FR2589327A1 - HERBICIDAL BLENDS OF PYRIDINOXYALCANOIC ACID DERIVATIVES AND PHENOXYBENZOIC ACID DERIVATIVES AND THEIR USE FOR THE TREATMENT OF CULTURES - Google Patents

Abstract

HERBICIDE MIXTURE OF PYRIDINOXYALCANOIC ACID DERIVATIVES AND PHENOXYBENZOIC ACID DERIVATIVES. THEIR APPLICATION TO CEREAL WEED CONTROL.

Description

The present invention relates to novel herbicide mixtures as well as

their use for treatment

  crops, including cereals.

  Various pyridine herbicides (and more specifically derivatives of pyridinoxyalkanoic acids) and in particular fluroxypyr and its derivatives of formula: NR1R2

X1T _ X1

X2) N 0 - CH - CO - O - R4 ()

I R in which:

-1 2

  - R and R are the hydrogen atom or a lower alkyl radical (that is to say C14), - 1 is a halogen atom, preferably chlorine, - X2 is a halogen atom, preferably fluorine, - R3 is a hydrogen atom or a methyl radical, - R4 is a hydrogen atom or an agriculturally acceptable metal or ammonium cation, or an alkyl radical

  preferably having 1 to 12 carbon atoms.

  More specifically, fluroxypyr-ester is known which is a compound of formula (I) in which R 1, R 2 and R 3 are hydrogen, X 1 is Cl, 2 is F and R 4 is a methyl-1 heptyl radical. It is therefore the product of formula (III)

NH2

C "ci

F <3-CO - CH - (CH 2) 5 - CH 3 (III)

  This compound has sometimes also been described in its acid, salt and other ester forms, and has also been named

under the name Dowco 433.

  The pyridine herbicides of formula (I) are of interest, in particular by their activity on certain dicotyledonous weeds in relatively low doses, and at relatively advanced stages of development of these weeds. However, the spectrum of activity of these compounds is not extremely broad and, for their practical use, it is good to

  find ways to expand this spectrum.

  Thus, some combinations of these products have already been proposed with various herbicides such as isoproturon (European patent 67713), bromoxynyl (European patent 67712) or benazoline (European patent 101168). Some synergy of the components of these

  binary mixtures could be demonstrated.

  The use of Dowco 433 with diphenyl ether herbicides, especially diclofop-methyl (Weed Research 24 185-190, 1983), has been further suggested, although this reference states that the products so associated are fully compatible the results presented are, however, mediocre and unsatisfactory. With regard to grasses, the addition of Dowco 433 only slightly modifies the activity of diclofop methyl, and sometimes by decreasing this activity; with respect to broadleaf weeds, especially cleavers, there is a clear antagonism between Dowco 433 and diclofop-methyl, the herbicidal activity of Oowco 433 being much better

than that of the mixture.

  Given such a state of the art, it was obviously discouraged to try to associate fluoroxypyr (or

  Dowco 433) with other diphenyl ether herbicides.

  It has now been found, and this is the subject of the present invention, that surprisingly excellent herbicidal activity was obtained by combining the products of formula (1), and preferably of formula (III) with phenoxybenzoic acid derivatives of the formula:

5

  Cl.CO -R x3 N2 (I) wherein: - X3 is C1 or CF3,

3

  - R is - 0 - CH3 or - ONa or - O - CH - COOR8 or I

- NH - S02 - R6, R7

  - Z is - N = or - CH =, preferably - CH =, - R and R having the same meanings as those given respectively for R3 and R4 about the formula (I), and R6 representing a lower alkyl radical, preferably the methyl radical; in this formula (II), R4 is preferably the ethyl radical. Preferably, the oifenox is used for which

  X3 is the chlorine atom, Z is - CH =, R5 is O -

  CH3. It may be noted that the formula of bifenox is particularly close to that of diclofop-methyl so that the combination of the products of formula (I) with the

  bifenox seemed particularly to be avoided.

