexible in respect of the timing of the application of the herbicide(s). Three combinations of herbicides, each containing triallate and a herbicide of the phenylurea type have been proposed for this purpose.

(1) A granular formulation containing triallate [10% weight/weight (w!w)} and neburon [N-butyl-N' - (3,4 - dichlorophenyl) - N - methylurea; 17.5% w/w)] is proposed in French Patent Specification No. 2 287 173, published on 7th May, 1976 and by Madelon, J., Brunet, Y. and Vagneur, B., Compte Rendu de la 9, Conference du COLUMA (1977), pages 880-891. This granular formulation was applied pre-emergence at a rate of 20 kg per hectare, which corresponds to the full normal recommended dose rates of trial late (2.0 kg per hectare) and neburon (3.5 kg per hectare).The control of both grass weeds and broad-leafed weeds thus obtained was reasonable (Madelon etna!, ibid, page 886) but by no means complete and the authors (Madelonetal, ibid page 887) clearly con sider that there was no observable additive interaction between the two herbicides, i.e. the weed control obtained was that which might be expected to be produced by the pre-emergence application of triallate and neburon alone at these rates of application.

(2) Agranularformulation containingtriallate (10% w/w) and methabenzthiazuron [N-(benzo thiazol - 2 - yl) - N, - dimethylurea; 14% wlw)] is described by Madelonetal, ibid., and by Michel, F., Pourcharesse, P. and Madelon J., Compte Rendu de la 9, Conference du COLUMA (1977), pages 892-901.

This granular formulation was applied preemergence or early post-emergence (up to the 3-leaf stage in cereal crops) at a rate of 20 kg per hectare, corresponding to an application rate of 2.0 kg per hectare of triallate and an application rate of 2.80 kg per hectare of methabenzthiazu ron. Pre-emergence application of this granular formulation gave better control of weeds than early post-emergence application, but satisfactory control ofAvena fatua, where weed control of at least 90%, and preferably 95%, is necessary, was only achieved by the application of this granular formulation at a rate of 25 to 30 kg per hectare, corresponding to 2.5 to 3.0 kg per hectare of triallate and 3.5 to 4.2 kg per hectare of methabenzthiazuron.As with the granular formulation containing triallate and neburon described in (1) above, there was no observable additive interaction between the two herbicides triallate and methabenzthiazuron and application rates of both herbicides equal to or greater than those normally recommended for each herbicide when used alone, were required to give satisfactory control of a wide spectrum of grass and broad-leafed weeds.

(3) A granular formulation containing triallate (6%) and metoxuron [N' - (3 - chloro - 4 - methoxy phenyl) - N,N - dimethyiurea; 14% wlw] is described by Madelon metal, ibid. This granular formulation was applied post-emergence at a rate of 20 kg per hectare, corresponding to 1.2 kg per hectare of triallate and 2.8 kg per hectare of metoxuron. Use of this granular formulation is stated to give a 40% reduction in the application rate of triallate and a 30% reduction in the application rate of metoxuron required to control Avena fatua, which Madelonet al, ibid page 888, describe as representing an additive herbicidal effect between trial late and metoxuron.However, the results quoted by Madelon etna!, ibid, page 889, clearly show that, in order to obtain a satisfactory high level of control of Avena fatua, which is at least 90% and preferably 95%, application rates of 1.5 kg per hectare oftriallate and 3.5 kg per hectare of metoxuron are required, which represents only a 25% reduction in the normally required application rate of triallate and a 12.5% reduction in the normally required rate of metoxuron. These findings are confirmed by Huguet, P., Malbrunot, P. and Ranat, G., Compte Rendu de la 9, Conference du COLUMA (1977), pages 870-879. The interaction between triallate and metoxuron onAvena fatua is, at best, only slightly additive and the herbicidal effects of triallate and metoxuron appear, in fact, to be independent.Furthermore, this granular formulation of triallate and metoxuron is restricted in its flexibility in respect of the necessary timing of its application since it must be applied post-emergence.

Accordingly, these published studies on the use of combinations of triallate and herbicides of the phenylurea type teach that the herbicide compo nents of such combinations, i.e. the triallate and the phenylurea herbicide, exert their herbicidal effect largely, if not entirely, independently and that virtu ally the full application rate which is normally recommended when each of triallate and the phenylurea herbicide is used separately, is required when such combinations of triallate and herbicides of the phenylurea type are used, in orderto give the high level of weed control, i.e. at least 90%, and pref erably 95%, which is required, in particular, for Avena fatua in orderto reduce to acceptable levels the return of seeds from surviving plants to the soil and subsequent reinfestation.Independent activity and lack of additive interaction as herbicides would be expected from the known different modes of activity of triallate and herbicides of the phenylurea type. Furthermore these studies suggest that combinations of triallate and isoproturon would be expected to be unsatisfactory both in terms of the control of weeds and in flexibility of timing of application.

As a result of research and experimentation, it has surprisingly been found that the associated use of triallate and isoproturon as herbicides has a powerful additive interaction, particularly onAvena fatua and Alopecurus myosuroides, which provides a method for controlling the growth of both grass weeds and a wide spectrum of broad-leafed weeds reliably by both pre- and post-emergence application, thereby providing the required flexibility in respect of timing of application of the herbicides.

The additive nature of the herbicidal activity exerted bytriallate and isoproturon when used in association is such as to allow a reduction of at least 40% and up to 50% of the application rates of both triallate and isoproturon required for satisfactory weed control, in comparison with the application rates normally required when triallate and isoproturon are used alone, thereby achieving a higher level of weed control and wider spectrum of weeds controlled at given application rates of triallate and isoproturon in association, and improved crop selectivity.It has surprisingly been found that the use of isoproturon in association with triallate in the ratios by weight of 2.5:1 to 1:2.5 respectively, and preferably in the ratio of 1:1 by weight, and at the application rates of 1.0 to 2.5 kg per hectare each of isoproturon and triallate, and more especially 1.25 to 1.75 kg per hectare each of isoproturon and triallate, provides a method for controlling a wide spectrum of grass and broad-leafed weeds at a locus of weed infestation, e.g. in arable crops, particularly wheat and barley, by pre- or post-emergence application and this method forms a feature of the present invention.The spectrum of weed control, flexibility of timing of application and persistence and reliability of weed control provided bythis new method according to the present invention cannot be achieved by either isoproturon ortriallate when either compound is used alone and effective weed control is achieved by the use of lower application rates of isoproturon and triallate than wou Id be required by the use of either isoproturon ortriallate alone, thereby reducing the risk of damage to the crop. More especially, the method according to the present invention gives a high degree of control ofAvena fatua and Alopecurus myosuroides, with which weed control of at least 90%, and preferably 95%, is necessary to reduce to acceptable levels the return of seeds from surviving plants to the soil. To obtain this level of simultaneous control of bothAvena fatua and Alopecurus myosuroides with either isoproturon or triall ate alone would necessitate the use of high dose rates, thus reducing crop selectivity and increasing the risk of damage to the crop.

