WO2004049806A1

WO2004049806A1 - Method of controlling unwanted vegetation

Info

Publication number: WO2004049806A1
Application number: PCT/GB2003/005255
Authority: WO
Inventors: Derek William Cornes; Judy Garrett
Original assignee: Syngenta Participations Ag
Priority date: 2002-12-04
Filing date: 2003-12-03
Publication date: 2004-06-17
Also published as: AU2003285579A1; GB0228326D0; AR042290A1

Abstract

A novel method of controlling unwanted glyphosate-tolerant vegetation is disclosed, the method comprising administering a synergistic herbicidally effective amount of a combination comprising mesotrione and glyphosate to the locus of the vegetation.

Description

Method of Controlling Unwanted Vegetation

The present invention relates to a method of controlling the growth of undesired glyphosate-tolerant vegetation by a combination comprising mesotrione and glyphosate. The protection of crops from weeds and other vegetation that inhibits crop growth is a constantly recurring problem in agriculture. To help combat this problem, researchers in the field of synthetic chemistry have produced an extensive variety of chemicals and chemical formulations effective in the control of such unwanted growth. Chemical herbicides of many types have been disclosed in the literature and a large number are in commercial use. Commercial herbicides and some that are still in development are described in The Pesticide Manual 12 Edition, published in 2000 by the British Crop Protection Council.

Glyphosate is a known herbicide, effective across a wide range of weeds. However, an increasing problem encountered in agriculture is the appearance of weeds that have developed a tolerance to glyphosate, and are therefore undamaged by or survive its application. By 'tolerance' is meant that these weeds are less easily damaged or killed by the application of glyphosate than the normal phenotype. Typically, these weeds show little or no damage or at least survive when glyphosate is applied at normal application rates. The tolerance arises naturally and occurs because of the selection pressure exerted on the weed population by repeated application of glyphosate. Some weeds have developed almost complete tolerance to glyphosate, that is, they are virtually undamaged by glyphosate at normal application rates. Sometimes, the word 'resistant' is also used to describe such weeds, in particular where they have the inherited ability to survive treatment by glyphosate. In this specification, the word 'tolerant' is intended to include 'resistant' and vice versa.

Glyphosate tolerance is obviously a problem, because either the weeds thrive to an increasing degree, which can drive down crop yields, or alternatively increased quantities of glyphosate must be used, which increases cost and risks environmental damage.

We have now discovered that a mixture of mesotrione and glyphosate can be used to control glyphosate-tolerant weeds. Mesotrione, 2-(2-nitro-4-methylsulphonyl benzoyl)-cyclohexanedione, is commercially available and is a selective herbicide with the formula

Surprisingly, it was found that a synergistic effect was obtained when mesotrione and glyphosate were administered in combination.

In some cases, herbicidally active ingredients have been shown to be more effective in combination than when applied individually, and this is referred to as "synergism". As defined in the Herbicide Handbook of the Weed Science Society of America, Seventh Edition, 1994, page 318, 'synergism [is] an interaction of two or more factors such that the effect when combined is greater that the predicted effect based on the response to each factor applied separately.' The present invention is based on the unexpected discovery that mesotrione and glyphosate, when applied as a combination, display a synergistic effect. This is totally unexpected, as one would not expect the combination to have any effect, over and above the effect of the mesotrione, when applied over glyphosate-tolerant weeds, since by definition, glyphosate has little or no effect on these weeds at normal application rates. Contrary to this expectation, we have surprisingly found that the presence of mesotrione appears to restore the tolerant weeds' susceptibility to glyphosate as the normal non-tolerant weeds.

Accordingly, the present invention provides a method of controlling unwanted glyphosate-tolerant vegetation, the method comprising administering a synergistic herbicidally effective amount of a combination comprising mesotrione and glyphosate to the locus of the vegetation. The term 'locus' is intended to include soil, seeds, and seedlings, as well as established vegetation. The herbicidal combination is suitably administered post-emergent i.e. after the weeds have emerged.

By 'mesotrione' we also include all agrochemically acceptable salts thereof, for example the metal salt, and also all tautomers thereof. By 'glyphosate' we also include all agrochemically acceptable salts thereof, for example the ammonium, isopropylammonium, sodium, potassium or trirnesium salt.

