NZ754687A - Water-dispersible granules having high herbicide load - Google Patents

Abstract

A water-dispersible granule (WDG) composition of the herbicide terbutryn comprising at least 650 g/Kg terbutryn and an anionic polymeric dispersant selected from polycarboxylate dispersants, sulfonated polymers and mixtures thereof.

Description

Water-Dispersible Granules having High Herbicide Load Field This invention relates to water-dispersible granules containing the herbicide terbutryn. In particular the invention relates to water-dispersible granules that contain loadings of terbutryn that exceed 650g per kg of granules.

Background Terbutryn (2- tert- Butylaminoethylaminomethylthio-1,3,5-triazine) is a selective herbicide with pre-emergent and post-emergent activity. It acts by inhibiting photosynthesis and is classed as a group C herbicide. Terbutryn has been used to control grasses and annual broadleaf weeds in winter wheat, barley, sugarcane, sunflowers, peas and potatoes.

Terbutryn is a high melting point solid with poor solubility in many solvents making it problematic for certain types of formulation with high loadings.

Terbutryn has been sold under the trade names Terbutryn 500 SC (4 Farmers), Apparent Terbutryn 500 SC (Apparent), Conquest Terbo 500 SC (Conquest Crop protection), Crop Care Igran Flowable Liquid (Crop Care Australia), Farmalinx Terbutryn 500 SC (Farmalinx), Justice Herbicide (Sipcam Pacific Australia), Ozcrop Terbutryn 500 SC (Ozcrop), Rainbow Terbutryn 500 SC (Shandong Rainbow International Co), Salvation Herbicide (FMC Australasia), Terbutrex herbicide (Adama Australia), Titan Terbutryn 500 SC Titan Ag. All of the above terbutryn formulations are 500 g/L suspension concentrates.

It would be desirable to provide a water-dispersible granule containing high loadings of terbutryn to achieve a higher level of herbicidal activity per unit weight of product and reduce the cost and improve convenience of packaging, storage, transport and handling.

Summary We have found that certain dispersants and optionally a surfactant wetting agent allows granules of high loading of terbutryn to be achieved and yet provide efficient dispersion in water prior to application in control of weeds.

There is provided a water-dispersible granule (WDG) composition comprising at least about 650 g/kg of terbutryn (preferably at least about 700 g/Kg, more preferably at least about 750 g/kg) and further comprising at least one anionic polymeric dispersant selected from polycaboxylate dispersants, polysulfonate dispersants (particularly sulfonated aromatic-formaldehyde condensation polymers and their salts) and mixtures thereof and optionally at least one further anionic surfactant.

The composition may, and preferably will, comprise a filler.

In one embodiment, the anionic dispersant comprises a polycarboxylate.

Polycarboxylates include (meth)acrylate polymers, and polymers of diacid or diacid derivatives such as copolymers of the unsaturated diacid or diacid derivatives with linear or branched alkenes. Examples of the polycarboxylates may be selected from poly(meth)acylate and copolymers thereof and salts thereof, maleic anhydride copolymers and salts thereof and succinic anhydride copolymers and salts thereof.

Preferred polycarboxylates include sodium, amine and ammonium salts of polymers selected from poly(meth)acrylic acid, (meth)acrylic / (meth)acrylamide copolymer, copolymers of maleic anhydride with linear or branched alkenes and acrylic / lauryl (meth)acrylate copolymer.

The dispersant may, in a further embodiment, be selected from sulfonated aromatic-formaldehyde condensation polymers and salt thereof. Preferred examples of sulfonated aromatic-formaldehyde condensation polymers include sulfonates of polymers of one or more aromatics selected from phenol, alkyl phenol, naphthalene and alkylnapthalene. The polymers may be formaldehyde condensates such as sulfonates of naphthalene formaldehyde condensates and salts thereof, sulfonates of alkylnaphthalene formaldehyde condensates and salts thereof, sulfonates of phenol derived formaldehyde condensates and sulfonates of alkylphenol derived formaldehyde condensates. The preferred polysulfonate dispersants are salt of polymerised alkylnaphthalene sulfonic acid. The salt is typically a alkali metal salt, amine or ammonia salt and preferably is the sodium salt.

In the most preferred embodiment the dispersant comprises each of the polycarboxylate and polysulfonate type dispersants.

The anionic dispersant is typically present in an amount of at least 20 g/Kg such as at least 30 g/Kg, at least 40g/Kg or at least 50g/Kg. Typically the anionic dispersant is present in an amount of no more than about 150g/Kg such as not more than 120 g/Kg, no more than 100 g/Kg, preferably 30g/Kg to 150 g/Kg, more preferably in the range 40 to 150 g/Kg, still more preferably 40 g/Kg to 100 g/Kg of WDC composition.

Detailed Description The term "(meth)acrylate" refers to acrylate and/or methacrylate. The term “(meth)acrylamide” refers to acrylamide and/or methacrylamide.

The term polymer includes homopolymers and copolymers. The term polymer includes oligomers. Polymers contain at least 2 monomeric units, preferably at least three monomeric units.

A dispersant is a substance which adsorbs onto the surface of particles and helps to preserve the state of dispersion of the particles and prevents them from aggregating. Dispersants are added to agrochemical compositions to facilitate dispersion and suspension during manufacture, and to ensure the particles redisperse into water in a spray tank.

Throughout the description and the claims of this specification the word “comprise” and variations of the word, such as “comprising” and “comprises” is not intended to exclude other additives, components, integers or steps.

