DESC:FIELD OF THE INVENTION
[001] The present disclosure relates to compositions for control of weeds. More particularly, the present disclosure relates to synergistic herbicide combinations for control of broad spectrum of weeds and compositions of the said combinations. Method of preparation of said compositions is also provided in the disclosure.

BACKGROUND OF THE INVENTION
[002] Food security is one of the most important requirements of a country. Agriculture is an essential practice for the sustenance of human life. Various factors influence quantity and quality of yield in crops. The broad spectrum of weeds that infest fields now are a result of past malpractices. Modern science has been a great influence on the various developments in farming. Control of weeds is critical to the success of agricultural practice and farming techniques.
[003] Weed control is an important method of safeguarding the yield and quality of crops. Various weed control methods have been employed by farmers to ensure that crops are grown profitably. These methods include cultural practices, physical removal, biological methods and chemical application. Cultural practices include crop rotation and maintaining soil fertility. Physical removal of weeds by mechanical equipment proves to be labor intensive, time-consuming and causes high energy consumption. Unfortunately, it has also led to significant erosion issues on a global scale. Biological methods involve the use of natural enemies of the weed plant to control their growth and spread.
[004] The use of inorganic substances for control of weeds started more than a century ago and more recent herbicide research has provided organic herbicides, which help in achieving better yield of agricultural produce. The most dominant weeds have remained the same for decades, despite progressive changes in the use of agrochemicals. Major crops like cotton, soybean, pulses, ground nut, safflower, corn, vegetable crops, fruit crops, ornamentals, tobacco, tomato, grain or forage sorghum, peanuts, pod crops, potatoes, safflower, etc. are widely cultivated but are affected by multiple weeds that compete for sunlight, water, nutrients, and space. Weeds that affect crops include but are not limited to annual grasses, broad leaf weeds, narrow leaf weeds, sedges and others.
[005] To successfully control the growth of multiple weeds at once, it is important to increase the efficacy of herbicides by extending their spectrum. Rarely do formulations with a single active ingredient satisfy such broad-spectrum demands. As a result, compositions with one or more actives are required. Moreover, such compositions have several additional advantages such as reduction in inventory products; saving in time and money; and a reduction in the number of spray applications with herbicide.
[006] Combinations of two or more herbicides in a composition have been practiced in the art, but problems with the stability of such combinations have caused issues with respect to the application and efficacy in many cases. No single molecule or composition is known to control all the weeds and not harm the agricultural or horticultural crops. In addition, a part of known herbicide has high toxicity, and many plants develop a resistance to the chemicals over time.
[007] Therefore, there exists a need for a novel synergistic herbicide composition controlling a wide spectrum of weeds along with low toxicity and chemical stability.

SUMMARY OF THE INVENTION
[008] In one aspect, the present invention discloses a synergistic herbicide composition for weed control comprising Pyrithiobac acid or its salt thereof, a second herbicide comprising very long chain fatty acid (VLCFA) inhibitors, and agriculturally acceptable adjuvants. The said composition exhibits excellent broad spectrum control of weed species such as Acalypha indica, Commelina benghalensis, Euphorbia geniculata, Parthenium hysterophorus, Portulaca oleracea, Echinochloa colona, Eleusine indica, Bracheria sp., Corchorus capsularis, Euphorbia hirta, Physalis sp., Trianthema portulacastrum, Brachiaria eruciformis, Setaria viridis, Brachiaria reptans and Digitaria sanguinalis.
[009] In an aspect, the present invention relates to a process for preparation of synergistic herbicide composition.
[010] In another aspect, the present invention relates to a method of effective weed control in plants, said method comprising applying to the soil, a plant and/or propagation material thereof, an effective amount of the synergistic herbicide composition of the present invention.
[011] In yet another aspect, the present invention discloses a synergistic herbicide composition for weed control comprising Pyrithiobac acid or its salt thereof, a second herbicide comprising very long chain fatty acid (VLCFA) inhibitors, optionally a third active ingredient, and agriculturally acceptable adjuvants.

DESCRIPTION OF THE INVENTION
[012] The present invention is directed towards a synergistic herbicide composition for broad spectrum weed control and a method for preparation thereof.
[013] The present invention aims to provide a synergistic herbicide composition comprising Pyrithiobac or its salt and a second herbicide which shows synergistic control of broad spectrum of weeds which are not completely controlled by either Pyrithiobac or the second herbicide when used in isolation. Thereby the said composition shows synergy by controlling a broad spectrum of weeds by application of one product. The said composition exhibits excellent control over broadleaf weeds, grasses and sedges through a single application.
[014] In one aspect, the present invention provides a synergistic herbicide composition comprising of at least two types of herbicides, of which one is an early post-emergent herbicide whilst the other is a pre-emergent herbicide. Accordingly, the present invention uses at least one early post-emergent herbicide to inhibit the initial growth phase of broad leaf weeds, i.e. growth inhibition of young weed seedlings, roots and shoots. The said early post emergent herbicide is Pyrithiobac or its salt. Accordingly, the present invention uses at least one pre-emergent herbicide to prevent germinated weed seedlings from becoming established, either by inhibiting growth of root, shoot or both. The said pre-emergent herbicide is the second herbicide which is selected from the group of very long chain fatty acid (VLCFA) inhibitors.