According to a further feature of the present invention, there is provided a method for the control of the growth of grass weeds, e.g. Avena fatua, Avena ludoviciana, Alopecurus m yosuroides, Apera spica venti, Poa annua, Poa trivialis and Bromus sterilis, and broad-leafed weeds, e.g.Aphanes arvensis, Anthem is arvensis, Anthemis cotula, Chenopodium album, Chrysanthemum segetum, Fumaria officionalis, Matricaria inodora, Papaverrhoeas, Polygonum aviculare, Polygonum persica, Polygonum lapathifolium, Stellaria media, Spergula arvensis and Veronica persica, by pre- or post emergence application to a locus of weed infestation which is an area used, orto be used, for growing crops of cereal crops, in particular winter wheat, spring wheat, winter barley, spring barley and rye, and field beans, or by post-emergence application to a locus of weed infestation which is an area used for growing a crop of winter sown oilseed rape, in the ratios of isoproturon to triallate by weight of 2.5:1 to 1:2.5 respectively, and preferably in the ratio of 1::1 by weight, and at the application rates of 1.0 to 2.5 kg per hectare each of isoproturon and triallate, and more especially 1.25 to 1.75 kg per hectare each of isoproturon and triallate. (By the term 'locus of weed infestation' is meant an area of soil, e.g. a cropgrowing area, in which weeds have emerged or are expected to emerge).

Application to autumn-sown crops of cerea Is, e.g.

winter wheat and winter barley, and field beans gives particularly good results. Good control of weeds in spring-sown cereals may also be produced by application in the previous autumn, when the application is followed by prolonged periods of extreme cold, e.g. when the soil temperature remains at or below 0 C for three to five months, during the intervening winter.

In carrying out the method according to the present invention, isoproturon and triallate may be applied simultaneously or separately in the rations by weight and at the application rates hereinbefore indicated, using conventional formulations, e.g.

emulsions of triallate obtained by the dilution of emulsion concentrates with water and granular formulations of trial late, and suspensions of isoproturon obtained by the dilution of wettable powders and aqueous suspension concentrates of isoproturon with water, and granular formulations of isoproturon, or in granularformulations containing both isoproturon and triallate.

The available flowable suspension formulations of isoproturon and granular formulations of triallate are not normally such as to permit simultaneous application, for example by mixing the two formulations to give a tank-mix which may then be applied to a locus of weed infestation, thereby necessitating application of the two herbicides in separate operations, and the same is the case with granular formulations of isoproturon and emulsion concentrates of triallate. Hitherto, it has been considered that, in order to obtain good control ofAvena fatua, it is necessary to incorporate emulsions of triallate into the soil at, or very shortly after, the time of application.It has now surprisingly been found that tankmixes prepared from emulsion concentrates of triallate with wettable powder or aqueous suspension concentrates of isoproturon, give excellent control of Avena fatua when applied underwinterconditions without incorporation into the soil. It is believed that this is due to the reduced volatility of triallate at low temperatures and/or adsorption of the triallate onto the particles of isoproturon. Similarly, the use of emulsion suspension concentrate formulations and emulsifiable suspension concentrate formulations containing both triallate and isoproturon gives good control ofAvena fatua when applied under winter conditions without incorporation into the soil.However for greater flexibility, when simultaneous application of isoproturon and triallate is desired, it is preferable to use granular formulations containing isoproturon and granular formulations containing triallate which may be mixed together as a tank-mix, or more especially to use granules containing both isoproturon and triallate. Granular formulations containing both isoproturon and triallate in the ratios of isoproturon to triallate by weight of 2.5:1 to 1:2.5 respectively, and more especially in the ratio of 1:1 by weight and the use of such granular formulations at application rates of 1.0 to 2.5 kg per hectare each of isoproturon and triallate, and more especially 1.25 to 1.75 kg per hectare each of isoproturon and triallate to control the growth of weeds at a locus of weed infestation as hereinbefore described, form preferred features of the present invention.

According to a further preferred feature of the present invention, isoproturon is used in association with triallate in the ratios of isoproturon to trial late by weight of 2.5:1 to 1:2.5 respectively, and more especially in the ratio of 1:1 by weight and at application rates of 1.0 to 2.5 kg per hectare of each of isoproturon and triallate, and more especially 1.25 to 1.75 kg per hectare of each of isoproturon and triallate to control the growth of weeds, for example those weeds hereinbefore indicated, at a locus of weed infestation which is an area used, orto be used, for growing crops of wheat or barley:: (a) by application and incorporation into the soil before sowing of the crop of an emulsion of triallate (obtained by the dilution of an emulsion concentrate with water), followed by the pre- or post-emergence application of an aqueous suspension of isoproturon (obtained by the dilution with water of a wettable powder or aqueous suspension concentrate) or of granules containing isoproturon, (b) by the pre- or post-emergence application and incorporation into the soil before the sowing of the crop of granules containing triallate followed by the pre- or post-emergence application of an aqueous suspension of isoproturon (obtained by the dilution with water of a wettable powder or aqueous suspension concentrate) or of granules containing isoproturon, (c) by simultaneous pre- or post-emergence application under winter conditions without incorporation into the soil of liquid formulations of isoproturon and triallate, obtained by the dilution with water of tank-mixes of wettable powder or aqueous suspension concentrates of isoproturon and emulsion concentrates of triallate or emulsion suspension concentrates or emulsifiable suspension concentrates containing both isoproturon and triallate, (d) by the simultaneous pre- or post-emergence application of granules containing isoproturon and granules containing triallate in the form of a tank mix, or, (e) preferably, the pre- or post-emergence application of granularformulations containing both isop roturon and triallate.

Compositions suitable for use in the method of the present invention comprise isoproturon or triallate in association with, and preferably homogeneously dispersed in, one or more compatible herbicidallyacceptable diluents or carriers (i.e. diluents or carriers of the type generally accepted in the art as being suitable for use in herbicidal compositions and which are compatible with isoproturon or triallate).

The term "homogeneously dispersed" is used to include compositions in which isoproturon or trial- late are dissolved in the other components. The term "herbicidal compositions" is used in a broad sense to include not only compositions which are ready for use as herbicides but also concentrates which must be diluted before use. Preferably, the compositions contain from 0.05 to 90% by weight of isoproturon or triallate.