The dispersant provides a stable WDG composition with a high loading of terbutryn which can efficiently be dispersed in water, such as in a spray tank, for application to weeds for post-emergent weed control and/or to soil in which pre- emergent control is required.

The amount (loading) of terbutryn in the WDG composition is at least about 650 g/kg of terbutryn (preferably at least about 700 g/Kg, more preferably at least about 750 g/kg). The loading of terbutryn may be up to 900 g/Kg such as up to 850 g/Kg or up to 800 g/Kg with the preferred range being 650 g/Kg to 850 g/Kg such as 700 g/Kg to 850 g/Kg or 750 g/Kg to 850 g/Kg.

The WDG composition comprises at least one anionic polymeric dispersant selected from the group consisting of polycaboxylate dispersants and polysulfonate dispersants.

In one embodiment, the anionic dispersant comprises a polycarboxylate.

Polycarboxylates include (meth)acrylate polymers, and polymers of diacid or diacid derivatives such as copolymers of the unsaturated diacid or diacid derivatives with linear or branched alkenes. Examples of the polycarboxylates may be selected from poly(meth)acylate and copolymers thereof and salts thereof, maleic anhydride copolymers and salts thereof and succinic anhydride copolymers and salts thereof.

Preferred polycarboxylates include sodium, amine and ammonium salts of polymers selected from poly(meth)acrylic acid, (meth)acrylic / (meth)acrylamide copolymer, copolymers of maleic anhydride with linear or branched alkenes and acrylic / lauryl (meth)acrylate copolymer. Polycarboxylates include acrylic and methacrylic acid polymers, and reaction products of unsaturated diacid or diacid derivatives (such as maleic anhydride and succinic anhydride) and linear or branched alkenes. Examples of such copolymers include olefin (such as isobutylene or diisobutylene) succinic anhydride copolymers and salts thereof, olefin (such as isobutylene or diisobutylene) – maleic anhydride polymers and their salts and styrene-maleic anhydride copolymers and their salts where, for example, the salts may be formed with alkali metals, ammonia or amines.

Such polycarboxylates may, for example, have a molecular weight (Mn) in the range of about 150 to about 70,000 g/mole, preferably 600 to 12,000 g/mole.

The polycarboxylate dispersant may be present in an amount of up to 100g/Kg such as up to 80 g/Kg. In embodiments where the polycarboxylate dispersant is present the amount is typically at least 10 g/Kg such as at least 20 g/Kg, at least 20 g/Kg or at least 40g/Kg. The preferred compositions containing both polycarboxylate and polysulfonate dispersants typically comprise from 20 g/Kg to 100 g/Kg of the polycarboxylate dispersant such as from 20 g/Kg to 80 g/Kg or 30 g/Kg to 80 g/Kg.

The composition may, and preferably will comprise a dispersant which is selected from polysulfonates such as sulfonated aromatic-formaldehyde condensation polymers and their salts. Preferred examples of such polysulfonate dispersants include sulfonates of polymers of one or more of phenol, alkylphenol, naphthalene, and alkylnapthalene. The polymers are typically formaldehyde condensates such as sulfonates of naphthalene-formaldehyde condensates and salts thereof, sulfonates of alkylnaphthalene-formaldehyde condensates and salts thereof, sulfonates of phenol- formaldehyde condensates and salts thereof, and sulfonates of alkylphenol- formaldehyde condensates and salts thereof. The preferred polysulfonate dispersants are salts of sulfonated naphthalene-formaldehyde condensates, salts of sulfonated alkylnaphthalene-formaldehyde condensates and mixtures thereof. The salt is typically a alkali metal salt, an amine salt or ammonia salt and preferably is the sodium salt. The mean molecular weight of these materials can typically range from about 300 to about 15,000 g/mole, preferably about 500 to about 10,000 g/mole.

The component selected from the group consisting of sulfonated naphthalene-formaldehyde condensates, sulfonated alkylnaphthalene-formaldehyde condensates and sulfonated phenol-formaldehyde condensates, sulfonated alkylphenol (e.g. cresol)-formaldehyde condensates include aromatic groups in which the alkyl group may be a C to C alkyl substituent such as methyl or butyl group.

Specific commercial sources of suitable sulfonate surfactants include sodium sulfonate of alkylnaphthalene formaldehyde condensates such as MORWET D425 (available from Witco), LOMAR PW (available from Henkel, Ambler, Pennsylvania) and DARVAN 1(available from R.T. Vanderbilt Co., Norwalk, Connecticut) being most preferred.

In a preferred embodiment the WDG composition comprises a polycarboxylate dispersant and a sulfonated aromatic-formaldehyde condensate dispersant.

The sulfonated aromatic-formaldehyde condensate dispersant may be present in an amount of up to 100g/Kg such as up to 80 g/Kg. In embodiments where the polysulfonate dispersant is present the amount is typically at least 10 g/Kg such as at least 20 g/Kg. The preferred compositions containing both polycarboxylate and polysulfonate dispersants typically comprise from 10 g/Kg to 80g/Kg of the polysulfonate dispersant (most preferably alkylnaphthalene sulfonate-formaldehyde condensate) such as from 20 g/Kg to 80 g/Kg or 20 g/Kg to 60 g/Kg.