[015] Pyrithiobac acid or its salt pyrithiobac sodium, is a post emergence herbicide useful for control of broad-leaved weeds in cotton and other crops. It belongs to the pyrimidinyl benzoate chemical family of Acetolactate synthase (ALS) inhibitors, which are placed in group 2 of classification of the Herbicide Resistance Action Committee (HRAC). Pyrithiobac acid and its salts are useful for control of broad-leaved weeds, Trianthema Spp, Amaranthus Spp, Chenopodium Spp, Digera Spp, Celosia argentea weeds. Pyrithiobac acid and its salts act by inhibiting plant amino acid synthesis by affecting the function of acetolactate synthase enzyme and eventually causing tissue death in weeds.
[016] Very long chain fatty acid (VLCFA) inhibitors act by inhibiting the biosynthesis of very long chain fatty acids in weeds. These inhibitors are placed in group 15 of classification of the Herbicide Resistance Action Committee (HRAC). VLCFA inhibitors are generally highly selective in crops. They are primarily used for residual weed control in corn, barley, oat, sorghum, soybean, wheat, sugarcane and certain vegetable crops.
[017] In an embodiment of the invention, the second herbicide comprises very long chain fatty acid (VLCFA) inhibitors which belong to the chemical family of Azolyl-carboxamides, Benzofurans, Isoxazolines, Oxiranes, Thiocarbamates, a-Oxyacetamides and a-Thioacetamides.
[018] In another embodiment of the invention, the very long chain fatty acid (VLCFA) inhibitors is selected from Cafenstrole, Fentrazamide, Ipfencarbazone, Ethofumesate, Benfuresate, Fenoxasulfone, Pyroxasulfone, Indanofan, Tridiphane, Butylate, Cycloate, Di-allate, Dimepiperate, EPTC, Esprocarb, Ethiolate, Isopolinate, Methiobencarb, Molinate, Orbencarb, Pebulate, Prosulfocarb, Sulfallate, Thiobencarb, Tiocarbazil, Tri-allate, Vernolate, Acetochlor, Alachlor, Allidochlor, Amidochlor, Butachlor, Butenachlor, CDEA, Delachlor, Diethatyl-ethyl, Dimethachlor, Dimethenamid, Dimethenamid-P, Ethachlor, Ethaprochlor, Metazachlor, Metolachlor, S-Metolachlor, Pethoxamid, Pretilachlor, Propachlor, Propisochlor, Prynachlor, Terbuchlor, Thenylchlor, Xylachlor, Anilofos, Piperophos, and salts thereof.
[019] Metolachlor belongs to the a-Chloroacetamide chemical family of very long chain fatty acid (VLCFA) inhibitors. It is a selective pre-emergence herbicide for the control of annual grass weeds, yellow nutsedge and some broadleaf species. Metolachlor exists as the S- and R- enantiomers. The S-enantiomer is found to be considerably more active than the R-enantiomer. S-Metolachlor is a mixture of S- and R-formats in an approximate ratio 88:12.
[020] Pyroxasulfone is a pre-emergence herbicide for control of grasses and small-seeded broad leaf weeds. It belongs to the Isoxazoline chemical family of very long chain fatty acid (VLCFA) inhibitors.
[021] In an embodiment of the invention, the pre-emergent herbicide or the second herbicide is selected from Metolachlor, S-Metolachlor, Pyroxasulfone, Fentrazamide, Ipfencarbazone, Ethofumesate, Benfuresate, Molinate, Orbencarb, Pebulate, Prosulfocarb, Thiobencarb, Acetochlor, Butachlor, Dimethachlor, Metazachlor, Pethoxamid, Pretilachlor, Propisochlor, Anilofos, Piperophos, and any salt thereof.
[022] In another embodiment of the invention, the synergistic herbicide composition comprises an effective amount of the Pyrithiobac acid or its salt thereof (1-99 wt.%), the second herbicide (1-99 wt.%), and the agriculturally acceptable adjuvants. The wt.% is based on the total weight of the composition.
[023] In yet another embodiment of the invention, the synergistic herbicide composition comprises an effective amount of the Pyrithiobac acid or its salt thereof (1-99 wt.%), the second herbicide (1-99 wt.%), optionally a third active ingredient (1-99 wt.%), and the agriculturally acceptable adjuvants.
[024] In an embodiment of the invention, the weight ratio of the Pyrithiobac acid or its salt to the second herbicide is in the range of 1:25 to 25:1. In a preferred embodiment, Metolachlor is the second herbicide. In another preferred embodiment, S-Metolachlor is the second herbicide. In yet another embodiment, Pyroxasulfone is the second herbicide.
[025] In an embodiment of the invention, the third active ingredient is selected from a group comprising of amino acids, plant growth regulators, bio-stimulants, micronutrients, phytotonic chemicals, and phytostimulants.