The herbicidal compositions may contain both a diluent or carrier and a surface-active (e.g. wetting, dispersing, or emulsifying) agent. Surface-active agents which may be present in the herbicidal compositions may be of the ionic or non-ionic types, for example sulphoricinoleates, quaternary ammonium derivatives, products based on condensates of ethylene oxide with nonyl- or octyl-phenols, or carboxylic acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxy groups by condensation with ethylene oxide, alkali and alkaline earth metal salts ofsulphuric acid esters and sulphonic acids such as dinonyl- and dioctyl-sodium sulphonosuccinates and alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates.Examples of suitable solid diluents or carriers are aluminium silicate, talc, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, absorbent carbon black and clays such as kaolin and bentonite. The solid compositions (which may take the form of dusts, granules or wettable powders) are preferably prepared by grinding isoproturon ortriallate with solid diluents or by impregnating the solid diluents or carriers with solutions of isoproturon ortriallate in solvents and, if necessary, grinding the products so as to obtain powders. Granular formulations may be prepared by absorbing isoproturon ortriallate (dissolved in solvents) onto the solid diluents or carriers in granular form or by granulating compositions in powder form obtained as described above.Solid herbicidal compositions, particularly wettable powders, may contain wetting or dispersing agents (for example of the types described above), which may also, when solid, serve as diluents or carriers.

Liquid compositions may take the form of aqueous, organic or aqueous-organic solutions, suspensions and emulsions which may incorporate a surface-active agent. Suitable liquid diluents for incorporation in the liquid compositions include water, acetophenone, cyclohexanone, isophorone, toluene, xylene and mineral, animal and vegetable oils (and mixtures of these diluents). Surface-active agents, which may be present in the liquid compositions, may be ionic or non-ionic (for example of the types described above) and may, when liquid, also serve as diluents or carriers. Wettable powders and liquid compositions in the form of concentrates may be diluted with water or other suitable diluents, for example mineral or vegetable oils, particularly in the case of liquid concentrates in which the diluent or carrier is an oil, to give compositions ready for use.

When desired, liquid compositions of isoproturon or triallate may be used in the form of self-emulsifying concentrates containing the active substances dissolved in the emulsifying agents or in solvents containing emulsifying agents compatible with the active substance, the simple addition of water to such concentrates producing compositions ready for use. Suitably, the herbicidal compositions may comprise from 0.05% to 15% of surface active agent.

The herbicidal compositions may also contain, if desired, conventional adjuvants such as adhesives, protective colloids, thickeners, penetrating agents, stabilisers, anti-freezes, sequestering agents, anticaking agents, colouring agents and corrosion inhibitors. These adjuvants may also serve as carriers or diluents.

Compositions suitable for use in the method of the present invention also include compositions which comprise both isoproturon and triallate as herein be fore described in respect of compositions suitable for use in the method of the present invention which comprise isoproturon ortriallate, in the form of liquid emulsion suspension concentrates and liquid emulsifiable suspension concentrates comprising both isoproturon and triallate, which may be diluted with water to give compositions ready for use, and granular formulations which comprise both isoproturon and triallate.

Liquid emulsion suspension concentrates comprising triallate dissolved in organic solvents, e.g.

hydrocarbon solvents, emulsified in aqueous suspensions of micronised isoproturon particles, liquid emulsifiable suspension concentrates comprising solutions of triallate in organic solvents, e.g. hydrocarbon solvents, in which are suspended micronised isoproturon particles, and, more especially, granular formulations containing both isoproturon and triallate, the ratios of isoproturon to triallate by weight in the aforesaid emulsion suspension concentrates, emulsifiable suspension concentrates and granular formulations being 2.5:1 to 1 :2.5, and more especially 1:1, respectively, form preferred features of the present invention. Liquid emulsion suspension concentrates according to the present invention containing both isoproturon and triailate preferably comprise a combined total of from 10% to 70% weight/volume (wiz) of isoproturon and triallate, from 2% to 10%wlvofsurface-active agent, from 0.1% to 5% w/v of thickener, from 15% to 87.9% by volume of organic solvent and from 0% to 60% by volume of water, and may be prepared by mixing these ingredients.Liquid emulsifiable suspension concentrates according to the present invention containing both isoproturon and triallate preferably comprise a combined total of from 10% to 70% w/v of isoproturon and triallate, from 5% to 15% of surface-active agent, from 0.1% to 5% w/v of thick ener and from 10% to 84.9% by volume of organic solvent and may be prepared by mixing these ingre dients.Granular formulations according to the pres ent invention containing both isoproturon and trial late preferably comprise a combined total of from 2% to 20% byweightofisoproturon and triallate, from 0.1% to 10% by weight of surface-active agent and from 70% to 97.9% by weight of granular carrier and may be prepared by granulating powders com prising these ingredients or, more conveniently, by absorbing solutions of isoproturon, triallate and surface-active agent in suitable solvents, e.g.

dimethylformamide, onto the granular carrier and, if desired, removing the solvents, or, more especially, by incorporating micronised isoproturon particles, triallate and surface-active agent, as hereinafter described in respect of the preferred granular formulations according to the present invention.

According to a further feature of the present invention, there are provided preferred granular formulations containing both isoproturon and triallate which have been found by research and experimentation to have particularly advantageous properties, for example when used in the method of controlling the growth of weeds according to the present invention.

The preferred granular formulations according to the present invention (hereinafter referred to as the 'preferred granules') not only permit the simultaneous appllcation of isoproturon and triallate to a locus of weed infestation in a single operation, but also afford the additional advantage of allowing the pre paration of granular formulatlons containing greater concentrations of isoproturon than is conveniently possible by absorbing solutions of isoproturon onto a granular carrier, the maximum amount of isop roturon which can be incorporated onto a granular carrier by means of a solvent solution being, in practice, about 3% wiw. These preferred granules allow the release of isoproturon without any delay being produced in the release of triallate, and gives enhanced control of the important weed species A vena fatua andA/opecusus rnyosvrcides.

The preferred granules contain isoproturon and trial late in the ratios by weight of 2.5:1 to 1:2.5 respectively, and more especially in the ratio of 1:1 by weight, and a combined total of from 2% to 20% by weight of isoproturon, in the form of micronised particles, and triallate and, in order to achieve particularly satisfactory release of the two herbicides, have a diameter of from 150 to 1000 microns. The preferred granules according to the present invention may be of the compounded type, i.e. granules in which the micronised particles of isoproturon and the triallate are incorporated into the body of the granule, or, as is preferred, of the core type i.e.

granules consisting of a granule core into which the trial late is incorporated and to the surface of which the micronised particles of isoproturon adhere, and having an overall diameter of 150 to 1000 microns.

The preferred compounded granules and the granular cores of the preferred core granules according to the present invention may be formed from inert carriers of the types customarily used in the preparation of granular formulations used in agriculture and which are absorbent and permeable to triallate and triallate-containing solutions. Suitable inert carriers include clays. The preferred inert carrier according to the present invention is sepiolite, which is a clay consisting predominantly of magnesium and aluminium silicates. Mineral clays with similar absorptive properties to sepiolite, for example montmorillonite, attapulgite and diatomite, are also suitable.