  The invention therefore relates to herbicidal compositions, intended in particular for use in postemergence against weeds, and more particularly against dicotyledonous weeds, and characterized in that they comprise at least one compound of formula (I), preferably the fluroxypyr-ester or Dowco 433 of formula (III), and at least one compound of

  formula (11), preferably bifenox.

  To obtain favorable results, these compounds of formulas (I) and (II) are generally used in respective weight proportions (I) / (II) between

  0.02 and 2, preferably between 0.08 and 0.5.

  The invention also relates to a method for controlling weeds in crops, especially cereals (especially wheat, barley, rye and oats), which consists of applying postemergence (or postemergence, according to a term synonym) of the crop and / or weeds, an effective amount of the compositions according to the invention. The doses of use of the compounds of formulas (I) and (II) used in the invention may vary within wide limits, in particular according to the nature of the weeds to be eliminated and the degree of infestation.

  usual crops for these weeds.

  The post-emergence application therefore consists in applying the compositions based on active ingredients of formula (I) and (II) on the vegetation and in particular on the weeds to be eliminated when they present a

green foliage.

  Generally, the compositions according to the invention are applied in quantities such that the compound of formula (I) or (III) is applied at a dose of between 0.05 and 1 kg / ha, preferably between 0.1 and 0, 4 kg / ha, whereas the compound of formula (II) is applied at a dose generally of between 0.2 and 5 kg / ha, of

preferably between 0.5 and 1 kg / ha.

  For their practical use, the active ingredients of

  mixtures according to the invention are rarely used alone.

  Most often these compounds are part of more elaborate compositions. These compositions, which can be used as herbicidal agents, contain, as active ingredients, each of the compounds of formulas (I) and (II) in association with solid or liquid carriers, acceptable in agriculture and / or surfactants which are also agriculturally acceptable. . In particular, the usual inert carriers and surfactants are usable. These more complex compositions are also part of the invention. These compositions according to the invention may also contain all kinds of other ingredients such as, for example, protective colloids, adhesives, thickeners, thixotropic agents,

  penetration, stabilizers, sequestering agents, etc.

  as well as other known active ingredients with pesticidal properties (in particular insecticides, fungicides or herbicides) or with properties regulating the growth of plants. More generally, the compounds used in the invention may be combined with any solid or liquid additives corresponding to the techniques

  the usual formulation.

  As herbicidal active ingredients which may be associated with the compositions according to the invention, there may be mentioned especially isoproturon and ioxynyl which are generally in amounts such that 0.1 to 5 kg / ha are applied, preferably 0.2 to 4 kg / ha, the proportion third / (I) + (II) (that is to say, the weight ratio of the third active ingredient herbicide on all the active ingredients of formulas (I) and (II) ^ being generally

  between 0 and 3, preferably 0.1 and 2.

  As other active materials that may be associated with the compositions according to the invention, mention may also be made of chlortoluron, metabenzthiazuron, metoxuron, imazamethabenz, flamprop isopropyl,

  benzoylprop-ethyl, flufenprop-methyl.

  In general, the compositions according to the invention usually contain from about 0.05 to 95% (by weight) of one or more active ingredients of formulas (I) and (II), from about 1% to about 95%. one or more solid or liquid carriers and possibly

  From about 0.1 to about 50% of one or more surfactants.

  By the term "carrier", in the present description, means an organic or inorganic material, natural or synthetic, with which the active ingredients are associated to facilitate their application on the plant, on seeds or on the ground. This support is therefore generally inert and must be acceptable in agriculture, especially on the treated plant. The support may be solid (clays, natural or synthetic silicates, silica, resins, waxes, solid fertilizers, etc.) or liquid (water, alcohols, in particular butanol, esters, especially methylglycol acetate, and ketones , especially cyclohexanone and isophorone, petroleum fractions, aromatic hydrocarbons, in particular xylenes, or paraffinics, chlorinated aliphatic hydrocarbons, especially trichloroethane, or aromatic hydrocarbons, in particular chlorobenzenes, water-soluble solvents such as dimethylformamide, dimethylsulfoxide,

  N-methylpyrrolidone; liquefied gases, etc.).