The WDG composition preferably contains an anionic surfactant which acts as a wetting agent in the composition and also aids in dispersion of the active terbutryn. The anionic surfactant may include at least one selected from the group consisting of (a) sulfonates: fatty alcohol ether sulfonates, fatty acid sulfonates, alkylbenzenesulfonates, alkyl naphthalene sulfonates, alkylaryl sulfonates, olefin sulfonates and alkylphenol ethoxylate sulfonates; (b) sulfates: alkylsulfates and alkyl ether sulfates (c) phosphates: phosphates of fatty alcohol ethoxylate, and phosphates of alkylphenol ethoxylate having 4 to 12 EO units; (d) sulfosuccinate esters: alkyl sulfosuccinates; (e) carboxylates, alkylphenol ethoxylate carboxylates. The preferred anionic surfactant wetting agents are sulfonates, particularly, alkylaryl sulfonates such as alkylbenzenesulfonates, alkyl naphthalene sulfonates and mixtures thereof and most preferably the anionic surfactant wetting agent is a salt of alkylbenzene sulfonate such as sodium dodecylbenzene sulfonate. Specific examples include sodium dodecyl-benzenesulfonate or sodium tridecyl-benzenesulfonate.

The surfactant wetting agent may be present in an amount of at least g/Kg such as at least 10 g/Kg or at least 15 g/Kg. In one set of embodiments the anionic surfactant wetting agent is present in an amount of up to 80 g/Kg such as up to 60 g/Kg, up to 40 g/kg or up to 40 g/Kg. In specific embodiments the anionic surfactant wetting agent is present in an amount of 5 g/Kg to 80 g/Kg such as 10 g/Kg to 60 g/Kg, 15 g/Kg to 60 g/Kg or 15 g/Kg to 40 g/Kg.

In one embodiment the WDG composition comprises a polycarboxylate- type dispersant and an anionic surfactant wetter.

In a further embodiment the WDG composition comprises a sulfonated aromatic-formaldehyde condensate dispersant and an anionic wetter.

In the more preferred embodiment the WDG composition comprises a polycarboxylate-type dispersant and a sulfonated aromatic-formaldehyde condensate type dispersant and an anionic surfactant wetter. In this embodiment the cumulative amount of polycarboxylate-type dispersant, sulfonated aromatic-formaldehyde condensate dispersant and anionic dispersant is no more than about 150 g/kg such as no more than 120 g/Kg of WDG. Typically the cumulative amount of polycarboxylate-type dispersant, sulfonated aromatic-formaldehyde-condensate dispersant and anionic surfactant wetting agent is more than about 70 g/kg.

In embodiments where both polycarboxylate and polysulfonate dispersants are present the composition has a weight ratio of the polycarboxylate- type dispersant to the sulfonated aromatic-formaldehyde condensate type dispersant of, for example 1:5 to 5:1 such as 1:2 to 5:1 or 1:1 to 3:1. The ratio of total polycarboxylate-type dispersant and sulfonated aromatic-formaldehyde condensate type dispersant to the anionic surfactant may, for example be from 10:1 to 1:1 such as :1 to 2:1.

The water-dispersible granules may further comprise finely divided filler materials such as minerals and in particularly inert clay particles. Specific examples of filler materials include one or more selected from the group consisting of silicon dioxide, gums, insoluble metal oxides, mineral earths, bentonite, perlite, talc, kaolin, aluminium silicate, diatomaceous earth, attapulgite, barium sulfate, mica, gums such as polysaccharide gums, calcium carbonate, fused sodium potassium, precipitated silicates, aluminium silicate, zeolites and mixtures thereof. Phyllosilicate filler is particularly preferred as such materials comprise sheets of silicate tetrahedra and in finely divided form to provide an effective carrier for the herbicide. Particularly preferred examples of the phyllosilicate filler materials include kaolin, attapulgite, montmorillonite and talc and kaolin is particularly preferred. The finely divided filler material is preferably present in an amount of 20 g/kg to 200 g/kg of WDG composition. In one embodiment we have found to be useful the composition comprises kaolin clay in an amount of 20 g/Kg to 200 g/kg preferably 40g/Kg to 150g/Kg such as 80 g/Kg to 150 g/Kg of WDG composition.

In one embodiment the WDG composition comprises: 650 g/Kg to 900 g/Kg (preferably 700 g/Kg to 850 g/Kg) terbutryn; g/Kg to 100 g/Kg (preferably 20 g/Kg to 80 g/Kg) sodium polycarboxylate polymeric dispersant; 10g/Kg to 80 g/Kg (preferably 15g/Kg to 60 g/Kg) Sodium salt of sulfonated aromatic-formaldehyde condensation polymers; g/Kg to 80 g/Kg (preferably 10 g/Kg to 60 g/KG) alkylbenzene sulfonate surfactant wetting agent; and 40g/Kg to 150g/Kg phyllosilicate filler.

The WDG composition will typically comprise granules having a minimum dimension in the range of from 1mm to 5 mm. The aspect ratio (maximum/minimum dimension) of the granules is typically from 1 to 10, preferably 1 to 5.

In a further aspect the invention provides a process for preparation of terbutryn WDG composition comprising forming an finely divided mixture of the components as herein described, optionally with milling; adding water, preferably as a spray, to the finely divided mixture to form an extrudable wet mixture of the composition; extruding the wet mixture to form an extrudate; fragmenting the extrudate, for example by cutting or tumbling the extrudate to form wet granules; and optionally drying the wet granules at elevated temperature, typically at least °C such as 30°C to 70°C.

In a further embodiment the invention provides a method of pre-emergent or post emergent control of weeds comprising dispersing the WDG composition hereinbefore described in water to form an aqueous dispersion of the tebutryn herbicidal composition in water; and applying the aqueous dispersion of the tebutryn herbicidal composition in water to the locus at which pre-emergent or post-emergent weed control is desired.