The synergistic combination of the present invention can provide one or more of a number of advantages over the use of the individual components. The rates of application of the individual components can be markedly reduced while maintaining a high level of herbicidal efficacy. The composition can have a considerably broader weed spectrum against which it is effective, than either of the components alone. The composition can have the potential to control weed species at a low application rate at which the individual components alone were ineffective. The composition can have a speed of action much faster than that which would have been predicted from the speed of the individual components.

By "herbicidally effective amount" is meant the quantity of such a compound or combination of such compounds that is capable of producing a controlling or modifying effect on the growth of plants. Controlling or modifying effects include all deviation from natural development, for example: killing, retardation, leaf burn, albinism, dwarfing and the like. The term plants refers to all physical parts of a plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, foliage, and fruits.

Suitably, the total amount of herbicide administered (i.e. mesotrione plus glyphosate) is from 100 to 2000 g a.i. per hectare, such as from 125 g a.i.per hectare and preferably from 450 to 1450 g a.i. per hectare. The ratio of mesotrione:glyphosate administered is suitably from 1 :75 to 2: 1 , and preferably from 1 :24 to 1 : 1.6.

The mesotrione and glyphosate may be administered together, for example as a tank mix or a pre-formulated mixed composition, simultaneously but as two separate formulations, or sequentially. If administered sequentially, either of the two components may be given first and the other is given after, either immediately or following an appropriate delay.

The process can be used in areas where there are no desired plants, such as crops, or in any area where there are no desired crops yet, but desired plants, such as crops, will be planted after application of the herbicidal combination ('pre-plant'), or where desired plants, such as crops, have been planted, but have not yet emerged ('pre-ernergence'). The process can also be used over a wide range of growing desired plants, such as crops ('post-emergence'). Examples of crops include, but are not limited to, corn (maize), wheat, rice, potato or sugarbeet. Suitable desired plants includes those which are tolerant to one or more of mesotrione and glyphosate (particularly when the process is used post- emergence), or tolerant to any other herbicide that may additionally be used in the combination. The tolerance can be natural tolerance which is inherent or which is produced by selective breeding or can be artificially introduced by genetic modification of the desired plants. Tolerance means a low susceptibility to damage caused by a particular herbicide. Plants can be modified or bred so as to be tolerant, for example to HPPD inhibitors like mesotrione, or EPSPS inhibitors like glyphosate. Cora (maize) is inherently tolerant to mesotrione and so the process is particularly useful for controlling glyphosate-tolerant weeds in glyphosate-tolerant corn.

Examples of weeds with tolerant phenotypes include Conyza Canadensis, Lolium rigidum, Lolium multifiorum and Eleusine indica. The components of the combination according to the present invention (whether administered together or sequentially) are suitably applied as an agriculturally acceptable composition. For example, the formulations can take the physical form of a dustable powder, gel, a wettable powder, a water dispersible granule, a water-dispersable or water-foaming tablet, a briquette, an emulsifiable concentrate, a microemulsifiable concentrate, an oil-in-water emulsion, a water-in-oil emulsion, a dispersion in water, a dispersion in oil, a suspoemulsion, a soluble liquid (with either water or an organic solvent as the carrier), an impregnated polymer film, or other forms known in the art. These formulations may be suitable for direct application or may be suitable for dilution prior to application, said dilution being made either with water, liquid fertilizer, micronutrients, biological organisms, oil or solvent. The compositions are prepared by admixing the active ingredient with adjuvants including diluents, extenders, carriers, and conditioning agents to provide compositions in the form of finely-divided particulate solids, granules, pellets, solutions, dispersions or emulsions. Thus, it is believed that the active ingredient could be used with an adjuvant such as a finely-divided solid, a mineral oil, a liquid of organic origin, water, various surface active agents or any suitable combination of these.