  The surfactant may be an emulsifier, dispersant or wetting agent of ionic or nonionic type or a mixture of such surfactants. There may be mentioned, for example, salts of polyacrylic acids, salts of lignosulfonic acids, salts of phenolsulphonic or naphthalenesulphonic acids, polycondensates of ethylene oxide with fatty alcohols or with fatty acids or with fatty amines. substituted phenols (especially alkylphenols or arylphenols), salts of sulfosuccinic acid esters, taurine derivatives (especially alkyltaurates), phosphoric esters of polyoxyethylated alcohols or phenols, acid esters fatty acids and polyols, functional derivatives

  sulphates, sulphonates and phosphates of the foregoing compounds.

  The presence of at least one surfactant is

usually essential.

258,932?

  The compositions according to the invention may be in various forms, solid or

  liquids, but liquid compositions are preferred.

  As forms of solid compositions, mention may be made of wettable powders and dusting powders (containing active compounds, that is to say compounds of formulas (I) and (II) of up to 80%) and the granules, in particular those obtained by extrusion, by compacting, by impregnation of a granulated support, by granulation from a powder (the content of compound of formula (I) in these granules being between 0.5 and 80 A for

these latter cases).

  As forms of liquid or intended compositions

  to constitute liquid compositions during -

  the application may be made of solutions, in particular emulsifiable concentrates, emulsions and

concentrated suspensions.

  The emulsifiable or soluble concentrates also most often comprise 5 to 80% of active ingredients, the emulsions or solutions ready for application.

  containing, for their part, 0.001 to 20% of active ingredients.

  In addition to the solvent, the emulsifiable concentrates may contain, when necessary, 2 to 50% of suitable additives, such as stabilizers, surfactants, penetration agents,

  corrosion, dyes, adhesives.

  From these concentrates, it is possible to obtain, by dilution with water, emulsions of any desired concentration, which are particularly suitable for application

on plants.

  As an example, here is the composition of some

emulsifiable concentrates: -

Example 1

  - active ingredients 100 g - polyethoxylated alkyl phenol 100 g - ethylene glycol methyl ether 400 g - aromatic petroleum fraction distilling between 160-185 C 400 g

Example 2

  According to another emulsionnaole concentrate formulation, use is made of: active substances 50 g epoxidized vegetable oil 25 g mixture of alkylaryl sulfonate and polyglycol ether and fatty alcohols 100 g dimethylformamide 250 g -xylene 575 g Concentrated suspensions, which are applicable in spraying, are prepared so as to obtain a stable fluid product which does not settle (fine grinding) and they usually contain from 10 to 75% of active ingredients, from 0.5 to 30% of agents. surfactants, from 0.1 to 10% of thixotropic agents, from 0 to 30% of suitable additives, such as antifoams, corrosion inhibitors, stabilizers, penetrants and adhesives and, as a carrier, water or an organic liquid in which the active ingredient is sparingly soluble or non-soluble: some organic solids or mineral salts may be dissolved in the carrier to help prevent

  sedimentation or as antifreeze for water.

  By way of example, here is a composition of the above-mentioned suspension:

Example 3

  active ingredients 500 g polyethoxylated tristyrylphenol phosphate 50 g polyethoxylated alkylphenol 50 g sodium polycarboxylate 20 g ethylene glycol 50 g organopolysiloxane oil antifoam polysaccharide 1.5 g water 316.5 g aqueous dispersions or emulsions , Ootenues diluent with water a suspension or concentrated dispersion according to the invention are included in the general scope of the compositions used in the present invention. The emulsions can be of the water-in-oil or oil-in-water type and they can have

  a thick consistency like that of a "mayonnaise".

  All these dispersions or aqueous or boiled emulsions are applicable to crops to be weeded by any suitable means, mainly by spraying, at doses which are generally of the order of 100 to 1200

liters of slurry per hectare.

  The following examples, given in a non-limiting way, illustrate particular compositions of active ingredients of formulas (I) and (II), as well as their

herbicidal use.