[026] In another embodiment of the invention, the third active ingredient is selected from the group comprising Glycine, Proline, Hydroxyproline, Glutamic acid, Glutamate, Alanine, Arginine, Cysteine, Phenylalanine, Tryptophan, and a mixture of amino acids, Auxins, Cytokinins, Gibberellins, Abscisic acid, Ethylene, Dormins, Abscissic Acid (ABA), Phaseic Acid, Florigin, Anthesin, Vernalin, Phenolic Substances, Coumarin, Vitamins, Phytochrome Substances, Synthetic Auxins, Synthetic Cytokinins, Fulvic acid, Humic Acid, Chitosan, Homobrassinolide, Triacontanol, Biochemical Materials, Seaweed Extracts, Micronutrients like Boron (B), Chloride (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Nickel (Ni) and Zinc (Zn), and Phytotonic chemicals.
[027] In yet another embodiment of the invention, the third active ingredient is selected from Fulvic acid, Humic acid, Homobrassinolide, Triacontanol, and mixtures thereof.
[028] The agrochemically adjuvants are selected from the group comprising of emulsifier, adjuvant, co-solvent, surfactant, aromatic hydrocarbon, polymer, dyes, sand, suspension aids, carriers, solvents, stabilizers, anti-foaming agents, anti-freezing agents, wetting agent, preservatives, antioxidants, colorants, thickeners, solid adherents, inert fillers, dispersing agents, diluents, chelating agents, surfactants, clays, and mixtures thereof. The agriculturally acceptable adjuvants in a pre-determined ratio aid improving physical stability and prevent the degradation of the composition leading to long term stability and wide spectrum activity. The employment of adjuvants used in the composition will depend upon the type of formulation and/or the way the formulation is to be applied by the end user.
[029] The synergistic herbicide composition described hereinabove can be formulated in a dosage form selected from Emulsifiable Concentrate (EC), Microemulsion (ME), Aqueous Emulsion Concentrate (EW), Granules (GR), Suspension Concentrate (SC), Water Dispersible Granules (WG), Wettable Powder (WP), Soluble Granule (SG), Soluble Concentrate (SL), ZC - a mixed formulation of capsule suspension (CS) and suspension concentrate (SC), Capsule Suspension (CS), Suspoemulsion (SE), Oil Dispersion(OD), Flowable suspension (FS), Emulsion for seed treatment (ES), Water dispersible powder for slurry treatment (WS), and Powder for dry seed treatment (DS).
[030] In a preferred embodiment of the invention, the synergistic herbicide composition is formulated in the Suspoemulsion (SE) dosage form. In another embodiment, the synergistic herbicide composition is formulated in the Emulsifiable Concentrate (EC) dosage form or the Aqueous Emulsion Concentrate (EW) dosage form.
[031] In an embodiment, the agriculturally acceptable adjuvants may comprise of one or more emulsifiers, suspending agent, wetting agent, defoamer, biocide, one or more rheology modifiers, humectant, anti-freeze agent and vehicle.
[032] In a preferred embodiment, the agriculturally acceptable adjuvants comprise of high molecular weight (>10000 Daltons) polymeric emulsifier, calcium alkylaryl sulphonate, polyalkylene oxide block copolymer, sodium lignosulfonate, aluminum oxide, silicon antifoam emulsion, 1,2-benzisothiazolin-3-one, xanthan gum, propylene glycol, and water.
[033] In another embodiment, the agriculturally acceptable adjuvants comprise of calcium dodecyl benzene sulfonic acid, tristyrylphenol ethoxylate, methanol, and aromatic hydrocarbon solvent.
[034] In yet another embodiment, the agriculturally acceptable adjuvants comprise of alkoxylated phosphate ester, blend of calcium sulfonate and nonionic surfactant, acrylate comb polymer, sodium lignosulfonate, polydimethylsiloxane, xanthan gum, 1,2 - Benzisothiazoline - 3 – one, propylene glycol, and water.
[035] In another embodiment, the agriculturally acceptable adjuvants comprise of high molecular weight (>10000 Daltons) nonionic polymer, blend of calcium sulfonate and nonionic surfactant, acrylate comb polymer, sodium lignosulfonate, polydimethylsiloxane, xanthan gum, 1,2 - Benzisothiazoline - 3 – one, propylene glycol, and water.
[036] Another aspect of the invention provides a method for preparation of the synergistic herbicide composition, as described above. Accordingly, the embodiments pertaining to the composition are applicable here as well.
[037] A person skilled in the art is well aware of suitable techniques for preparing various dosage forms, as described herein. The accompanying passages describe exemplary embodiments for preparing the various dosage forms.
[038] In an embodiment of the present invention, the synergistic herbicide composition is formulated in a suspension concentrate (SC) dosage form or an oil dispersion (OD) dosage form. Accordingly, the method for preparation of the composition comprises: a) preparing a liquid pre-mix comprising a liquid phase and requisite ingredients such as suspending agent, wetting agent, spreader, surfactant, dispersing agent, preservative, and defoamer, with uniform mixing; b) obtaining a slurry comprising the liquid pre-mix from step a) and the active ingredients; c) mixing the thickener and/or stabilizer to the slurry of step b) to obtain the suspension concentrate (SC) dosage form or the oil dispersion (OD) dosage form.