In field trials it has been found that the WDG formulation of high loading such as 750 g/Kg results in less damage (e.g. chlorosis and stunting) to certain crops, for example green pea crops, than corresponding suspension concentrates (500 g/L) applied at the same active rate.

The invention will now be described with reference to the following examples. It is to be understood that the examples are provided by way of illustration of the invention and that they are in no way limiting to the scope of the invention.

EXAMPLES Example 1 – Composition Example (In the following Examples, the Example 1 composition is designated Terbutryn 750 g/kg WDG) The composition of Example 1 shown in Table 1 was made into granules using the formulation process described.

Table 1 Purpose in Constituent Name CAS Concentration Formulation Terbutryn technical 97% 8860 773.2 g/kg active suffice to give 750 g/kg active Sodium polycarboxylate 371998 50.0 g/kg dispersant (GEROPON T/36) Sodium naphthalene- sulfonic acid, polymer 90844 30.0 g/kg dispersant with formaldehyde (DARVAN 1) Sodium dodecylbenzene .0 g/kg 251550 wetter sulfonate Kaolin (balance to 1 kg) 13327 126.8 g/kg filler DARVAN 1” (sodium salt of a sulfonated naphthalene - formaldehyde condensate polymer, a product of R.T. Vanderbilt Co. Inc.), Formulation Process Terbutryn technical grade and non-active constituents are first mixed or compounded in a vessel, followed by micronization in a jet air mill afterward until it forms fine powder at desirable particle size distribution and homogeneity. Fine powder come out of jet air mill is gravitationally fed into a clean and dry vessel.

Water is sprayed to form a ‘dough’ (semi-solid) with an assistance by continuous blending. The dough is then charged into a pressurised twin screw extruder where product discharged through the sieve screen at a predetermined diameter is cut off at regular intervals to become granules. Granules are dried in a heating chamber monitored at 60˚C coupling with partial vacuum for 2 hours. Further drying is carried out in a fluidized bed at 60˚C as temperature to last for 45 minutes. Moisture levels are settled at below 3%. The dried granules are subject to sieving to remove any dust or non-compliant sized particles. Batch size is designed for ±2000 Kg.

Quality Control Micronization – in dry phase prior to compounding - minimum 98% through 37 μm sieve - 100% through 43 μm sieve - pH (1% aqueous suspension) ±7.5 Bulk density - > 70 gram / 100 mL (wet granule) - > 55 gram / 100 mL (dry granule) Sampling Sample is withdrawn at the completion of the final formulation stage for every production batch prior to packaging.

Product Specification Release and Expiry Specifications for the Terbutryn 750 g/Kg WDG herbicide granules were as reported in Table 2.

Table 2 - Release Specification Test Parameter Standard Test Method off-white to beige Appearance Visual extruded granule Active content, w/w 750 ± 25 g/Kg CIPAC *212/1/M/1.5 pH (1% aq. suspension) 6.0 ~ 9.0 CIPAC MT 75.3 Wettability ≤ 60 seconds CIPAC MT 53.3.1 Suspensibility ≥ 75.0% CIPAC MT168 Degree of Dispersion ≥ 70.0% CIPAC MT174 Persistent foam ≤ 60.0 mL CIPAC MT 47.2 Dustiness ≤ 0.5% CIPAC MT 171 Water Content ≤ 3.0% CIPAC MT30.1 Particle Size ≥ 98.0% CIPAC MT185 (thru 75 µm sieve) Bulk Density (gram/cm ) 0.55 ~ 0.65 CIPAC MT169 Attrition Resistance ≤ 2.0% CIPAC MT178.2 (residue on 125 µm sieve) Flowability (5 liftings & nil CIPAC MT172 residue on 4.75 mm sieve) Stability Studies - Summary of Stability Study 250 gram of Terbutryn 750 g/kg WDG sample contained in a 500 mL HDPE jar was subject to accelerated storage at (54±2)ºC for 14 days. No physical change was found in the material after the studying period.

A similar stability study was conducted with a sample size at 272 gram contained in a 500 mL HDPE container. The container was placed into an oven that was temperature controlled at (54±2)°C for 14 days. Physical parameters were measured for samples withdrawn both before and after the accelerated storage and reported. No physical change was noticeable due to the accelerated storage.

Bioefficacy Study S1 A field trial was conducted in Tasmania, Australia to evaluate the bioequivalence of Terbutryn 750 WG (subject of this invention) with Terbutryn 500 SC for the control of broadleaf weeds in green peas cv. Ashton (i.e. variety Ashton).

Treatments included Terbutryn 750 WG (subject of this invention) and Terbutryn 500 SC (commercial standard, Igran as sold by Nufarm Australia) each applied at 375, 500, 1000 g ai/ha and an untreated control. Treatments were applied as a single foliar application to actively growing weeds in a spray volume of 100 L/ha using nozzles which produced a coarse spray quality.

Broadleaf weed species present across the trial site at the time of application included blackberry nightshade (Solanum nigrum) at the 2 leaf growth stage, fat hen (Chenopodium album) at the 2-4 leaf growth stage and wild radish (Raphanus raphanistrum) at the 8-9 or more leaf growth stage. Knockdown weed control was assessed at 8 days after application (DAA), 15 and 28DAA.

Terbutryn 750 WG was slower acting against blackberry nightshade with significantly lower brownout at 8DAA however, by 15DAA formulations were equivalent in their effect on blackberry nightshade.