  Examples 4 to 11: A first slurry (Examples 4, 6, 8, 10) was prepared for application by adding, to 10 liters of water,: on the one hand 15 ml of an emulsifiable concentrate containing g / l of ester of formula (III) (Dowco 433), and, on the other hand, 31.25 ml of concentrated aqueous suspension

containing 480 g / 1 of oifenox.

  This mixture, applied to plots of 30 m2, corresponds to the application of 500 1 / ha of slurry containing a mixture of Dowco 433 and bifenox, these active ingredients being themselves applied at the rate of

  g / na for Dowco 433 and 750 g / ha bifenox.

  In parallel, a second slurry (Examples 5, 7, 9, 11) of double concentration of the previous one and corresponding to the application of Dowco 433 and bifenox in respective amounts of 300 g / ha and 1500 g / ha was produced in parallel. These slurries were applied postemergence to cereal crops and herbicide effects on crop and weeds were observed compared to untreated control plots. A

  100% efficiency corresponds to a 100% destruction.

  An efficiency of 0% corresponds to a state of vegetation on the treated plot identical to that on the untreated plot; if it is about culture, an efficiency of

  0% corresponds to total selectivity.

  The results were also observed on neighboring plots treated with a corresponding dose of

  bifenox alone (examples bis, 4bis to 11bis).

  The following results were obtained.

Example I 4 I 4Dis I 5 I 5bis I

II 'I.II I

  I Cultivation and stage of III development of winter wheat winter wheat II crop at first start of breeding season start of application of herbicide III Primary weeds and stage III Galium - I Galium - II development during application of 3 - 5 stems I 3 - 5 stems II Herbicide application IIII _ _ _ I, I i I IDowco Herbicide and dose 4331 Bifenox IDowco433I I of application I 150g / hal I 300g / hal Bifenox I I + Bifenoxl 750g / ha I + Bifenoxl 1500g / hal 1,750g / ha I 11500g / hal 1 I Efficacy 3 weeks III after treatment III ICulture IIIII (phytotoxicity) i 15 I 2 I 23 I 0 I

I I I 1

  Average of weed problems I 90 I 43 I 95 I 60 I g II I I I Ialuminium aparine I 90 I 50 I 95 I 60 I I_; Efficiency 6 weeks after treatment I (I) phytotoxicity I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

I I I I

12 2589327

  Example I 6 1 6bis I 7 I 7bis I II II II Crop and stage of winter wheat development - I winter wheat - II crop during recovery recovery II application of herbicide main herbs and stage of Veronica Veronica II development of celiac (8 to 12 cm) (8 to 12 cm) I at I Stellaria I Stellaria I herbicide application I (10 at 15 cm) I (10 to 15 cm) I HerDicide and dose IDowco-4331 Bifenox IDowco4331 Bifenox II application 1150g / ha +1 750g / ha 1300g / ha I 1500g / hal I f13ifenox 1 I + Bifenox I 1750 g / ha 1500g / haI I f II, f I Efficacy 3 weeks II after treatment II Crop II (phytotoxicity) 4 I 2 1 10 f OIIIIII ii Average of bad weeds 60 30 I 70 I 60 1 i, III f1 I IStellaria media 60 0 I 60 I 25 I Veronica hederifolia I 97 f 92 1 99 1 97 I f f. I., I.,. EFFECTIVENESS 6 WEEKS II AFTER TREATMENT I Crop (phytotoxicity) 4 2 10 IOI fff II f Average weed I 60 30 I 70 1 60 II f II I1 Stellaria media 60 0 60 I 25! Veronica ned. 100 100! 100 I 100 I I 1 I 1 I I Example 8 I 8bis I 9 I 9bis I l. I II I Cultivation and stage of development of winter barley Winter barley crop at the end of tillering I end of tillering! herbicide application I

Primary weeds

  Cipals and stage of Aphanes (4-5 ADhanes (4 to 5 II development of cells) leaves) during ap- Stellaria (15 cm) I Stellaria (15 cm) I plication herbicide I Viola (6 to 8 I Viola (6 to 8 I) leaves) II Herbicide and dose IDowco 4331 Bifenox tDowco4331 Bifenox I application 1150g / ha +1 750 g / hal300g / ha + l 1500g / hal tI tBiEfénox Bifenox I It I 750g / ha I i1500q / hal Effectiveness 3 weeks after treatment I 1, 1 III t Crop II (phytotoxicity) 10 I 2 t 10 I 3 I l I t, I, 1 ,, t Average Pests and diseases 60 I 15 60 I 15 I II I I I IAphanes arvensis t 60 40 II ti II t IStellaria media 60 2 60 I 2