When incorporated into the preferred compounded granules according to the present invention, the micronised isoproturon particles are from 1 micron to 40 microns in diameter, the use of parti cles of diameter greater than 40 microns being undesirable, since an unsatisfactory rate of release of isoproturon may result.

When incorporated into the preferred core granules according to the present invention, in which the particles of isoproturon adhere to the surface of the granule core, satisfactory release of isoproturon from the granules and satisfactory resistance to removal of isoproturon by mechanical abrasion during manufacture, storage and transportation, is achieved by the use of micronised isoproturon particles predominantly less than 10 microns in diameter and preferably less than 5 microns in diameter.More especially, the micronised isoproturon incorporated into the preferred core granules according to the present invention should not con tain in excess of a 1% of particles of 10 microns or greater diameter, in excess of 20% of particles of 5 microns or greater in diameter and in excess of 65% of particles of 2.5 microns or greater in diameter, and preferably at least 90% of the particles should have a particle size of 1 micron diameter or greater.

The preferred granules according to the present invention may contain, in addition to an inert carrier, surface-active (e.g. wetting, dispersing or emulsifying; agents. Surface-active agents which may be present in granular formulations according to the present invention may be of the ionic or non-ionic types, for example sulphoricinoieates, quaternary ammonium derivatives, carboxylic acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxy groups with ethylene oxide, alkali and alkaline earth metal salts of sulphune and sulphonic acids such as dinonyland dioctyl-sodium sulpho-succinates, alkali and alkaline earth metal salts of high molecular weight sulphonic acid derivatives such as sodium and calcium lignosulphonates or, preferably, products based on condensates of ethylene oxide with nonylor octyl-phenols. Incorporation of surface-active agents into the granular formulations according to the present invention facilitates both the preparation of the granules and the release of isoproturon from the granules when in use for herbicidal purposes.

Preferably, the preferred granules according to the present invention contain from 0.1% to 10% by weight of surface-active agent.

The preferred granules according to the present invention, and more especially the preferred core granules, may, if desired, contain from 0.01% to 5% weight/weight (w/w) of adhesives or 'stickers', for example cellulosic or xanthene gums, paraffin waxes, resins, polyisobutenes, polyvinyl alcohol or vinyl acetate, which assist, in particular, adherence of the isoproturon particles to the inert carrier.

The preferred granules according to the present invention in the form of compounded granules may be prepared by intimately mixing the micronised isoproturon and triallate and, if desired, surface active agent, with the inert carrier, e.g. a clay, for example sepiolite, in powder form, if necessary in the presence of a suitable liquid, and then granuiat ing the powder blend thus obtained and, if neces sary, drying the granules thus obtained, or by inti mately mixing the micronised isoproturon and, if desired, surface-active agent, with the inert carrier, e.g. a clay, for example sepiolite, in powder form, if necessary in the presence of a suitable liquid, granulating the powder blend thus obtained and, if necessary, drying the granules thus obtained, and then treating the isoproturon - containing granules with a solution of triallate in a suitable liquid to absorb the triallate into the granules and, if necessary, drying the granules thus obtained.

Preferred granules according to the present invention in the form of core granules, which form a particularly preferred feature of the present invention, may be prepared by suspending the micronised isoproturon in a solution of triallate and, if desired, surface-active agent, in a suitable liquid and apply ing uniformly the suspension thus obtained to granule cores of the inert carrier, e.g. a clay, for example sepiolite, in a blender, whereby the triallite and, if present, surface-active agent, are absorbed into the granule core and the micronised isoproturon particles adhere to the surface of the granule core and, if necessary, drying the granules thus obtained.

If desired, adhesives may be incorporated during the preparation of the preferred granules.

Suitable liquids which may be used in the prepara tion of the preferred granules according to the pres ent invention are liquids in which triallite has a solu bility of at least 30% w/v (weight/volume) and pref erably of 40% w/v or greater, but in which isoprotu ron has a solubility not greater than, and preferably less than, 5% wlv, and include aliphatic and aromatic hydrocarbons, ketones, alcohols, ethers, dimethyl sulphoxide and chlorinated hydrocarbons. Suitable liquids may be volatile or non-volatile and the use of volatile liquids facilitates removal of excess liquid after preparation of the preferred granules.How ever, the preferred granules may be allowed to con tain from 1% to 25% w/w of suitable liquids, the pre sence of which serves to facilitate, if desired, the release of isoproturon and, more especially, triallate from the preferred granules at the time of use to control the growth of weeds, more especially when surface-active agents are incorporated in the prefer red granules. For this purpose, the use of suitable liquids of relatively low volatility is preferred.It is to be understood that the term 'drying', when used in the context of the preparation of the preferred granules, refers essentially to the removal of any surplus of suitable liquids from the surface of the preferred granules as a final stage in their prepara 5 tion and does not necessarily indicate the substantially-total removal of the suitable liquid used in the preparation of the preferred granules.

Powder blends and inert carriers in powder form may be granulated by conventional techniques, e.g.

extrusion and granulation, compaction and granulation, pan granulation, ribbon blender granulation, fluid bed granulation and granulation by prilling.

The following Examples illustrate the preparation of formulations suitable for use in the method of controlling the growth of weeds according to the present invention.

EXAMPLE 1 Granules containing both isoproturon and triallate containing: Isoproturon 3% w/w Triallate 3%wiw Ethylan BCP (a nonylphenoll ethylene oxide condensate containing 9 to 10 moles of ethylene oxide per mole of nonylphenol) 0.36% w/w Dimethylformamide 23.64% w/w Sepitol 30/60 granule cores (sepiolite granules of which 90% have a diameteroffrom 250 to 500 microns) to 100% by weight were prepared by dissolving the isoproturon, triallate and Ethylan BCP in the dimethylformamide at 20"C with stirring and then spraying the resultant solution onto the granule cores in a drum blender.

The granules were then sieved to remove agglomerates, to give granules utilised in Experiment 1 described herein and which may be applied at a rate of 50 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of wheat, after sowing the crop, to control by preemergence application the growth of annual grass weeds and broad-leafed weeds as hereinbefore described.

The following Examples 2 to 7 illustrate the preparation of preferred granules according to the present invention.

EXAMPLE2 Core granules containing 6% by weight each of isoproturon and triallate were prepared by: Step A Mixing together: (1) Triallate (technical grade containing 90% by weight of triallate) (2.38 kg) (2) Ethylan BCP (0.26 kg) (3) High Flash Naphtha CW (a high boiling point petroleum fraction) (5.82 kg) Step B Slowly adding micronised isoproturon (technical grade containing 95% by weight of isoproturon; particle size 99% less than 10 microns in diame ter. 80% less than 5 microns in diameter, 35% less than 2.5 microns in diameter, obtained by air-jet mil ling) (2.26 kg) with stirring to the solution obtained ih Step A and continuing mixing until a smooth slurry was obtained.