[039] In another embodiment of the present invention, the synergistic composition is formulated in the emulsion concentrate (EC) dosage form, or the aqueous emulsion concentrate (EW) dosage form, or the microemulsion (ME) dosage form. Accordingly, the method for preparation of the composition comprises: a) mixing water, humectant, one or more emulsifiers, surfactant, and defoamer in a vessel with stirring to obtain an aqueous phase; b) preparing a non-aqueous/oily phase comprising the active ingredients, c) emulsifying the aqueous and non-aqueous phase using high speed mixing equipment, followed by addition of adjuvants such as stabilizers, biocide, and rheology modifiers with requisite mixing, to obtain the emulsion concentrate (EC) dosage form.
[040] In yet another embodiment of the present invention, the synergistic composition is formulated in the water dispersible granules (WG) dosage form, or the wettable powder (WP) dosage form, or the soluble granule (SG) dosage form. Accordingly, the method for preparation of the composition comprises: a) preparing a homogenous mix by charging the requisite quantities of the active ingredients, binder, and surfactants in a blender and mixing till complete homogenization is achieved; b) milling the homogenous mix to a desirable size (e.g., 0.8 mm to 1.5 mm), followed by blending again for homogeneity; c) passing the homogenous mixture from step b) through an extruder for granulation; d) drying the granules through a fluid bed dryer to remove excess moisture; and e) passing the granules obtained after step d) through a vibro sifter to obtain the granule dosage form.
[041] In a further embodiment of the present invention, the synergistic herbicide composition is formulated in the suspoemulsion (SE) dosage form. Accordingly, the method for preparation of the composition comprises mixing the EW dosage form with the SC dosage form to obtain the SE dosage form.
[042] In yet another embodiment of the present invention, the synergistic herbicide composition is intended to be used as a standalone formulation and/or in various dosage forms, described hereinabove and use by tank mix method or via sequential application.
[043] The method of preparing the present formulation can be modified suitably by the person skilled in the art based on the knowledge of manufacturing the formulation. However, all such variations and modifications should be considered to be within the scope of present invention.
[044] In a preferred embodiment of the present invention, the synergistic composition comprises of herbicidally effective amounts of the Pyrithiobac Acid or its salt thereof, Metolachlor, and the agriculturally acceptable adjuvants.
[045] In an embodiment of the present invention, the synergistic composition comprises of herbicidally effective amounts of the Pyrithiobac Acid or its salt thereof, Metolachlor, the third active ingredient, and the agriculturally acceptable adjuvants.
[046] In another embodiment of the present invention, the synergistic composition comprises of herbicidally effective amounts of the Pyrithiobac Acid or its salt thereof, S-Metolachlor, and the agriculturally acceptable adjuvants.
[047] In yet another embodiment of the present invention, the synergistic composition comprises of herbicidally effective amounts of the Pyrithiobac Acid or its salt thereof, S-Metolachlor, the third active ingredient, and the agriculturally acceptable adjuvants.
[048] In a further embodiment of the present invention, the synergistic composition comprises of herbicidally effective amount of the Pyrithiobac Acid or its salt thereof, Pyroxasulfone, and the agriculturally acceptable adjuvants.
[049] In still another embodiment of the present invention, the synergistic composition comprises of herbicidally effective amounts of the Pyrithiobac Acid or its salt thereof, Pyroxasulfone, the third active ingredient, and the agriculturally acceptable adjuvants.
[050] In an embodiment of the present invention, the synergistic composition has been designed to be used against broad spectrum control of weed flora for variety of crops.
[051] In another embodiment of the invention, the synergistic composition has been designed to be used against broad spectrum control of weed flora in cotton, ground nut and soybean.
[052] Accordingly, the synergistic herbicide composition is used to control weed species such as Acalypha indica, Commelina benghalensis, Euphorbia geniculata, Parthenium hysterophorus, Portulaca oleracea, Echinochloa colona, Eleusine indica, Bracheria sp., Corchorus capsularis, Euphorbia hirta, Physalis sp., Trianthema portulacastrum, Brachiaria eruciformis, Setaria viridis, Brachiaria reptans and Digitaria sanguinalis.
[053] In an embodiment, the composition can be applied to the locus of the plant, including all plant parts, or on the soil or turf of growth. Further, the composition can be applied before or after the crop seeds are planted.

EXAMPLES
[054] The following examples are illustrative of the present invention but not limitative of the scope thereof:
[055] Example 1) – a. Pyrithiobac acid 2.5% + Metolachlor 40% SE, b. Pyrithiobac acid 2.5% + S-Metolachlor 38.4% SE and c. Pyrithiobac acid 2.5% + Metolachlor 40% + Humic acid 1% SE
Component Name a.
% w/v b.
% w/v c. % w/v
Pyrithiobac acid 68.5% 3.72 3.72 3.72
Metolachlor @98.5% 41.11 0 41.11
S-Metolachlor @98% 0 39.80 0
Potassium humate (Humic acid 70%) 0 0 1.5
High molecular weight (>10000 Daltons) polymer 2.67 2.67 2.67
Polyalkylene oxide block copolymer 2.23 2.23 2.23
Calcium arylalkyl sulphonate 0.89 0.89 0.89
Sodium lignosulfonate 0.41 0.41 0.41
Polydimethylsiloxane 0.2 0.2 0.2
Xanthan Gum (2%) 7.83 7.83 7.83
Aluminum oxide 0.08 0.08 0.08
1,2-propanediol 4.86 4.86 4.86
1,2 - Benzisothiazoline - 3 – one 0.05 0.05 0.05
Water q.s to 100 q.s to 100 q.s to 100
[056] The method for preparation of a. Pyrithiobac acid 2.5% + Metolachlor 40% SE, b. Pyrithiobac acid 2.5% + S-Metolachlor 38.4% SE and c. Pyrithiobac acid 2.5% + Metolachlor 40% + Humic acid 1% SE compositions from Example 1 comprise the following steps – a) Preparation of d. Metolachlor 45% EW phase / e. S-Metolachlor 45% EW phase / f. Metolachlor 45% + Humic acid 1% EW phase
Component Name d.