Based on the measure of weed count per square meter, formulation 750 WG displayed substantially the same efficacy as formulation Terbutryn 500 SC in controlling blackberry nightshade (Solanum nigrum), fat hen (Chenopodium album) and wild radish (Raphanus raphanistrum).

The highest rate, 1000 g ai/ha, of both products was more effective in the control of weeds than the lower rates 350 and 500 g ai/ha.

Phytotoxic symptoms, including stunting and chlorosis of green peas were evident for Terbutryn 500 SC when applied at 500 and 1000 g ai/ha. Conversely, Terbutryn 750 WG appeared safe at all rates (350, 500, and 1000 g ai/ha) when applied to green peas at the 6 node crop stage.

Bioefficacy Study S2: Summary In Victoria, Australia a field trial was conducted to evaluate Terbutryn 750 WG for the control of sowthistle (Sonchus oleraceus) and fumitory (Fumaria densiflora) in wheat c.v. Kord CL Plus. Terbutryn 750 WG applied at 275, 425 and 850 g ai/ha was compared to the registered formulation Terbutryn 500 SC at equivalent three rates and an untreated control. Herbicide treatments were applied once at BBCH 25-31 growth stage of the crop when the fumitory and sowthistle were at the 8-10cm rosette growth stage as a broadcast foliar spray, with a boom sprayer fitted with flat fan nozzles in a spray volume of 97 L/ha.

Crop safety and weed efficacy was visually assessed at 14, 28 and 42 days after application (DAA).

Both Terbutryn 750 WG and Terbutryn 500 SC were safe to wheat, with no symptoms of phytotoxicity observed up to 42DAA (days after application).

All herbicide treatments provided significant control of fumitory and sowthistle at 14, 28 and 42DAA. The 425 and 850 g ai/ha rates provided significantly greater control of both fumitory and sowthistle for both formulations of Terbutryn.

Terbutryn 750 WG was bioequivalent to Terbutryn 500 SC for control of sowthistle and fumitory at 14, 28 and 42DAA.

Crop Safety Study S3: Green Pea Crop SafetyData on chlorosis and stuting in the green pea experiment described in Bioefficacy study 1 above is provided in Table 3.

Table 3 - Green Pea crop safety No Treatment Rate (g ai/ha) Chlorosis and stunting (% area) 8DAA 1 Terbutryn 750 WG 375 0 c 2 Terbutryn 750 WG 500 0 c 3 Terbutryn 750 WG 1000 0 c 4 Terbutryn 500 SC 375 0 c Terbutryn 500 SC 500 5 b 6 Terbutryn 500 SC 1000 12 a 7 Untreated control Nil 0 c It is noteworthy that at the lowest rate (375g ai/ha) no chlorosis or stunting were found with either formulation Terbutryn 750 WG (subject of this invention) or with formulation Terbutryn 500 SC (prior art standard commercial product old as Igran by Nufarm Australia). By contrast, chlorosis and stunting with Terbutryn 750 WG were significantly less than with Terbutryn 500 SC at all other rates (500 and 1000 g ai/ha).

Bioefficacy, stability and co-formulation Study S4: Summary In Tasmania in 2017, a field trial was conducted to evaluate Terbutryn 750 WG for crop safety in green peas cv. Resal. Treatments included:  Terbutryn (750 g/kg terbutryn), subject of the invention, applied solo at 500 g ai/ha,  Terbutryn (750 g/kg terbutryn) subject of the invention at either 375 g ai/ha or 500 g ai/ha, each in a tank mixture with Bentazone 480 SL (480 g/L bentazone) at 720 g ai/ha,  Igran 500 SC (500 g/L terbutryn, sold by Nufarm) at 375 g ai/ha in a tank mixture with Bentazone at 720 g ai/ha,  Terbutryn (750 g/kg terbutryn), subject of the invention at 375 g ai/ha in a tank mixture with MCPA 250 (250 g/L MCPA present as the sodium and potassium salt) at 100 g ai/ha and either Bentazone at 720 g ai/ha or Mentor 750 WG (750 g/kg metribuzin) at 165 g ai/ha,  Terbutryn (750 g/kg terbutryn), subject of the invention at 225 g ai/ha in a tank mixture with Bentazone at 960g ai/ha and MCPA 250 at 100 g ai/ha,  Bladex 900 WG (900 g/kg cyanazine) at 450 g ai/ha in a tank mixture with Bentazone at 720 g ai/ha and MCPA 250 at 100 g ai/ha, and  an untreated control.

Treatments were applied as a single broadcast foliar application to green peas at the BBCH 33-34 (3-4 visibly extended internodes, 4-5 node) crop stage using a backpack sprayer fitted with Agrotop AirMix 110-01 air inducted flat fan nozzles in a spray volume of 180 L/ha.

Green pea biomass was assessed at 7 days after application (7DAA), 14DAA and 28DAA. Necrosis of green pea foliage was assessed at 7DAA and normalised difference vegetation index (NDVI) at 28DAA.

All herbicide treatments significantly reduced green pea biomass at 7DAA by 5-36%, decreased to a 3-21% biomass reduction for terbutryn treatments at 14DAA; biomass for Bladex + Bentazone + MCPA 250, the only treatment not including the active ingredient terbutryn, was equivalent to the untreated control. At the final assessment timing, Terbutryn (750 g/kg) + Bentazone + MCPA 250 at 375 + 720 + 100 g ai/ha and Terbutryn (750 g/kg) + Mentor + MCPA 250 were the only treatments with biomass significantly lower than the untreated control.