Step C Sieving the slurry obtained in Step B through a 60-mesh British Standard sieve and spraying at a pressure of 32 pounds per square inch through a Teejet 8002 fan-jet delivering approximately 600 ml of slurry per minute at an angle of spray pattern of 600 to 80" on to Sepitol 30/60 granule cores (sepiolite granules of which 90% have a diameter of from 250 to 500 microns) (25 kg) in a Nauta (cone blender) mixer with continuous mixing. On completion of spraying and a further brief period of mixing, the granules were sieved through a 12-mesh British Standard sieve to remove agglomerates.

There was thus obtained 35.72 kg of core granules containing 6% w/w of both isoproturon and triallate utilised in Experiment 2 described herein and which may be applied art a rate of 25 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of wheat, after sowing of the crop, to control by pre-emergence application the growth of annual grass weeds and broad-leafed weeds as hereinbefore described.

EXAMPLE 3 By proceeding as described in Example 2 but using 2.78 kg of triallate (technical grade containing 90% by weight of triallate), 0.3 kg of Ethylan BCP, 9.29 kg of High Flash Naphtha CW, 2.63 kg of isoproturon (technical grade containing 95% by weight of isoproturon containing the percentage of particle sizes specified in respect of the isoproturon used in Example 2) and 35 kg of Sepitol 30/60 core granules there was obtained 50 kg of core granules containing 5% w/w of both isoproturon and triallate utilised in Experiment 2 described herein and which may be applied at a rate of 25 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of wheat, after sowing of the crop, to control by pre-emergence application the growth of annual grass weeds and broad-leafed weeds as hereinbefore described.

EXAMPLE 4 By proceeding as described in Example 2 using the appropriate amounts of triallate and isoproturon, there were obtained core granules containing 4% wlw of isoproturon and 10% w/w of triallate, which may be applied at a rate of 25 keg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of winter wheat, after sowing of the crop, to control by pre-ernergence application the growth of Avena fatua, Alopecurus myosuroides, Veronica persica and Matricaria inodora.

EXAMPLE 5 By proceeding as described in Example 2 using the appropriate amounts of triallate and isoproturon, there were obtained core granules containing 10%w/w of isoproturon and 4% w/w of triallate, which may be applied at a rate of 25 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of winter wheat, after sowing of the crop, to control by pre-emergence application the growth ofAvena fatua, Alopecurus myosuroides, Veronica persica, Matricaria inodora and Stellaria media.

EXAMPLE 6 By proceeding as described in Example 2 using the appropriate amounts of tdallate and isoproturon, there were obtained core granules containing 1% w/w of isoproturon and 1% w/w of triallate, which may be applied art a rate of 150 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of winter wheat, after sowing of the crop, to control by pre-emergence application the growth of Avena fatua, Alopecurus myosuroides, Veronica persica, Matricaria inodora and Stellaria media.

EXAMPLE 7 By proceeding as described in Example 2 using the appropriate amounts of triallate and isoproturon, there were prepared core granules containing 10% w/w of isoproturon and 10% w/w of triallate, which may be applied at a rate of 15 kg of granules per hectare to a locus of weed infestation which is an area used to grow a crop of winter barley, after sowing of the crop, to control the growth by preemergence application ofAvena fatua, Alopecurus myosuroides, Veronica persica, Matricaria inodora and Stellaria media.

EXAMPLE 8 A liquid emulsion suspension concentrate containing: lsoprotu ron (micronised) 25% w/v Triallate 25% w/v Ethylan BCP 10%w/v High Flash Naphtha CW 25% volumelvolume (v/v) Ethylene glycol 5% v/v Rhodigel 23 (polysaccharide xanthan gum thickener) 0.2% w/v Water to 100% by volume was obtained by preparing a solution of the triallate and 80% of the Ethylan BCP in the High Flash Naphtha CW and a suspension of the micronised isoproturon, 20% of the Ethylan BCP, the ethylene giycol, the Rhodigel 23 and water, mixing the solution and suspension with adequate stirring and adding water to 100% by volume with stirring, to give a smooth cream, which may be diluted with water and applied without incorporation into the soil at an application rate of 5 to 7 litres of emulsion suspension concentrate in 400 litres of spray fluid per hectare to control the growth of Avena fatua, Alopecurus myosuroides, and broad-leafed weeds, e.g. those species hereinbefore described, by postemergence application in an emerged crop of winter wheat.

EXAMPLE 9 A liquid emulsifiable suspension concentrate containing: Isoproturon (micronised) 30% w/v Triallate 30% w/v Ethylan BCP 4%w/v Arylan CA (calcium dodecyl benzene suphonate) 3%wlv Ethylhydroxyethylcellulose (thickener) 1%wiv High Flash Naptha CW to 100% by volume was obtained by preparing a solution of the triallate, Ethylan BCP and Arylan CA in High Flash Naptha CW, dissolving the cellulose thickener with maceration in this solution, suspending the micronised isoproturon in the solution thus obtained by stirring and adding High Flash Naphtha CWto 100% by vol ume with stirring.The emulsifiable suspension con centrate thus obtained may be diluted with water and applied without incorporation into the soil at a rate of 5 litres of emulsifiable suspension concen trate in 300 litres of spray fluid per hectare to a locus of weed infestation which is an area used to grow a crop of winter barley, after sowing of the crop, to control by pre-emergence application the growth of annual grass weeds and broad-leafed weeds, e.g.

those species hereinbefore described.

EXAMPLE 10 By proceeding as described in Example 8 using the appropriate amounts of micronised isoproturon and triallate, a liquid emulsion suspension concentrate was prepared containing 10% w/v of isoproturon and 25% w/v of triallate, which may be diluted with water and applied without incorporation into the soil at an application rate of 10 litres of emulsion suspension concentrate in 400 litres of spray fluid per hectare to control the growth ofAvena fatua, Alopecurus myosuroides and broad-leafed weeds, e.g. those species hereinbefore described, by post-emergence application in an emerged crop of winter wheat.

EXAMPLE 11 By proceeding as described in Example 8 using the appropriate amounts of micronised isoproturon and triallate, a liquid emulsion concentrate was prepared containing 25% w/v of isoproturon and 10% wiv of triallate which may be diluted with water and applied without incorporation into the soil at a rate of 10 litres of emulsion suspension concentrate in 400 litres of spray fluid per hectare to a locus of weed infestation which is an area used to grow a crop of winter wheat, after sowing of the crop, to control by pre-emergence application the growth ofAvena fatua, Alopecurus myosuroides, Veronica persica, Matricaria inodora and Stellaria media.

EXAMPLE 12 By proceeding as described in Example 9 using the appropriate amounts of m icronised isoproturon and triallate, a liquid emulsifiable suspension concentrate was prepared containing 10% w/v of isoproturon and 25% w/v of triallate, which may be diluted with water and applied without incorporation in the soil at a rate of 10 litres of emulsifiable suspension concentrate in 400 litres of spray fluid per hectare to a locus of weed infestation which is an area used to grow a crop of winter wheat, after sowing of the crop, to control by pre-emergence application the growth ofAvena fatua, Alopecurus myosuroides, Veronica persica and Matricaria inodora.