I I I..I

  Veronica hederifolia - Viola tricolor 70 60 70 68 I t I t I t I t I t It is effective 6 weeks after treatment I Crop I (Phytotoxicity) I 4 I 0 7 4 I. The average of the weed species is 60%. I 10bis 1 11 I libis I

I I II

  I Cultivation and stage of development of Winter I winter barley I cropping during application Imaging I mid-tilling Application of herbicide III Primary weeds and Galium stage aparineI Galium aparine II development of cel- I (3 to 8) 1 (3 to 8 rootlets) I I at I-1 Myosotis (7 cm) I Myosotis (7 cm) II application of herbicide I Veronica hed., I Veronica hed., II 1I early bloom I early bloom II Herbicide and dose IDowco 4331 Bifenox IDowco433I 3ifenox 1 I application 1150q / ha +1 750 g / hal300g / ha + l 1500g / hal I | JBifenoxI IBifenox { I, II 750g / ha I 11500g / hal 1 II I Efficacy 3 weeks IIIII after treatment IIIII i, IIII _I ICulture IIIII (phytotoxicity) I 30 1 3 1 30 I 4 l

I.V. I

  Average of bad weeds 1 95 85 98 I 85

I IIII

I II II

  I Galium aparine 1 93 1 70 1 97 I 70 1

I I I I I

I II II

  IMyosotis arvensis I 97 93 1 99 I 97 1

I II II

I Stellaria media I I

I I I. I I

  l I Veronica hed. 97 1 92 1 99 1 97 1

I_ _ _ _ _ _ _ _ _ _ _ 1. I 1

I I I I I I I

  Efficiency 6 weeks after treatment I I I I

1. 1 I 1. XI I

  ICulture I (phytotoxicity) I 10 0 1 10 I 2 I 1

I II II

  Average of weed diseases I 98 70 98 1 78

I IIII

  IGalium aparin I 99 60 99 I 85 I I I I L. I ... I IMyosotis arvensis 95 40 1 98 i 60 1 VrncI.IdI0 I0 I I I I I I I I I Veronica hed. Examples 12 to 15: A post-emergence herbicide treatment was carried out on plots of 30 m2 of soft wheat and winter barley (2 plots for wheat, 2 plots). for barley for each of the trials) which were at the beginning of tillering as to their stage of development. The main weeds that infested these plots were Alopecurus and Avena fatua for grasses, and Galium aparine, Veronica ned. and Viola tricolor for broadleaf weeds. These herbicide treatments have employed ternary mixtures which are especially suitable for the treatment of both grass and dicotyledonous weeds. More precisely, the plots were treated with 500 l / na of slurry obtained by mixing water with a certain amount of: concentrated aqueous suspension of bifenox at 480 g / l, concentrated aqueous suspension of isoproturon at 500 g / l, Dowco 433 concentrate in the form of product of formula (III), this concentrate being either in the form of an aqueous suspension at 250 g / l or in the form of an emulsifiable concentrate at 200 g / l. However, the results obtained with these two types of formulation are practically identical, so that the results detailed hereinafter are given only for treatments starting from

emulsionnaole concentrate.

  The exact amount of cnacun of these concentrates was determined in order to obtain the dose of materials

indicated below.