At 7DAA, significant necrosis was seen on green pea leaves of plants treated with Igran + Bentazone (24% leaf area affected) or Terbutryn (750 g/kg) + Mentor + MCPA 250 (55% leaf area), compared with 0-8% leaf area affected for all other herbicide treatments. Necrosis seemed to be restricted to the lower leaves emerged at the time of treatment application, and no further necrotic symptoms were seen on new growth. At 28DAA, NDVI, a measure of whole plot greenness, was equivalent for all treatments.

The addition of Bentazone at 720 g ai/ha to Terbutryn 750 g/kg at 500 g ai/ha significantly increased necrosis and reduced biomass compared with Terbutryn (750 g/kg) applied solo at 500 g ai/ha.

Terbutryn 750 g/kg ( at 375 g ai/ha) + Bentazone was safer than Igran (terbutryn 500 SC at 375 g ai/ha) + Bentazone, with higher biomass and less necrosis of green pea leaves.

The addition of MCPA 250 to the tank mixture of Terbutryn (750 g/kg) at 375 g ai/ha + Bentazone at 720 g ai/ha reduced green pea biomass.

Crop safety was equivalent for the tank mixtures of Terbutryn (750 g/kg) at 375 g ai/ha + Bentazone at 720 g ai/ha + MCPA 250 and Terbutryn (750 g/kg) at 225 g ai/ha + Bentazone at 960 g ai/ha + MCPA 250.

The tank mixture of Terbutryn (750 g/kg) + Bentazone + MCPA 250 was safer to green peas than Terbutryn (750 g/kg) + Mentor + MCPA 250, at equivalent application rates of Terbutryn (750 g/kg) and MCPA 250, with numerically and sometimes significantly higher biomass and less necrosis of lower, younger leaves.

The addition of Bladex to the tank mixture of Bentazone at 720 g ai/ha + MCPA 250 was safer than Terbutryn (750 g/kg)+ Bentazone (720 g ai/ha) + MCPA 250, with significantly higher biomass at 7DAA and 14DAA and significantly less early necrosis of green pea leaves.

MATERIALS AND METHODS Table 4 - Products The products and treatments examined are listed in Tables 4 and 5 respectively.

Active Concentration Product name ingredient of active Formulation (ai) ingredient Terbutryn 750 WG Water dispersible terbutryn 750 g/kg Subject of invention granule Bentazone 480 SL bentazone 480 g/L Soluble concentrate Suspension Igran 500 SC terbutryn 500 g/L concentrate MCPA present as MCPA 250 the sodium and 250 g/L Liquid concentrate potassium salt Water dispersible Mentor 750 WG metribuzin 750 g/kg granule Water dispersible Bladex 900 WG cyanazine 900 g/kg granule Table 5 - Treatments Rate No. Product Application schedule Active Product ingredient (mL or g/ha) (g ai/ha) 1 Untreated control Nil Nil N/A Single broadcast foliar 2 Terbutryn 750 WG 667 g 500 application to green peas Terbutryn 750 WG 667 g 500 at the BBCH 33-34 (3-4 Bentazone 480 SL 1500 mL 720 visibly extended Terbutryn 750 WG 500 g 375 internodes, 4-5 nodes) Bentazone 480 SL 1500 mL 720 crop stage.

Igran 500 SC 750 mL 375 Treatments applied using Bentazone 480 SL 1500 mL 720 a backpack sprayer fitted Terbutryn 750 WG 500 g 375 with Agrotop AirMix 110- 6 Bentazone 480 SL 1500 mL 720 01 air inducted flat fan MCPA 250 400 mL 100 Terbutryn 750 WG 300 g 225 nozzles in a spray volume 7 Bentazone 480 SL 2000 mL 960 of 180 L/ha.

MCPA 250 400 mL 100 Terbutryn 750 WG 500 g 375 8 Mentor 750 WG 220 g 165 MCPA 250 400 mL 100 Bladex 900 WG 500 g 450 9 Bentazone 480 SL 1500 mL 720 MCPA 250 400 mL 100 Table 6 - Chronology of events Days after Crop stage Date application Event BBCH scale Description (DAA) 3-4 visibly extended 23/11/17 0 33-34 internodes (4-5 Application A nodes) 7 side shoots and 5 Biomass assessment /11/17 7 27/35 visibly extended Necrosis assessment internodes 9 side shoots and 6 07/12/17 14 29/36 visibly extended Biomass assessment internodes % of pods have Biomass assessment 21/12/17 28 72 reached typical length NDVI assessment Table 7 - Green pea biomass at 7DAA, 14DAA and 28DAA Green pea biomass (mean % relative to the untreated control) Rate No. Treatment (g ai/ha) 7DAA 14DAA 28DAA /11/17 07/12/17 21/12/17 1 Untreated control Nil 100 a 100 a 100 a 2 Terbutryn 750 WG 500 90 bcd 96 bc 100 a Terbutryn 750 WG 500 3 85 cde 89 def 98 ab Bentazone 480 SL 720 Terbutryn 750 WG 375 4 95 b 97 bc 99 ab Bentazone 480 SL 720 Igran 500 SC 375 73 ef 79 f 95 ab Bentazone 480 SL 720 Terbutryn 750 WG 375 Bentazone 480 SL 720 80 de 87 de 95 bc MCPA 250 100 Terbutryn 750 WG 225 90 bcd 92 cd 96 ab Bentazone 480 SL 960 MCPA 250 100 Terbutryn 750 WG 375 8 Mentor 750 WG 165 64 f 85 ef 86 c MCPA 250 100 Bladex 900 WG 450 720 95 bc 99 ab 99 ab 9 Bentazone 480 SL MCPA 250 100 P-value 0.0001 0.0001 0.0080 LSD (P ≤ 0.05) tA tA tA Means followed by the same letter are not significantly different (P = 0.05, LSD) DAA = Days after application tA = Original plot means are presented with analysis of variance and letters of separation from data transformed using y = Arcsine square root percent (x).