EXAMPLE 13 By proceeding as described in Example 9 using the appropriate amounts of micronised isoproturon and triallate, a liquid emulsifiable suspension concentrate was prepared containing 10% w/v of isoproturon and 25% wlv oftriallate, which may be diluted with water and applied without incorporation into the soil at a rate of 10 litres of emulsifiable suspension concentrate in 400 litres of spray fluid per hectare to control the growth of A vena fatua, Alopecurus myosuroides and broad-leafed weeds, e.g. those species herein before described, by post emergence application in an emerged crop of winter wheat.

The method of controlling the growth of weeds according to the present invention is demonstrated in the following experiments.

EXPERIMENT 1 Isoproturon and trial late were applied simultaneously, in the form of granules containing both isoproturon and triallate, in comparison with applications of isoproturon ortriallate, pre- or postemergence to field grown crops of winter wheat and barley in the sout-east of England and the East Anglia district of England. The applications were made at times after sowing of the crop from pre-emergence to the 3-leaf stage of grass weeds and the 4-to 6-leaf stage of broad-leafed weeds. (Applications to Papaverrhoeas were made at the pre-emergence stage only.

The formulations used in this experiment were: (1) granules containing both 3% w/w (weight/weight) of isoproturon and 3% w/w of triallate, prepared as described in Example 1. These granules were applied at a rate of 50 kg of granules per hectare, corresponding to 1.5 kg per hectare each of isoproturon and triallate, (2) a commercially available 50% weight/volume aqueous suspension concentrate of isoproturon, which was applied, after dilution with water, at a rate of 5 litres of concentrate in 293.3 litres of spray fluid per hectare, corresponding to 2.5 kg per hectare of isoproturon, (3) commercially available granules containing 10% w/w of triallate. These granules were applied at a rate of 27.5 kg of granules per hectare, corresponding to 2.75 kg per hectare of triallate.

Granular formulations were applied uniformly by means of a motorised granular applicator. Sprays of aqueous suspensions of isoproturon were applied by means of a small-plot motorised sprayer using 6 jets (8002 teejets) at a pressure of 2.1 bars and delivering a volume rate equivalent to 293.3 litres of spray fluid per hectare.

For each treatment, three replicated plots, each 12 metres long and 3.5 metres wide, were used and untreated plots were kept as controls.

Three or four months after treatment, the numbers of weeds occurring in 1/2 square metre quadrats (2 or 3 per plot) were recorded and the percentage weed control of individual weed species and of all the weeds (total weeds) obtained in treated plots was determined in comparison with untreated control plots, by the following formula: Percentage weed control = X-Y x 100 where X is the number of weeds in untreated plots and Y is the number of weeds in treated plots.

The results obtained are set out in the following Table 1.

TABLE 1

Treatment Application Percentage weed control rate (kglhectare) isoproturon Avena Alopecurus Poa Stellaria Papaver Matricaria Veronica Total and/or fatua myosur ua media rhoeas inodora persica Weeds tria late triallate Granules containing 1.5 (i) both (i) + 97 100 100 99 100 i 100 99 98 isoproturon / 1.5 (ii) and (ii) triallate Isoproturon aqueous 2.5 85 96 100 99 100 100 65 90 suspension Triallate granules 2.75 85 85 94 27 74 37 93 70 Number of sites 7 9 7 1 I 3 8 1 3 5 5 These results show that the use of low application rates of isoproturon and triallate in assication gives much better control of a wide spectrum of weeds than the use of higher application rates of isoproturon and triallate alone.

The method of controlling the growth of weeds by application of preferred granules according to the present invention is demonstrated in the following experiment.

EXPERIMENT2 Isoproturan and trial late were applied simultane ously, in the form of granules containing both isop roturon and triallate, in comparison with applications of isoproturon ortriallate, pre- or postemergence to field grown crops of winter wheat and barley in the south-east of England and the East Anglia district of England. The applications were made at times after the sowing of the crop from pre-emergence to the 3-leaf stage of grass weeds and the 4-to 6-leaf stage of broad-leafed weeds. (Applications to Papaverrhoeas were made at the pre-emergence stage only).

The formulations used in this experiment were:- (1) granules containing (a) both 6% w/w (weight/weight) of isoproturon and 6% w/w of triallate, prepared as described in Example 2 and (b) both 5% w/w of isoproturon and 5% w/w of triallate, prepared as described in Example 3.These granules were applied at a rate of 25 kg of granules per hectare, corresponding to 1.5 kg per hectare each of isoproturon and triallate and 1.25 kg per hectare each of isoproturon and triallate, respectively, (2) a commercially available 50% weight/volume aqueous suspension concentrate of isoproturon, which was applied, after dilution with water, at a rate of 5 litres of concentrate in 293.3 litres of spray fluid per hectare, corresponding to 2.5 kg per hectare of isoproturon, (3) commercially available granules containing 10% w/w of triallate. These granules were applied at a rate of 27.5 kg of granules per hectare, correspond ing to 2.75 kg per hectare oftriallate.

Granular formulations were applied uniformly by means of a motorised granular applicator. Sprays of aqueous suspensions of isoproturon were applied by means of a small-plot motorised sprayer using 6 jets !8002 teejets) at a pressure of 2.1 bars and deliv ering a volume rate equivalent to 293.3 litres of spray fluid per hectare.

For each treatment, three replicated plots, each 12 metres long and 3.5 metres wide, were used and untreated plots were kept as controls.

Three or four months after treatment, the number of weeds occurring in 1/2 square metre quadrats (2 or3 per plot) were recorded and the percentage weed control of individual weed species and of all the weeds (total weeds) obtained in treated plots was determined in comparison with untreated control plots, by the following formula: Percentage weed control = X X Y x 100 where X is the number of weeds in untreated plots and Y is the number of weeds in treated plots.

The results obtained are set out in the following Table 2.

TABLE2

Treatment Application Percentage weed control rate 0 (kgthectare) isoproturon Avena Avena Alopecurus Poa Stellaria Papaver j Matricaria Veronica Tota[ andlor fatua myosuroides annua media rhoeas inodora persica Weeds triallate Granules 1.5(i) containing + 99.5 99.5 100 98 100 100 100 99 both (i) 1.5(ii) 1.25 (i) and (ii) + 99 99 100 96 100 100 98 96 triallate 1.25 (ii) Isoproturon aqueous 2.5 85 96 100 99 j 100 100 65 90 suspension Triallate granules 2.75 85 85 94 27 74 37 93 1 70 Number of sites 1 7 9 3 8 1 3 5 - These results showthatthe use of low application rates of isoproturon and triallate in the preferred granules gives much better control of a wide spectrum of weeds than the use of higher application rates of isoproturon and trial late alone.