The active may also be contained in very fine microcapsules in polymeric substances. Microcapsules typically contain the active material enclosed in an inert porous shell which allows escape of the enclosed material to the surrounds at controlled rates. Encapsulated droplets are typically about 0.1 to 500 microns in diameter. The enclosed material typically constitutes about 25 to 95% of the weight of the capsule. The active ingredient may be present as a monolithic solid, as finely dispersed solid particles in either a solid or a liquid, or it may be present as a solution in a suitable solvent. Shell membrane materials include natural and synthetic rubbers, cellulosic materials, styrene- butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, polyureas, polyurethanes, other polymers familiar to one skilled in the art, chemically- modified polymers and starch xanthates. Alternatively, very fine microcapsules may be formed wherein the active ingredient is dispersed as finely divided particles within a matrix of solid material, but no shell wall surrounds the microcapsule. Suitable agricultural adjuvants and carriers that are useful in preparing the compositions of the invention are well known to those skilled in the art. Liquid carriers that can be employed include water, toluene, xylene, petroleum naphtha, crop oil, acetone, methyl ethyl ketone, cyclohexanone, acetic anhydride, acetonitrile, acetophenone, amyl acetate, 2-butanone, chlorobenzene, cyclohexane, cyclohexanol, alkyl acetates, diacetonalcohol, 1,2-dichloropropane, diethanolamine, p-diethylbenzene, diethylene glycol, diethylene glycol abietate, diethylene glycol butyl ether, diethylene glycol ethyl ether, diethylene glycol methyl ether, N,N-dimethyl formamide, dimethyl sulfoxide, 1,4-dioxane, dipropylene glycol, dipropylene glycol methyl ether, dipropyleneglycol dibenzoate, diproxitol, alkyl pyrrolidinone, ethyl acetate, 2-ethyl hexanol, ethylene carbonate, 1,1,1-trichloroethane, 2-heptanone, alpha pinene, d- limonene, ethylene glycol, ethylene glycol butyl ether, ethylene glycol methyl ether, gamma-butyrolactone, glycerol, glycerol diacetate, glycerol monoacetate, glycerol triacetate, glycerol triacetate, hexadecane, hexylene glycol, isoamyl acetate, isobornyl acetate, isooctane, isophorone, isopropyl benzene, isopropyl myristate, lactic acid, laurylamine, mesityl oxide, methoxy-propanol, methyl isoamyl ketone, methyl isobutyl ketone, methyl laurate, methyl octanoate, methyl oleate, methylene chloride, m-xylene, n-hexane, n-octylamine, octadecanoic acid, octyl amine acetate, oleic acid, oleylamine, o-xylene, phenol, polyethylene glycol (PEG400), propionic acid, propylene glycol, propylene glycol monomethyl ether, propylene glycol mono-methyl ether, p-xylene, toluene, triethyl phosphate, triethylene glycol, xylene sulfonic acid, paraffin, mineral oil, trichloroethylene, perchloroethylene, ethyl acetate, amyl acetate, butyl acetate, propylene glycol monomethyl ether and diethylene glycol monomethyl ether, methanol, ethanol, isopropanol, and higher molecular weight alcoholds such as amyl alcohol, tefrahy<kofurfuryl alcohol, hexanol, octanol, etc., ethylene glycol, propylene glycol, glycerine, N-methyl-2-pyrrolidinone, and the like. Water is generally the carrier of choice for the dilution of concentrates.

Suitable solid carriers include talc, titanium dioxide, pyrophyllite clay, silica, attapulgite clay, kieselguhr, chalk, diatomaceous earth, lime, calcium carbonate, bentonite clay, Fuller's earth, cotton seed hulls, wheat flour, soybean flour, pumice, wood flour, walnut shell flour, lignin, and the like such as described in the CFR 180.1001. (c) & (d).

A broad range of surface-active agents are advantageously employed in both solid and liquid compositions, especially those designed to be diluted with carrier before application. The surface-active agents can be anionic, cationic, nonionic or polymeric in character and can be employed as emulsifying agents, wetting agents, suspending agents, or for other purposes. Typical surface active agents include salts of alkyl sulphates, such as diethanolammonium lauryl sulphate; alkylarylsulphonate salts, such as calcium dodecylbenzenesulphonate; alkylphenol-alkylene oxide addition products, such as nonylphenol-C.sub.18 ethoxylate; alcohol-alkylene oxide addition products, such as tridecyl alcohol-C.sub.16 ethoxylate; soaps, such as sodium stearate; alkylnaphthalenesulphonate salts, such as sodium dibutylnaphthalenesulphonate; dialkyl esters of sulfosuccinate salts, such as sodium di(2-ethylhexyl) sulfosuccinate; sorbitol esters, such as sorbitol oleate; quaternary amines, such as lauryl trimethylammonium chloride; polyethylene glycol esters of fatty acids, such as polyethylene glycol stearate; block copolymers of ethylene oxide and propylene oxide; and salts of mono and dialkyl phosphate esters.

