WO2012007908A1

WO2012007908A1 - Weed control method

Info

Publication number: WO2012007908A1
Application number: PCT/IB2011/053114
Authority: WO
Inventors: Gordon Vail; Charles Foresman
Original assignee: Syngenta Participations AG
Current assignee: Syngenta Participations AG
Priority date: 2010-07-16
Filing date: 2011-07-12
Publication date: 2012-01-19
Anticipated expiration: 2013-01-16

Abstract

The present invention relates to a method of controlling a HPPD recalcitrant and triazine resistant weed at a locus, said method comprising applying to the locus a herbicidal composition comprising a HPPD inhibiting herbicide and a triazine herbicide.

Description

Weed Control Method

The protection of crops from weeds and other vegetation that inhibit 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, 15th edition, published in 2009 by the British Crop Protection Council.

Hydroxyphenylpyruvate dioxygenase (HPPD) inhibiting herbicides are a class of herbicides that can be used both pre- and/or post-emergence to provide effective control of a wide variety of weeds. It has recently been discovered, however, that certain weed biotypes do not seem to be adequately controlled by post-emergence applications of HPPD-inhibiting herbicides at application rates which would normally be expected to afford adequate control (by "normally" it is meant that the herbicide is applied at a typical commercial rate, as recommended by the herbicide manufacturer. Thus a normal post-emergence application rate for the HPPD-inhibiting herbicide mesotrione would be, for example, from 30 to 210 g/ha, more typically from 70 to 150 g/ha). For the purposes of the present invention, such weed biotypes are referred to as "HPPD recalcitrant weeds". Thus, a HPPD recalcitrant weed is less easily damaged or killed by a post-emergence application of the HPPD-inhibitor than the normal weed phenotype at normal application rates. Thus, "HPPD recalcitrant weeds" are weeds (in particular Palmer amaranth or common waterhemp) that have increased tolerance to HPPD inhibitors applied pre or post but are not resistant to HPPD inhibitors.

It has also been discovered that certain of these HPPD recalcitrant weeds also exhibit resistance to triazine herbicides. Triazine-resistant plants are known in the art and referred to, for example, in US 7,071,147 which teaches that triazine-resistant plants can be successfully controlled via the application of mesotrione and a triazine herbicide.

We have now discovered that HPPD recalcitrant and triazine-resistant weeds can also be successfully controlled via the application of a herbicidal composition comprising a HPPD-inhibiting herbicide and a triazine herbicide. This finding is surprising in that weed biotypes that are not adequately controlled by individual treatment with an HPPD-inhibiting herbicide or triazine herbicide would similarly not be expected to be adequately controlled by a herbicidal composition comprising both herbicides, which is not the case. Indeed, it has now been found that the combination of an HPPD-inhibiting herbicide and a triazine herbicide provides synergistic control of HPPD recalcitrant and triazine-resistant weeds.

Thus, according to the present invention there is provided a method of controlling a HPPD recalcitrant and triazine resistant weed at a locus, said method comprising applying to the locus a herbicidal composition comprising an HPPD-inhibiting herbicide and a triazine herbicide.

The term "locus" means the area in which the plants are growing or will grow. Thus the locus will typically be a field or fields. In the context of the present invention it should be understood that the locus may further comprise other weeds and/or crops such corn, cotton or soybeans.

It should be understood that the herbicidal composition can be applied as a pre- emergence application and/or a post-emergence application. In the context of the present invention, the term "post-emergence" is taken to mean that the herbicidal composition is applied once the HPPD recalcitrant and triazine resistant weed has emerged from the locus. The term "pre-emergence" is taken to mean that the herbicidal composition is applied before the HPPD recalcitrant weed has emerged from the locus. The HPPD-inhibiting herbicide and triazine herbicide may be applied sequentially to the locus (in any order). In this instance the components are typically applied within 3 days and most preferably within 24 hours of each other. Alternatively and preferably, the individual components are applied simultaneously in a single herbicidal composition.

Numerous HPPD-inhibiting herbicides are known in the art and include, for example, benzofenap, bicyclopyrone, benzobicyclon, isoxachlortole, isoxaflutole, mesotrione, pyrazoxyfen, pyrasulfatole, pyrazolynate, sulcotrione, tembotrione, topramazone and teiuryltrione. In the context of the present invention it is preferred that the HPPD-inhibiting herbicide used is selected from the group consisting of bicyclopyrone, isoxaflutole, mesotrione, tembotrione and topramezone. Mesotrione is particularly preferred. For the avoidance of doubt, the term HPPD-inhibiting herbicide should be taken to include agrochemically acceptable salts thereof, for example mesotrione can be in the form of a metal salt, for example a copper salt as disclosed in US 5,912,207.