EXPERIMENT 3 Isoproturon and triallate were applied simultane ously, in the form of a tank-mix of triallate emulsion and isoproturon suspension in comparison with applications of isoproturon or triallate alone, pre- or post-emergence to field grown crops of winter wheat and barley in the East Anglia district of England. The applications were made at times after the sowing of the crop from pre-emergence to postemergence of grass weeds and broad-leafed weeds.

The formulations used in this experiment were: (1) a tank-mix prepared by mixing and diluting with water a commercially available 40% weight/volume emulsifiable concentrate of triallate and a commercially available 50% weightivolume aqueous suspension concentrate of isoproturon.This tank-mix was applied, after dilution with water, at a rate of 3.75 litres oftriallate emulsifiable concentrate and 3.0 litres of isoproturon aqueous suspension concentrate in 340 litres of spray fluid per hectare, corresponding to 1.5 kg per hectare each of isoproturon and triallate, (2) the commercially available 50% weight/volume aqueous suspension concentrate of isoproturon mentioned in (1) immediately above, which was applied, after dilution with water, at a rate of 5 litres of concentrate in 340 litres of spray fluid per hectare, corresponding to 2.5 kg per hectare of isoproturon, (3) commercially available granules containing 10% w/w of triallate. These granules were applied at a rate of 22.5 kg of granules per hectare, corresponding to 2.25 kg per hectare of triallate.

Granular formulations oftriallate were applied uniformly by means of a motorised granular applicator. Sprays of aqueous suspensions of isoproturon alone and the liquid tank-mix of triallate emulsion and isoproturon suspension were applied by means of a small-plot motorised sprayer using 6 jets (8003 teejets) at a pressure of 2.1 bars and delivering a volume rate equivalent to 340 litres of spray fluid per hectare.

For each treatment, three replicated plots, each 10 metres long and 3 metres wide, were used and untreated plots were kept as controls.

Three or four months after treatment, the numbers of weeds occurring in 1/2 square metre quadrats (2 per plot) were recorded and the percentage weed control of individual weed species obtained in treated plots was determined in comparison with untreated control plots, by the following formula:- X - Y Percentage weed control = x 100 where X is the number of weeds in untreated plots and Y is the number of weeds in treated plots.

The results obtained are set out in the following Table 3.

TABLE 3

Treatment Application Percentage weed control rate (kglhectare) isoproturon Avenua Alopecurus Poa Stellaria Palaver Matricaria Veronica andlor fatua myosuroides annua media rhoeas inodora persica triallate Liquid tank-mix containing both (i) isoproturon 1.5(i) and (ii) + 90 97 98 96 100 99 93 triallate 1.5 (ii) lsoprotu ron aqueous 2.5 75 95 93 96 100 100 55 suspension Triallate granules 2.25 76 66 67 31 15 41 93 Number of sites 8 8 4 7 1 8 6 These results show that the use of a low application rate of a liquid tank-mix containing both isoproturon and triallate gives much better control of a wide spectrum of weeds than the use of higher application rates of isoproturon and trillate alone.

CLAIMS 1. A method for the control of the growth of grass weeds and broad-leafed weeds characterised in that the herbicide 3 - (4 - isopropylphenyl) - 1,1 dimethylurea (hereinafter referred to as 'isoprotu- ron') and the herbicide S - 2,3,3 - trichloroallyl diisop ropylthiocarbamate (hereinafter referred to as 'trial late') are applied in association to a locus of weed infestation in the ratios of isoproturon to triallate by weight of 2.5:1 to 1:2.5 respectively and at the appli cation rates of 1.0 to 2.5 kg per hectare each of isop roturon and triallate by pre- or post-emergence application.

2. A method for the control of the growth of grass weeds and broad-leafed weeds according to claim 1 characterised in that isoproturon and triallate are applied in association (i) by pre- or post emergence application to a locus of weed infestation which is an area used, orto be used, for the growing of cereal crops and field beans or (ii) by post emergence application to a locus of weed infestation which is an area used for growing a crop of winter sown oilseed rape.

3. A method for the control of the growth of grass weeds and broad-leafed weeds according to claim 1 or 2 characterised in that the ratio of isop roturon to triallate applied to the locus is 1:1 by weight.

4. A method for the control of the growth of grass weeds and broad-leafed weeds according to claim 1,2 or 3 characterised in that the application rate of isoproturon and trial late to the locus is from 1.25 to 1.75 kg of each compound per hectare.

5. A method according to any one of the preceding claims characterised in that the weeds controlled are one or more ofAvena fatua, Avena ludoviciana, Alopecurus myosuroides, Apera spica-venti, Poa annua, Poa trivialis and Bromus sterilis.

6. A method according to any one of claims 1 to 4 characterised in that the weeds controlled are one or more ofAphanes arvensis, Anthemis arvensis, Anthemis cotula, Chenopodium album, Chrysanthemum segetum, Fumaria officionalis, Matricaria inodora, Papaverrhoeas, Polygon urn aviculare, Polygonum persica, Polygonum lapathifolium, Stellaria media, Spergula arvensis and Veronica persica.

7. A method according to any one of claims 1 to 5 characterised in that the weeds controlled areAvena fatua orAlopecurus myosuroides.

8. A method according to any one of claims 1 to 7 characterised in that the locus of weed infestation is an area used, or to be used, for growing a crop of winter wheat, spring wheat, winter barley, spring barley or rye.

9. A method according to any one of claims 1 to 8 characterised in that the isoproturon and triallate are applied to the locus of weed infestation simultaneously.

10. A method according to claim 9 characterised in that the herbicides are applied simultaneously by means of a tank-mix prepared from emulsion concentrates of triallate with wettable powder or aqueous suspension concentrates of isoproturon.

11. A method according to claim 9 characterised in that the herbicides are applied simultaneously by means of liquid emulsion suspension concentrates or emulsifiable suspension concentrates containing both isoproturon and triallate.

Claims (1)

12. A method according to claim 9 characterised

in that the herbicides are applied simultaneously in granular formulations containing both isoproturon and triallate.

13. A method according to claim 10 character ised in that the tank-mix contains both isoproturon and triallate in the ratios of the former to the latter of 2.5:1 to 1:2.5 by weight respectively.

14. A method according to claim 10 characterised in that the tank-mix contains both isoproturon and trial late in the ratio of the former to the latter of 1:1 weight

15. A method according to claim 10, 13 or 14 characterised in that the tank-mix is applied to the locus of weed infestation at a rate such as to give 1.0 to 2.5 kg each of isoproturon and triallate per hectare.

16. A method according to claim 10, 13 or 14 characterised in that the tank-mix is applied to the locus of weed infestation at a rate such as to give 1.25 to 1.75 kg each of isoproturon and triallate per hectare.