Other adjuvants commonly utilized in agricultural compositions include crystallization inhibitors, viscosity modifiers, suspending agents, spray droplet modifiers, pigments, antioxidants, foaming agents, light-blocking agents, compatibilizing agents, antifoam agents, sequestering agents, neutralizing agents and buffers, corrosion inhibitors, dyes, odorants, spreading agents, penetration aids, micronutrients, emolients, lubricants, sticking agents, dispersing agents, thickening agents, freezing point depressants, antimicrobial agents, and the like.

If necessary or desired for a particular application or crop, the composition(s) making up the combination of the invention may contain an antidotally effective amount of an antidote (sometimes also called a 'safener') for mesotrione and/or glyphosate. Those skilled in the art will be familiar with suitable antidotes. Further, other biodically active ingredients or compositions may be combined with the synergistic combination of the invention. For example, the combination may contain, in addition to mesotrione and glyphosate, insecticides, fungicides, bactericides, acaracides or nematocides, in order to broaden the spectrum of activity.

The invention will now be further described by way of example only. 48 pots each of 3 different biotypes of Conyza Canadensis (Marestail/Horseweed) were propagated in the greenhouse under warm climate conditions until they reached a mean rosette diameter of 10cm. The 3 biotypes used were: 'Susceptible' - Wyandot County, Ohio 'Intermediate' - Putnam Country, Ohio 'Resistant' - Brown County, Ohio.

3 replicates were used.

Treatment was applied over a two-day period.

Touchdown IQ applications (125, 250 and 500g ai/ha - alone and for the first component of each sequence) were made the first day, and Callisto applications (12.5, 25, 50g ai/ha - alone and for the second component in each sequence) were made on the second day.

Applications were made in deionised water at 150 1/ha (~15GPA) using a standard Teejet 8002E flat fan nozzle in a tracksprayer. Conditions were ambient (warm and humid) at application and 1 hour drying time was allowed after each application.

Results were taken at various days after application (i.e. days after the second application in a sequence). Pots were sub-irrigated from this point onwards.

Claims

1. A method of controlling unwanted glyphosate-tolerant vegetation, the method comprising administering a synergistic herbicidally effective amount of a combination comprising mesotrione and glyphosate to the locus of the vegetation.

2. The method of claim 1, wherein the total amount of mesotrione and glyphosate administered is from 100 to 2000 g a.i. per hectare.

3. The method according to any one of claims 1 to 2, wherein the ratio of mesotrione to glyphosate administered is from 1:75 to 2:1.

4. The method according to any one of claims 1 to 3, wherein the mesotrione and glyphosate are administered simultaneously.

5. The method according to claim 4, wherein the mesotrione and glyphosate are administered as a tank mix.

6. The method according to claim 4, wherein the mesotrione and glyphosate are administered as a single composition comprising mesotrione and glyphosate.

7. The method according to claim 4, wherein the mesotrione and glyphosate are administered as two separate formulations.

8. The method according to any one of claims 1 to 3, wherein the mesotrione and glyphosate are administered sequentially.

9. The method according to claim 8, wherein the mesotrione is administered first.

10. The method according to claim 8, wherein the glyphosate is administered first.

11. The method according to any preceding claim, wherein the glyphosate-tolerant vegetation is in a useful crop.

12. The method according to claim 11, wherein the useful crop is maize.

13. The method according to any one of claim 11 or 12, wherein the useful crop is tolerant to one or both of mesotrione and glyphosate.

14. The method according to any one of claims 11 to 13, wherein the combination is administered pre-emergence.

15. The method according to any one of claims 11 to 13, wherein the combination is administered post-emergence.

16. The method according to any preceding claim, wherein the combination further comprises an antidote.

17. The method according to any preceding claim, wherein the combination further comprises one or more additional biocidally active ingredients.