CONCLUSIONS All herbicide treatments caused a significant early reduction of green pea cv. Resal biomass by 5-36%. A signficant reduction in biomass was seen for all terbutryn treatments at 14 days after application.

At the final assessment timing (28 days after application), Terbutryn + Bentazone +MCPA 250 at 375 + 720 + 100 g ai/ha and Terbutryn + Mentor + MCPA 250 were the only treatments with biomass significantly lower than the untreated control.

Significant early necrosis was seen on green pea leaves of plants treated with Igran + Bentazone (24% leaf area affected) or Terbutryn + Mentor + MCPA 250 (55% leaf area affected). Necrosis seemed to be restricted to the lower leaves emerged at the time of treatment application, and no further necrotic symptoms were seen on new growth.

Normalised difference vegetation index (NDVI), a measure of whole plot greenness, was equivalent for all treatments.

The addition of Bentazone at 720 g ai/ha to Terbutryn at 500 g ai/ha significantly increased necrosis and reduced biomass compared with Terbutryn applied solo at 500 g ai/ha.

Terbutryn (terbutryn at 375 g ai/ha) + Bentazone was safer than Igran (terbutryn at 375 g ai/ha) + Bentazone. This is evident from a comparison of treatments 4 and 5 at 7 and 14 DAA in tables of Green pea biomass (above) and Green pea necrosis (below).

The addition of MCPA 250 to the tank mixture of Terbutryn at 375 g ai/ha + Bentazone at 720 g ai/ha reduced green pea biomass.

Crop safety was equivalent for the tank mixtures of Terbutryn at 375 g ai/ha + Bentazone at 720 g ai/ha + MCPA 250 and Terbutryn at 225 g ai/ha + Bentazone at 960 g ai/ha + MCPA 250.

The tank mixture of Terbutryn + Bentazone + MCPA 250 was safer to green peas than Terbutryn + Mentor + MCPA 250, at equivalent application rates of Terbutryn and MCPA 250.

The addition of Bladex to the tank mixture of Bentazone at 720 g ai/ha + MCPA 250 was safer than Terbutryn + Bentazone (720 g ai/ha) + MCPA 250.

Table 8 - Green pea necrosis and NDVI Green pea necrosis Green pea NDVI (% leaf area affected) (0-1) Rate No. Treatment (g ai/ha) 7DAA 28DAA /11/17 21/12/17 1 Untreated control Nil 0 e 0.74 2 Terbutryn 750 WG 500 1 de 0.72 Terbutryn 750 WG 500 3 8 c 0.72 Bentazone 480 SL 720 Terbutryn 750 WG 375 4 3 de 0.73 Bentazone 480 SL 720 Igran 500 SC 375 24 b 0.70 Bentazone 480 SL 720 Terbutryn 750 WG 375 Bentazone 480 SL 720 3 d 0.70^ MCPA 250 100 Terbutryn 750 WG 225 7 Bentazone 480 SL 960 1 de 0.73 MCPA 250 100 Terbutryn 750 WG 375 8 Mentor 750 WG 165 55 a 0.70 MCPA 250 100 Bladex 900 WG 9 Bentazone 480 SL 720 0 e 0.73 MCPA 250 P-value 0.0001 0.1395 LSD (P ≤ 0.05) tA NSD Means followed by the same letter are not significantly different (P = 0.05, LSD) DAA = Days after application NDVI = Normalised difference vegetation index tA = Original plot means are presented with analysis of variance and letters of separation from data transformed using y = Arcsine square root percent (x) NSD = No significant difference due to a P-value > 0.05 ^ Treatment has been excluded from statistical analysis to correct for heterogeneity of variance/skewness/kurtosis.

Claims (25)

1. A water-dispersible granule (WDG) composition of the herbicide terbutryn comprising at least 650 g/Kg terbutryn and an anionic polymeric dispersant selected from polycarboxylate dispersants, sulfonated polymers and mixtures thereof.

2. The WDG composition of claim 1, wherein the anionic dispersant comprises a polycarboxylic acid dispersant selected from poly(meth)acylate and copolymers thereof and salts thereof, maleic anhydride copolymers and salts thereof and succinic anhydride copolymers and salts thereof.

3. The WDG composition of claim 1 or claim 2, wherein the dispersant comprises a salt of a sulfonated aromatic-formaldehyde condensation polymer wherin the aromatic group is selected from a naphthalene, alkylnaphthalene, phenol and alkylphenol.

4. The WDG of any one of the previous claims, wherein the anionic polymeric dispersant comprises a sulfonated aromatic-formaldehyde condensation polymer in the form of the sodium salt.

5. The WDG of any one of the previous claims, wherein the anionic polymeric dispersant comprises a mixture of polycarboxylate dispersant and sulfonated aromatic-formaldehyde condensation polymer.

6. The WDG of any one of the previous claims, wherein total anionic dispersant selected from polycarboxylate dispersants, sulfonated polymers and mixtures thereof in an amount of no more than 150 g/Kg, preferably from 40 g/Kg to 150 g/Kg, still more preferably 40 g/Kg to 100 g/Kg.