The HPPD-inhibiting herbicide is typically applied from 20 g/ha to 500 g/ha. With regard to mesotrione the preferred post-emergence application rate is from 70 to 150 g/ha. Likewise, numerous triazine herbicides are known in the art. In the context of the present invention, the triazine herbicide is selected from the group consisting of ametryne, atrazine, cyanazine, desmetryne, dimethametryne, prometon, prometryne, propazine, terbumeton, terbuthylazine, terbutryne, trietazine, simazine, simetryne and metribuzin. In a preferred embodiment the triazine herbicide is selected from the group consisting of atrazine, metribuzin and terbuthylazine and is most preferably atrazine. The triazine herbicide is typically applied from 100 g/ha to 2000 g/ha, preferably from 500 g/ha to 1000 g/ha. In a particularly preferred embodiment of the present invention, the herbicidal composition comprises mesotrione and atrazine. The herbicidal composition may further comprise one or more additional herbicides and/or herbicide safeners in order to confer even better control of the HPPD recalcitrant and triazine resistant weed.

Examples of HPPD recalcitrant and triazine-resistant weeds can include biotypes of the following species:- Amaranthus sp. (in particular Amaranthus palmeri, Amaranthus rudis, Amaranthus tuberculatus and Amaranthus tamariscinus), Ambrosia sp., Conyza sp. Digitaria sp., Chenopodium sp. and Xanthium sp., Solanum sp., Datura sp., Abutilon sp, kochia, Russian thistle and Polygonum sp.

The components of the herbicidal composition as described above (whether administered sequentially or together) are suitable applied as an agriculturally acceptable composition. The composition(s) preferably also comprise an agriculturally acceptable carrier therefor. In practice, the composition is applied as a formulation containing the various adjuvants and carriers known to or used in the industry for facilitating dispersion. The choice of formulation and mode of application for any given compound may affect its activity, and selection will be made accordingly. The compositions of the invention may thus be formulated as granules, as wettable powders, as emulsifiable concentrates, as powders or dusts, as flowables, as solutions, as suspensions or emulsions, or as controlled release forms such as microcapsules. These formulations may contain as little as about 0.5% to as much as about 95% or more by weight of active ingredient. The optimum amount for any given compound will depend upon formulation, application equipment, and nature of the plants to be controlled.

Wettable powders are in the form of finely divided particles that disperse readily in water or other liquid carriers. The particles contain the active ingredient retained in a solid matrix. Typical solid matrices include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic solids. Wettable powders normally contain about 5% to about 95% of the active ingredient plus a small amount of wetting, dispersing, or emulsifying agent.

Emulsifiable concentrates are homogeneous liquid compositions dispersible in water or other liquid, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naphthas, isophorone and other non-volatile organic solvents. In use, these concentrates are dispersed in water or other liquid and normally applied as a spray to the area to be treated. The amount of active ingredient may range from about 0.5% to about 95% of the concentrate.

Granular formulations include both extrudates and relatively coarse particles, and are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, attapulgite clay, bentonite clays, montmorillonite clay, vermiculite, perlite and other organic or inorganic materials which absorb or which can be coated with the active compound. Granular formulations normally contain about 5% to about 25% active ingredients which may include surface-active agents such as heavy aromatic naphthas, kerosene and other petroleum fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins.

Dusts are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids that act as dispersants and carriers.

Microcapsules are typically droplets or granules of the active material enclosed in an inert porous shell which allows escape of the enclosed material to the surroundings at controlled rates. Encapsulated droplets are typically about 1 to 50 microns in diameter. The enclosed liquid typically constitutes about 50 to 95% of the weight of the capsule, and may include solvent in addition to the active compound. Encapsulated granules are generally porous granules with porous membranes sealing the granule pore openings, retaining the active species in liquid form inside the granule pores. Granules typically range from 1 millimeter to 1 centimeter, preferably 1 to 2 millimeters in diameter. Granules are formed by extrusion, agglomeration or prilling, or are naturally occurring. Examples of such materials are vermiculite, sintered clay, kaolin, attapulgite clay, sawdust and granular carbon. Shell or membrane materials include natural and synthetic rubbers, cellulosic materials, styrene- butadiene copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, polyureas, polyurethanes and starch xanthates. Other useful formulations for herbicidal applications include simple solutions of the active ingredient in a solvent in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene and other organic solvents. Pressurized sprayers, wherein the active ingredient is dispersed in finely-divided form as a result of vaporization of a low boiling dispersant solvent carrier, may also be used.

Many of these formulations include wetting, dispersing or emulsifying agents. Examples are alkyl and alkylaryl sulfonates and sulfates and their salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty amines. These agents, when used, normally comprise from 0.1% to 15% by weight of the formulation. Each of the above formulations can be prepared as a package containing the herbicide together with other ingredients of the formulation (diluents, emulsifiers, surfactants, etc.). The formulations can also be prepared by a tank mix method, in which the ingredients are obtained separately and combined at the grower site.