  The weed efficiency and phytotoxicity to crops were measured as previously, expressed as a percentage on a scale of 0 to 100%. This efficacy and phytotoxicity were measured. days after the herbicide treatment. However, in the case of grasses, in order to have significant results, the effectiveness at the time of heading (formation of cereal ears) was specifically determined. The results obtained are as follows: Example I 12 13 14 15 Dose of Dowco 433 125 150 150 300 I in g / ha Dose of Bifenox 1 750 1 750 1 600 1 1500 I in g / ha 1 1 1 I Dose of isoproturonl 1400 1400 1400 2800 l_ g / ha II Weight ratio 0.167 0.2 1 0.25 1 0.2 I Dowco / bifenox I IPhytotoxicity 1 2 1 5 1 5 1 15 vs III i I Cultural 1 1 1 7 I Efficiency IIII average for weed III Overall value 85 90 1 90 1 97 IGraminea1Alopecurus I 90 1 90 1 95 1 95 I IAvena fatua 1 85 1 80 1 93 98 IDicotyl I Galium 1 87 1 95 I 92! 99 Idones IVeronica hedl 85 1 92 I 90 I 99 II Iviola III l Itricolor I 99 I 99 1 99 I 100 Examples 16 to 18: Treatments similar to those of Examples 12 to 15 were carried out, but on plots infested with weeds especially difficult to eliminate including Lolium multiflorum, which led to use

  much higher herbicide rates.

  The results obtained were as follows: Example 16 I 17 I 18

I I I

  I Dose of Dowco 433 163 I 195 I. 390-II in g / ha IIII Dose of Bifenox 1 975 I 975 i 1950 I in g / ha IIIII Dose of isoproturoni 1800 1 1800 1 3600 I in g / ha I Weight ratio 1 0,167 1 0,2 1 0,2 I Dowco / bifenox I 1 1 1 I Phytotoxici-I Wheat IOIO 0 4 ty vis-à-vis IIII of the culturalOrge I 2 1 3 1 3

I I I I. I

  Efficiency 1 92 95 1 99 I mean to weed II II Overall efficacy I IGraminéesl Avena I 50 80 I 92 II Lolium I 92 92 97 I Lyicotylé-lVeronica hed 100 1 100 1 100 1 I dones Examples 19 to 22: Herbicide treatments were carried out similar to those of Examples 12 to 15; however, in these trials, the treated cereal plots were mostly infested with dicotyledonous weeds and ternary herbicide mixtures based on Dowco 433 (product of formula (III)), bifenox and ioxynil were used; this was carried out as an aqueous solution of its sodium salt with a

  concentration of 400 g / l (counted as unsalified product).

  Ioxynil is 4-hydroxy 3,5-diiodo-cyanobenzene.

  The results obtained are presented below.

  Sow tests using Dowco 433 as a concentrated aqueous suspension instead of an emulsifiable concentrate resulted in very similar results.

are therefore not repeated below.

  Example I 19 20 21 22 I Dose of Dowco 433 125 150 150 300 I in q / ha I Dose of 3ifenox | 750 1,750 | 600 | 1500 I in q / ha 1 3 3 3 i Dose of ioxynyl 200 200 200 400 I in q / ha I Weight ratio 1 0.167 1 0.2 1 0, 25 1 0.2 I Dowco / bifenox 3 3 3 3 I Phytotoxici- 11 3 3 31 3 Ie I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I 3 3 3 3

I I

  I Average efficiency with regard to bad herbs Oicotyledonous I IGalium aparine 95 98 90 98 I Istellaria media I 90 90 90 98 I Hericifolial iveronica 90 I 95 I 90 I 98 g Veronica persici j 100 100 100 100 I Viola tricolor I 98 1 98 1 98 g 98 I Throughout the above description, the correspondence between Latin, English and French names of bad heroes is as follows: Latin name Avena fatua Lolium multiflorum Galium aparine I French name I English name II Folle oats I aild oat II Ryegrass I Rye grass II Cleavers I Cleaver I Stellaria media IStellaria or mourrul ChicKweed I Iveronica hederifolial Veronica at Ivyleaf speedwelil II Ivy leaf II Veronica persica IVeronic of Persia I3irdseye speedwell I Viola tricolor I Thought I Pansy II Alopecurus III myosuroid i Vulpin 1 1Blackgrass I I Aphanes arvensis I Alchemilla I Parsley-piert I Myosotis arvensis I Myosotis I Forget-me-not I The results presented in Examples 4 to 22 show whereas, contrary to what could be expected from the state of the art, the compositions according to the invention and the process which uses them lead to particularly excellent herbicidal results, devoid of antagonisms; these compositions also

a broad spectrum of activity.