% w/v e.
% w/v f.
% w/v
Metolachlor @98.5% 47.71 0 47.71
S-Metolachlor @98% 0 46.43 0
Potassium Humate (Humic acid 70%) 0 0 1.75
High molecular weight (>10000 daltons) polymer 3 3 3
Polyalkylene oxide block copolymer 2.5 2.5 2.5
Calcium arylalkyl sulphonate 1 1 1
Polydimethylsiloxane 0.2 0.2 0.2
Xanthan Gum (2%) 5 5 5
1,2-propanediol 5 5 5
1,2 - Benzisothiazoline - 3 – one 0.05 0.05 0.05
Water q.s to 100 q.s to 100 q.s to 100

Water was charged into a vessel with overhead stirrer and ultra shear mixer. 1,2-propanediol and potassium humate (only for f. Metolachlor 45% + Humic acid 1% EW phase) was added to the said vessel with stirring at 100 rpm for 5 minutes. Requisite quantities of surfactants (High molecular weight (>10000 daltons), Polyalkylene oxide block copolymer, Calcium arylalkyl sulphonate), polydimethylsiloxane and 1,2 - Benzisothiazoline - 3 – one was added to the said vessel with stirring for 15 minutes. Required quantities of Metolachlor/ S-Metolachlor was added and mixed via ultra shear homogenizer at 5000 rpm for 1 hour. The contents of the vessel were transferred into a new vessel with ordinary stirrer. To this new vessel, xanthan gum was added with stirring at 100 rpm for 2 hours to obtain final EW phase.
b) Preparation of Pyrithiobac acid 30% SC phase:
Component Name % w/v
Pyrithiobac acid 68.5% 45.25
Sodium lignosulfonate 5
Polydimethylsiloxane 0.25
Xanthan Gum (2%) 7.5
Aluminum oxide 1
1,2-propanediol 5
1,2 - Benzisothiazoline - 3 – one 0.1
Water q.s to 100

Requisite quantity of water was charged in a vessel with anchor stirrer. 1,2-propanediol was added, followed by sodium lignosulfonate in required amounts with continuous stirring. 1,2 - Benzisothiazoline - 3 – one, polydimethylsiloxane and aluminium oxide were added with stirring. Pre-weighed amount of Pyrithiobac acid was added slowly with continuous stirring to the vessel. The contents of the vessel were then passed through the bead mill to obtain desired particle size. Xanthan gum was added to the mixture with desired particle size (where D90 is lesser than 20 microns) with continuous stirring to obtain final SC phase.
c) Mixing of EW phase with SC phase to obtain final SE composition –
Component Name a. % w/v b. % w/v c. % w/v
Metolachlor 45% EW phase 86.17 0 0
S-Metolachlor 45% EW phase 0 85.71 0
Metolachlor 45% + Humic acid 1% EW 0 0 86.17
Pyrithiobac acid 30% SC 8.23 8.23 8.23
Xanthan Gum (2%) (Rhodopol 23) 2.5 2.5 2.5
Water q.s to 100 q.s to 100 q.s to 100
Requisite quantity of water, Metolachlor 45% SE / S-Metolachlor 45% EW / Metolachlor 45% + Humic acid 1% EW was charged into a vessel fitted with anchor stirrer. Required amount of Pyrithiobac 30% SC was added with stirring for 15 minutes, followed by addition of Xanthan gum with continuous mixing for 30 minutes to obtain final SE composition.
[057] Example 2 – a. Pyrithiobac acid 30 %+ Metolachlor 3% SE and b. Pyrithiobac acid 30 %+ S-Metolachlor 2.5 % SE
Component Name a.
% w/w b.
% w/w
Pyrithiobac acid 68.5% 43.71 43.71
Metolachlor @98.5% 3.04 0
S-Metolachlor @98% 0 2.55
High molecular weight (>10000 daltons) polymer 0.16 0.13
Polyalkylene oxide block copolymer 0.13 4.29
Calcium arylalkyl sulphonate 0.05 0.04
Sodium lignosulfonate 4.29 0.11
Polydimethylsiloxane 0.22 0.2
Xanthan Gum (2%) 11.56 11.54
Aluminum oxide 0.86 0.86
1,2-propanediol 4.55 4.50
1,2 - Benzisothiazoline - 3 – one 0.09 0.09
Water q.s to 100 q.s to 100

[058] The process for preparation of a. Pyrithiobac acid 30 %+ Metolachlor 3% SE and b. Pyrithiobac acid 30 %+ S-Metolachlor 2.5 % SE compositions from Example 2 comprise of the following steps –
a. Preparation of c. Metolachlor 57.5% EW phase / d. S-Metolachlor 57.5% EW phase
Component Name c.