7. The WDG of any one of the previous claims, wherein the polycarboxylate dispersant is present in an amount of up to100 g/Kg, preferably 20 g/Kg to 100 g/Kg, more preferably, still more preferably 20 g/Kg to 80 g/Kg, most preferably 30 g/Kg to 80 g/Kg.

8. The WDG of any one of the previous claims, wherein the sulfonated aromatic- formaldehyde condensation polymer is present in an amount of up to 100g/Kg, preferably 10 g/Kg to 80 g/Kg, more preferably 20 g/Kg to 80 g/Kg and still more preferably 20 g/Kg to 60 g/Kg.

9. The WDG of any one of the previous claims further comprising an anionic surfactant wetting agent selected from the group consisting of (a) sulfonates, (b) sulfates, (c) phosphates, (d) sulfosuccinate esters and (e) carboxylates.

10. The WDG of claim 9, wherein the anionic surfactant wetting agent is selected from the group consisting of (a) sulfonates selected from fatty alcohol ether sulfonates, fatty acid sulfonates, alkylbenzenesulfonates, alkyl naphthalene sulfonates, alkylaryl sulfonates, olefin sulfonates and alkylphenol ethoxylate sulfonates; (b) sulfates selected from alkylsulfates and alkyl ether sulfates; (c) phosphates selected from phosphates of fatty alcohol ethoxylate and phosphates of alkylphenol ethoxylate having 4 to 12 EO units; (d) sulfosuccinate esters selected from alkyl sulfosuccinates; and (e) carboxylates selected from alkylphenol ethoxylate carboxylates.

11. The WDG of claim 10 wherein the anionic surfactant wetting agent is selected from alkylbenzenesulfonates, alkylnaphthalene sulfonates, and mixtures thereof and most preferably the anionic surfactant wetting agent is a salt of alkylbenzene sulfonate, most preferably sodium dodecylbenzene sulfonate.

12. The WDG of claim 10 or claim 11, wherein the anionic surfactant wetting agent is present in an amount of at least 5 g/Kg, preferably 5 g/Kg to 80 g/Kg, more preferably 10 g/Kg to 60 g/Kg, still more preferably 15 g/Kg to 60 g/Kg and still more preferably 15 g/Kg to 40 g/Kg.

13. The WDG of any one of the previous claims, comprising finely divided filler materials include one or more selected from the group consisting of silicon dioxide, gums, insoluble metal oxides, mineral earths, bentonite, perlite, talc, kaolin, aluminium silicate, diatomaceous earth, attapulgite, barium sulfate, mica, gums such as polysaccharide gums, calcium carbonate, fused sodium potassium, precipitated silicates, aluminium silicate, zeolites and mixtures thereof.

14. The WDG of claim 13, wherein the finely divided filler comprises a phyllosilicalte, preferably selected from koalin and attapulgite.

15. The WDG of claim 13 or claim 14, wherein the filler is present in an amount of 20 g/Kg to 200 g/Kg, preferably40 g/Kg to 150 g/Kg and more preferably 80 g/Kg to 150 g/Kg.

16. The WDG composition of any one of the previous claims wherein the concentration of terbutryn is 700 g/Kg to 850 g/Kg.

17. The WDG composition of any one of the previous claims comprising: 650 g/Kg to 900 g/Kg (preferably 700 g/Kg to 850 g/Kg) terbutryn; 20 g/Kg to 100 g/Kg (preferably 20 g/Kg to 80 g/Kg) sodium polycarboxylate polymeric dispersant; 10g/Kg to 80 g/Kg (preferably 15g/Kg to 60 g/Kg) Sodium salt of sulfonated aromatic-formaldehyde condensation polymers; 5 g/Kg to 80 g/Kg (preferably 10 g/Kg to 60 g/KG) alkylbenzene sulfonate surfactant wetting agent; and 40 g/Kg to 150 g/Kg phyllosilicate filler.

18. The WDG composition of any one of the previous claims wherein the granules have a minimum dimension in the range of from 1mm to 5 mm.

19. The WDG composition of claim 18 wherein the aspect ratio (maximum/minimum dimension) of the granules is from 1 to 10, preferably 1 to 5.

20. A process for preparing a WDG according to any one of the previous claims comprising forming an finely divided mixture of the components as herein described, optionally with milling; adding water, preferably as a spray, to the finely divided mixture to form an extrudable wet mixture of the composition; extruding the wet mixture to form an extrudate; fragmenting the extrudate, preferably by cutting and/or tumbling the extrudate, to form wet granules; and optionally drying the wet granules at elevated temperature preferably at least 30°C, more preferably 30°C or 30°C to 70°C.

21. A method of pre-emergent or post emergent control of weeds comprising dispersing the WDG composition hereinbefore described in water to form an aqueous dispersion of the tebutryn herbicidal composition in water; and applying the aqueous dispersion of the tebutryn herbicidal composition in water to soil to provide pre-emergent weed control and/or to weeds to provide post- emergent weed control.

22. A method according to claim 21 wherein the weeds are controlled in a crop.

23. A method according to claim 22 wherein the crop is a pea plants (P. sativum).

24. A method of reducing phytotoxicity of terbutryn in a crop comprising formulating terbutryn as a WDG composition according to any one of claims 1 to 19, and applying an aqueous dispersion of the WDG to the crop.

25. A method according to claim 24, wherein the crop is a crop of pea plants (P. sativum).