17. A method according to claim 11 characterised in that the liquid emulsion suspension concentrates or emulsifiable suspension concentrates contain both isoproturon and triallate in the ratios of the former to the latter of 2.5:1 to 1:2.5 by weight respectively.

18. A method according to claim 11 characterised in that the liquid emulsion suspension concentrates or emulsifiable suspension concentrates contain both isoproturan and triallate in the ratios of the former to the latter of :1 by weight.

19. A method according to claim 11, 17 or 18 characterised in that the liquid emulsion suspension concentrate or emulsifiable suspension concentrate is applied, after dilution with water, to the locus of weed infestation at a rate such as to give 1.0 to 2.5 kg each of isoproturon and triallate per hectare.

20. A method according to claim 11, 17 or 18 characterised in that the liquid emulsion suspension concentrate or emulsifiable suspension concentrate is applied, after dilution with water, to the locus of weed infestation at a rate such as to give 1.25 to 1.75 kg each of isoproturon and triallate per hectare.

21. A method according to claim 12 characterised in that the granular formulation contains both isoproturon and triallate in the ratios of the former to the latter of 2.5:1 to 1:2.5 by weight respectively.

22. A method according to claim 12 characterised in that the granular formulation contains both isoproturon and triallate in the ratio of the former to the latter of 1:1 by weight.

23. A method according to claim 12,21 or 22 characterised in that the granular formulations are applied to the locus of weed infestation at a rate such as to give 1.0 to 2.5 kg each of isoproturon and triallate per hectare.

24. A method according to claim 12,21 or22 characterised in that the granular formulations are applied to the locus of weed infestation at a rate such as to give 1.25 to 1.75 kg each of isoproturon and triallate per hectare.

25. A method according to any one of the preceding claims characterised in that the combination of herbicides is applied to an area used, orto be used, for growing a crop of wheat or barley.

26. A method for the control of the growth of grass weeds and broad-leafed weeds according to claim 1 substantially as hereinbefore described.

27. A herbicidal composition for the control of the growth of grass weeds and broad-leafed weeds characterised in that the composition contains isoproturon and triallate in association with one or more compatible herbicidally acceptable diluents or carriers, wherein the ratio of isoproturon to triallate in the composition is 2.5:1 to 1:2.5 respectively by weight.

28. A herbicidal composition according to claim 27 characterised in that the ratio of isoproturon to triallate in the composition is 1:1 by weight.

29. A herbicidal composition according to claim 27 or 28 in the form of a liquid emulsion suspension concentrate.

30. A herbicidal composition according to claim 27 or28 in the form of a liquid emulsion suspension concentrate, characterised by a combined total of from 10% to 70% (wlv) of isoproturon and triallate, from 2 to 10% (w/v) of surface-active agent, from 0.1% to 5% (w/v) of thickener, from 15% to 87.9% by volume of organic solvent and from 0% to 60% by volume of water.

31. A herbicidal composition according to claim 27 or 28 in the form of a liquid emulsifiable suspension concentrate.

32. A herbicidal composition according to claim 27 or 28 in the form of a liquid emulsifiable suspension concentrate, characterised by a combined total of from 10% to 70% (w/v) of isoproturon and triallate, from 5% to 15% of surface-active agent, from 0.1% to 5% (w/v) of thickener and from 10% to 84.9% by volume of organic solvent.

33. A herbicidal composition according to claim 27 or 28 in the form of granular formulations.

34. A herbicidal composition according to claim 27 or 28 in the form of granular formulations, characterised by a combined total of from 2% to 20% by weight of isoproturon and triallate, from 0.1% to 10% by weight of surface-active agent, and from 70% to 97.9% by weight of granular carrier.

35. A herbicidal composition according to claim 33 or 34 characterised in that the granular formula- tion contains from 2% to 20% by weight of isoproturon, in the form of micronised particles, and triallate, and the granules have a diameter of from 150 to 1000 microns.

36. A herbicidal composition according to claim 35 characterised in that the isoproturon, in the form of micronised particles, and triallate are incorporated into the body of the granule, or the triallate is incorporated into the granule core and the micron- ised particles of isoproturon adhere to the surface of the granule.

37. A herbicidal composition according to any one of claims 33 to 36 characterised in that the granular formulation is of the compound type, as hereinbefore defined, wherein the micronised isop roturon particles are from 1 micron to 40 microns in diameter.

38. A herbicidal composition according to any one of claims 33 to 36 characterised in that the granular formulation is of the core type, as hereinbefore defined, wherein the micronised isoproturon particles are predominantly less than 10 microns in diameter.

39. A herbicidal composition according to any one of claims 33 to 38 characterised in that the granular carrier is a clay.

40. A herbicidal composition according to any one of claims 35to 39 characterised in that the granular formulation contains from 0.1% to 10% by weight of surface-active agent.

41. A method for the preparation of a granular herbicidal composition as claimed in any of claims 35 to 40 characterised by (i) intimately mixing the micronised isoproturon and triallate and, if desired, surface-active agent, with the inert solid carrier in powder form, if necessary in the presence of a suitable liquid, and then granulating the powder blend thus obtained and, if necessary, drying the granules thus obtained, or (ii) intimately mixing the micronised isoproturon and, if desired, surface-active agent, with the inert solid carrier in powder form, if necessary in the presence of a suitable liquid, granulating the powder blend thus obtained and, if necessary, drying the granules thus obtained, and then treating the isoproturon - containing granules with a solution of triallate in a suitable liquid to absorb the triallate into the granules and, if necessary, drying the granules thus obtained.

42. A method for the preparation of a granular herbicidal composition as claimed in any of claims 35 to 40 characterised by suspending the micronised isoproturon in a solution oftriallate and, if desired, surface-active agent, in a suitable liquid and applying uniformly the suspension thus obtained to granule cores of inert solid carrier, in a blender, whereby the triallate and, if present, surface-active agent, are absorbed into the granule core and the micronised isoproturon particles adhere to the surface of the granule core and, if necessary, drying the granules thus obtained.

43. A method according to claim 41 or 42 characterised in that the said inert solid carrier is a clay.

44. A method according to claim 41, 42 or43 characterised in that the liquid used in the preparation of the granular composition is one in which triallate has a solubility of at least 30% (weight/volume) and in which isoproturon has a solubility not greater than 5% (weight/volume).

45. A method according to claim 41,42,43 or 44 characterised in that the liquid used in the preparation of the granular composition is an aliphatic or aromatic hydrocarbon, a ketone, an alcohol, an ether, dimethylsulphoxide or a chlorinated hydrocarbon.

46. A method forthe preparation of granular herbicidal formulations comprising isoproturon and triallate as claimed in any one of claims 41 to 45 substantially as hereinbefore described with especial reference to any one of Example 2 to 7.

47. A herbicidal composition according to claim 27 substantially as herein before described in any one of Examples 1 to 13.