% w/v d.
% w/v
Metolachlor @98.5% 58.37 0
S-Metolachlor @98.5% 0 58.37
High molecular weight (>10000 daltons) polymer 3 3
Polyalkylene oxide block copolymer 2.5 2.5
Calcium arylalkyl sulphonate 1 1
Polydimethylsiloxane 0.2 0.2
Xanthan Gum (2%) 2.5 2.5
1,2-propanediol 5 5
1,2 - Benzisothiazoline - 3 – one 0.05 0.05
Water q.s to 100 q.s to 100
Water was charged into a vessel with overhead stirrer and ultra shear mixer. 1,2-propanediol was added to the said vessel with stirring at 100 rpm for 5 minutes. Requisite quantities of surfactants (High molecular weight (>10000 daltons) polymer, Polyalkylene oxide block copolymer, Calcium arylalkyl sulphonate), polydimethylsiloxane and 1,2 - Benzisothiazoline - 3 – one was added to the said vessel with stirring for 15 minutes. Pre-weighed quantities of Metolachlor/ S-Metolachlor was added and mixed via ultra shear homogenizer at 5000 rpm for 1 hour. The contents of the vessel were transferred into a new vessel with ordinary stirrer. To this new vessel, xanthan gum was added with stirring at 100 rpm for 2 hours to obtain final EW phase.
b) Preparation of Pyrithiobac acid 35% SC phase
Component Name % w/v
Pyrithiobac acid 68.5% 51
Sodium lignosulfonate 5
Polydimethylsiloxane 0.25
Xanthan Gum (2%) 7.5
Aluminum oxide 1
1,2-propanediol 5
1,2 - Benzisothiazoline - 3 – one 0.1
Water q.s to 100
Requisite quantity of water was charged in a vessel with anchor stirrer. 1,2-propanediol was added, followed by sodium lignosulfonate in required amounts with continuous stirring. 1,2 - Benzisothiazoline - 3 – one, aluminum oxide and polydimethylsiloxane were added with stirring. Pre-weighed amount of Pyrithiobac acid was added slowly with continuous stirring to the vessel. The contents of the vessel were then passed through the bead mill to obtain desired particle size. Xanthan gum was added to the mixture with desired particle size (where d90 is lesser than 20 microns) with continuous stirring to obtain final SC phase.
c) Mixing of EW phase with SC phase to obtain final SE composition –
Component Name a. % w/v b. % w/v
Metolachlor 57.5% EW phase 5.21 0
S-Metolachlor 57.5% EW phase 0 4.35
Pyrithiobac acid 35% SC 85.71 85.71
Xanthan Gum (2%) (Rhodopol 23) 5 5
Water q.s to 100 q.s to 100
Requisite quantity of water, Metolachlor 57.5% EW / S-Metolachlor 57.5% EW was charged into a vessel fitted with anchor stirrer. Required amount of Pyrithiobac 35% SC was added with stirring for 15 minutes, followed by addition of Xanthan gum with continuous mixing for 30 minutes to obtain final SE composition.
[059] Example 3 – a. Pyrithiobac Acid 2.5 %+ Metolachlor 62.5 % EC, b. Pyrithiobac Acid 2.5% + S-Metolachlor 60.0% EC, c. Pyrithiobac Acid 1.5%+ Metolachlor 60% EC, and d. Pyrithiobac Acid 1.5% + S-Metolachlor 63% EC
Component Name a. % w/w b. % w/w c. % w/w d. % w/w
Pyrithiobac acid 92.5% 2.7 2.7 1.62 1.62
Metolachlor 98.5% 63.45 0 61 0
S-Metolachlor 98% 0 61.22 0 64.3
Calcium dodecyl benzene sulfonic acid
6 6.5 6 6.5
Tristyrylphenol ethoxylate 4 3.5 4 3.5
Methanol 10 10 10 10
Aromatic hydrocarbon q.s to 100 q.s to 100 q.s to 100 q.s to 100

[060] As will be noted above, formulations c. and d. above are comparative formulations prepared with a ratio between Pyrithiobac acid and S-Metolachlor of 40:1 and 42:1, respectively. These formulations incorporate active ingredient doses exceeding the maximum permissible limits set by regulatory authorities. In contrast, the ratio of Pyrithiobac acid and S-Metolachlor in the present invention, ranging from 1:25 to 25:1, remains within the regulatory limits for the maximum allowable dose of each active ingredient, thereby allowing for bio-efficacy studies to be conducted without requiring the need for additional toxicology studies.
[061] The process for preparation of a. Pyrithiobac Acid 2.5 %+ Metolachlor 62.5 % EC, b. Pyrithiobac Acid 2.5% + S-Metolachlor 60.0% EC, c. Pyrithiobac Acid 1.5%+ Metolachlor 60% EC and d. Pyrithiobac Acid 1.5% + S-Metolachlor 63% EC from Example 3 comprise of the following steps – a) Requisite quantities of methanol was charged in a vessel fitted with stirrer. b) Pre-weighed amount of Pyrithiobac acid was added slowly to the vessel with continuous stirring at 500 rpm for 15 minutes. c) Requisite quantities of aromatic hydrocarbon solvent were charged to the vessel with stirring. d) Pre-weighed amount of Metolachlor / S-Metolachlor was added to the vessel with continuous stirring. e) Pre-determined quantities of emulsifier (Calcium dodecyl benzene sulfonic acid and Tristyrylphenol ethoxylate) were added to the vessel with continuous stirring for 2 hours to obtain the final EC composition.