Claims (10)

  1) A method for controlling weeds in crops, characterized in that postemergence is applied an effective amount of a composition comprising a pyridine derivative of formula: NR1R2 x X1 2 4   Wherein R1 and R2 are the hydrogen atom or a lower alkyl radical (i.e. C1_4), - xi is a halogen atom, preferably chlorine, - x2 is a halogen atom, preferably fluorine, - R3 is a hydrogen atom or a methyl radical, - R4 is a hydrogen atom or a metal cation or agriculturally acceptable ammonium, or an alkyl radical preferably having 1 to 12 carbon atoms, and a phenoxybenzoic acid derivative of formula: Cl, CO-R x3 / jc. NO2 (II) wherein: - 3 is Cl or CF3, - R is - O - CH3 or - ONa or - O - CH - COOR8 or I - NH - SO2 - R6 R7   - Z2est - N = or - CH =, preferably - CH = - Z is - N = or - CH =, preferably - CH = - R7 and R having the same meanings as those given respectively for R3 and R about formula (I) and R6 representing an alkyl radical   lower, preferably the methyl radical.   2) Process according to claim 1, characterized in that a cereal culture is treated, preferably the   ole or barley or rye or oats.   3) Method according to claim 2, characterized in that treated a weed infested crop comprising one or more of the bad heroes selected from the cleavers, the stellar, a veronica, thought.   4) Method according to one of claims 1 to 3,   characterized in that the derivative of formula (II) is bifenox and the derivative of formula (I) is a product of formula: ## STR2 ## having the same meaning as in the claim 1 and preferably being radical methyl-1 heptyl.   Method according to one of Claims 1 to 4,   characterized in that the compound of formula (I) is applied at a dose of between 0.05 and 1 kg / ha, preferably between 0.1 and 0.4 kg / ha and that the compound of formula (II) is applied at a dose of between 0.2   and 5 kg / ha, preferably between 0.5 and 1 kg / ha.   6) Method according to one of claims 1 to 5,   characterized in that the applied composition contains   in addition isoproturon and / or ioxynyl.   7) A herbicidal composition, characterized in that it comprises a pyridine derivative of formula: NR1R2 xi i X2 CH - CH - CO   where: R1 and R2 are hydrogen or a lower alkyl radical (i.e. C1 4), 1 is an atom halogen, preferably chlorine; X is a halogen atom, preferably fluors; R 3 is a hydrogen atom or a methyl radical; R 4 is a hydrogen atom or a metal or ammonium cation; agriculturally acceptable, or an alkyl radical preferably having 1 to 12 carbon atoms, and a phenoxybenzoic acid derivative of formula x / -ON2 (OI) in which: X3 is C1 or CF3, - R5 is -O - CH3 or - ONa or - 0 - CH - COOR8 or I - NH - SO2 - R5 R3   - Z is - N = or - CH =, preferably - CH = - R7 and R8 having the same meanings as those given respectively for R3 and R4 with respect to the formula (I) and R6 representing a lower alkyl radical, preferably the methyl radical 8) The composition according to claim 7, characterized in that the product of formula (I) has the formula: ## STR2 ## having the same meaning as in claim 7 and preferably being the methyl-1 heptyl radical,   and that the product of formula (II) is bifenox.   9) Composition according to one of claims 7 or 8,   characterized in that it further contains isoproturon and / or ioxynil.   Composition according to one of Claims 7 to 9,   characterized in that the compounds of formula (I) and (II) are in respective weight proportions (I) / (II) of between 0.02 and 2, preferably between 0.08 and 0.5.   11) Composition according to one of claims 7 to 10,   characterized in that it is in the form of aqueous suspensions.   12) Composition according to claim 11, characterized in that they comprise 10 to 75% by weight of materials   active agents of formula (I) and (II) associated with a support.   13) Composition according to claim 12, characterized   in that it comprises 0.5 to 30% of surfactant active.