These formulations can be applied to the areas where control is desired by conventional methods. Dust and liquid compositions, for example, can be applied by the use of power-dusters, broom and hand sprayers and spray dusters. The formulations can also be applied from airplanes as a dust or a spray or by rope wick applications. To modify or control growth of germinating seeds or emerging seedlings, dust and liquid formulations can be distributed in the soil to a depth of at least one-half inch below the soil surface or applied to the soil surface only, by spraying or sprinkling. The formulations can also be applied by addition to irrigation water. This permits penetration of the formulations into the soil together with the irrigation water. Dust compositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as disking, dragging or mixing operations. Examples

Example 1

Field studies are conducted to evaluate the response of HPPD recalcitrant and triazine-resistant waterhemp to various post-emergence (POST) herbicide treatments.

Herbicide applications are applied at three post-emergence growth stages (2 inch, 6 inch and 11 inch). Mesotrione was applied at 105g/ha (lx), 210 g/ha and 420 g/ha as CALLISTO™. Atrazine was applied at 1120 g/ha as AATREX™. Plants are assessed for visual control (0% = no control, 100% = complete control) 19-22 days after application (DAA) of the herbicidal composition and the results are provided in Tables 1, 2 and 3 below. The expected scores indicated are determined according to Colby's formula (Colby, S. R. "Calculating synergistic and antagonistic responses of herbicide combinations", Weeds, 15, pp 20-22, 1967).

Table 1. Results 2 inch plants.

Table 2. Results 6 inch plants.

Table 3. Results 11 inch lants.

The results obtained indicate that, at all growth stages tested, the combination of mesotrione and atrazine provided synergistic control of the HPPD recalcitrant and triazine-resistant waterhemp.

Example 2 Field studies are conducted to evaluate the response of HPPD recalcitrant and triazine- resistant waterhemp to various post-emergence (POST) herbicide treatments. Herbicide applications are applied at post-emergence at approx. 2.5 inch. Mesotrione was applied at as CALLISTO™. Atrazine was applied at 1 120 g/ha as A AT REX™. Mesotrione + S- metolachlor + glyphosate was applied as HALEX-GT™. Plants are assessed for visual control (0% = no control, 100% = complete control) 26 days after application (DAA) of the herbicidal composition and the results are provided in Table 4 below.

Treatment Rate g/ha Visual Control (%)

Mesotrione 105 75

Mesotrione + 105 + 1120 91

Atrazine

Mesotrione + S- 105 + 1052 + 1052 96

metolachlor + + 1120

Glyphosate +

Atrazine

Claims

A method of controlling a HPPD recalcitrant and triazine-resistant weed at a locus, said method comprising applying to the locus a herbicidal composition comprising a HPPD-inhibiting herbicide and a triazine herbicide. A method according to claim 1, wherein the herbicidal composition is applied post- emergence. A method according to claim 1 or claim 2, wherein the HPPD-inhibiting herbicide is selected from the group consisting of benzofenap, bicyclopyrone, benzobicyclon, isoxachlortole, isoxaflutole, mesotrione, pyrazoxyfen, pyrasulfatole, pyrazolynate, sulcotrione, tembotrione, topramazone and tefuryltrione. A method according to claim 3, wherein the HPPD-inhibiting herbicide is selected from the group consisting of bicyclopyrone, isoxaflutole, mesotrione, tembotrione and topramezone. A method according to claim 4, wherein the HPPD-inhibiting herbicide is mesotrione. A method according to any one of the previous claims, wherein the application rate of the HPPD inhibiting herbicide is from 20 to 500 g/ha. A method according to any one of the previous claims, wherein the triazine herbicide is selected from the group consisting of ametryne, atrazine, cyanazine, desmetryne, dimethametryne, prometon, prometryne, propazine, terbumeton, terbuthylazine, terbutryne, trietazine, simazine, simetryne and metribuzin. A method according to claim 7, wherein the triazine herbicide is atrazine. A method according to claim 7 or 8, wherein the application rate of the triazine herbicide is from 100 g/ha to 2000 g/ha. A method according to any one of the previous claims, wherein the HPPD recalcitrant and triazine resistant weed is selected from the group consisting of Amaranthus sp., Ambrosia sp., Conyza sp. Digitaria sp., Chenopodium sp. and Xanthium sp., Solarium sp., Datura sp., Abutilon sp, kochia, Russian thistle and Polygonum sp.

1. A method according to claim 10, wherein the HPPD recalcitrant weed is Amaranthus palmeri and/or Amaranthus Rudis.