[062] Example 4 – a. Pyrithiobac sodium 2.5% + Metolachlor 40% EW and b. Pyrithiobac sodium 2.5 % + S-Metolachlor 38.4 % EW
Component Name a.
% w/w b.
% w/w
Pyrithiobac sodium 2.5 2.5
Metolachlor @98.5% 41.11 0
S-Metolachlor @98% 0 38.4
Alkoxylated phosphate ester 3 0
High molecular weight (>10000 daltons) polymer 0 2.5
Blend of calcium sulfonate and nonionic
surfactant 3 1
Acrylate comb polymer 2.5 2.5
Sodium lignosulfonate 1 0.5
Polydimethylsiloxane 0.2 0.2
Xanthan Gum (2%) 7 8.5
1,2-propanediol 7 7
1,2 - Benzisothiazoline - 3 – one 0.1 0.1
Water q.s to 100 q.s to 100

[063] The process for preparation of a. Pyrithiobac sodium 2.5% + Metolachlor 40% EW and b. Pyrithiobac sodium 2.5 % + S-Metolachlor 38.4 % EW from Example 4 comprise of the following steps – a) Requisite quantities of water was charged into a vessel fitted with overhead stirrer and ultra shear mixer. b) 1,2-propanediol was added to the vessel with stirring for 15 minutes at 100 rpm speed. c) Requisite quantity of Pyrithiobac sodium was added to the vessel with stirring. d) Pre-weighed quantities of sodium lignosulfonate, surfactants (Alkoxylated phosphate ester, High molecular weight (>10000 daltons) polymer, Blend of calcium sulfonate and nonionic surfactant, Acrylate comb polymer), polydimethylsiloxane and 1,2 - Benzisothiazoline - 3 – one was added to the vessel under continuous stirring for 15-20 minutes. e) Required quantity of Metolachlor / S-Metolachlor was charged to the vehicle with stirring via ultra shear mixer at 5000 rpm for 1 hour duration. f) The contents of the vessel were transferred to a new vessel with an ordinary stirrer. g) Xanthan gum (pre-weighed) was added to the new vessel with stirring at 100 rpm for 2-6 hours.
[064] The inventive compositions of the examples 1-4 were found to be stable during accelerated stability studies at 54?C for 14 days.
[065] Bio-efficacy studies
[066] The studies were carried out in farm fields on cotton crops grown under natural outdoor conditions. on plots under natural outdoor conditions. The treatment combinations included herbicidal SE composition of the invention at a certain dose, recommended dose of Pyrithiobac sodium, Metolachlor respectively, along with one treatment of untreated control. The said compositions were applied as spray on the cotton field within 0-3 days of sowing at an application rate of 500-liter water per hectare using knapsack sprayer with flat fan nozzle. The number of individual weed species present in the field was recorded from three random 1 sq.m spots per plot at 21 and 28 days after application. Weed wise percent weed control is calculated using the formula:
% Weed control = ((C-T)/C) x 100
C = mean weed density per sqm in untreated plot
T = mean weed density per sqm in treated plot
[067] Further, Colby's equation was used to determine the herbicidal effects expected from the mixtures. (See Colby, S. R. Calculation of the synergistic and antagonistic response of herbicide combinations. Weeds 1967, 15, 20 - 22.) The following equation was used to calculate the expected activity of mixtures containing two active ingredients, A and B:
Expected = A + B - (A x B/100)
A = Observed efficacy of active component A at the same concentration as used in the mixture; B = Observed efficacy of active component B at the same concentration as used in the mixture.
[068] A response is synergistic when an observed value is greater than the calculated value. A synergistic response is understood to be one in which the interaction response is greater than the sum of the responses from the individual herbicidal treatments. An antagonistic response is the opposite situation. The ability of the compositions described herein to afford suitable weed control is illustrated by the efficacy data in Tables 1 and 2:
[069] Table 1. Broad leaf weed control exhibited by Pyrithiobac acid 2.5% + Metolachlor 40% SE of the present invention
Treatment Dose
g a.i./Ha % Weed control after 28 DAA
Acalypha indica Commelina benghalensis Parthenium hysterophorus Portulaca oleracea
Pyrithiobac sodium 10% EC 62.50 58.97 89.47 50 77.59
Metolachlor 50% EC 1000 64.10 42.11 33.33 40.63
Expected response as per Colby Formula - 85.28 93.91 66.66 86.7
Pyrithiobac acid 2.5 + Metolachlor 40% SE 1062.50 94.87 100 91.67 93.95
[070] Table 2. Grasses weed control exhibited by Pyrithiobac acid 2.5% + Metolachlor 40% SE of the present invention

Treatment Dose
g a.i./Ha % Weed control after 21 DAA
Digitaria sanguinalis Echinochloa colona Eleusine indica Brachiaria reptans
Pyrithiobac sodium 10% EC 62.50 71.43 56.59 50.86 53.48
Metolachlor 50% EC 1000 77.14 71.43 86.21 73.22
Expected response as per Colby Formula - 93.47 87.6 93.23 87.55
Pyrithiobac acid 2.5% + Metolachlor 40% SE 1062.50 100 100 100 94.33

[071] It can be observed from Table 1 and 2 that Pyrithiobac acid 2.5% + Metolachlor 40% SE of the present invention shows synergy when compared to individual Pyrithiobac and Metolachlor application for the following weeds Acalypha indica, Commelina benghalensis, Parthenium hysterophorus, Portulaca oleracea, Digitaria sanguinalis, Echinochloa colona, Eleusine indica and Brachiaria reptans.
[072] Table 3 shows the population of weeds influenced by the synergistic herbicide composition of the present invention in comparison with individual active applications and untreated control, 21 days after application in cotton.
[073] Table 3 - % Total weed control
Treatment Doseg a.i./ Ha Density of weeds (No/Sq.m) Total weed density per sq. m % Total weed control
Acalypha indica Setaria viridis Brachiaria reptans Echinochloa colona Portulaca oleraceae
Pyrithiobac acid 2.5% + Metolachlor 40% SE 1062.5 0.44 2.67 5.33 21.33 6.22 35.99 85.57
Pyrithiobac sodium 10% EC 62.5 4.89 12.44 8.89 35.11 14.22 75.55 67.3
Metolachlor 50% EC 1000 5.78 4.89 7.11 42.67 42.67 103.12 55.38
Untreated control - 23.56 18.22 31.11 80.89 77.33 231.11 0
[074] It can be observed from Table 3 that Pyrithiobac acid 2.5% + Metolachlor 40% SE composition of the present invention shows better % total weed control than individual application of Pyrithiobac and Metolachlor at comparable dose rates.
[075] The study results in the above tables 1-3 show that the compositions of the present invention are very effective in controlling total weed flora broad leaf weeds like Acalypha indica, Commelina benghalensis, Parthenium hysterophorus, Portulaca oleracea and grasses like Digitaria sanguinalis, Echinochloa colona, Eleusine indica, Brachiaria reptans, Setaria viridis and Brachiaria reptans in cotton as compared to Pyrithiobac and Metolachlor individually. It also clearly shows the synergistic effect of the composition of the present invention with longer herbicidal effect up to 28-36 days, when compared to individual herbicide application.
[076] The herbicides applied in combination as per the present invention generally increased the spectrum of weed control and the length of residual weed control in a single application that saves time and labor in a weed management program.
[077] High percentage weed control was recorded with the application of the compositions of the invention when compared with individual application of each active ingredient.
[078] Advantageously, the present invention provides a synergistic composition that exhibits extremely useful weed controlling activity and has no impact on non-target beings such as friendly insects, fishes, mammals etc.
Phytotoxicity and Crop Compatibility Studies
[079] After spraying the SE composition of the present invention and individual applications of Pyrithiobac and Metolachlor individually on cotton crops as explained above, the cotton crop was continuously monitored and evaluated for phytotoxicity symptoms and crop health on a scale of 0-10 as shown in the following Table 4 - Scale
Effect Rate Crop description and condition
None 0 No injury, normal
Slight 1 Slight stunting, injury discoloration
2 Some stand loss, stunting or discoloration
3 Injury more pronounced but not persistent
Moderate 4 Moderate injury, recovery possible
5 Injury more persistent, recovery doubtful
6 Near severe injury, stand loss surviving
Severe 7 Severe injury, stand loss surviving
8 Almost destroyed, a few plants surviving
9 Very few plants alive
Complete 10 Complete destruction
[080] Table 5 shows mean observations recorded after 1, 3, 5, 10, 15 and 30 days after application
Treatment Phytotoxicity
Yellowing Necrosis Epinasty/
Hyponasty Vein Clearing Scorching Wilting
Pyrithiobac acid 2.5% + Metolachlor 40% SE 0 0 0 0 0 0
Untreated control 0 0 0 0 0 0

[081] Table 5 shows that there is zero effect of herbicides on the crop plants either as SE composition or individually thereby indicating that the SE composition of the invention is safe to cotton crops. As seen in the above table, all values are zero denoting that no phytotoxic effects have been noted for all treatments including control on cotton crop plants.
[082] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since the modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to the person skilled in the art, the invention should be construed to include everything within the scope of the disclosure.
,CLAIMS:We Claim:
1. A synergistic herbicide composition for weed control comprising Pyrithiobac acid or its salt thereof, a second herbicide comprising very long chain fatty acid (VLCFA) inhibitors, and agriculturally acceptable adjuvants.
2. The synergistic herbicide composition as claimed in claim 1, wherein the weight ratio between the Pyrithiobac acid or its salt thereof and the second herbicide ranges between 1:25 to 25:1.
3. The synergistic herbicide composition as claimed in claim 1, wherein the very long chain fatty acid (VLCFA) inhibitors are selected from Cafenstrole, Fentrazamide, Ipfencarbazone, Ethofumesate, Benfuresate, Fenoxasulfone, Pyroxasulfone, Indanofan, Tridiphane, Butylate, Cycloate, Di-allate, Dimepiperate, EPTC, Esprocarb, Ethiolate, Isopolinate, Methiobencarb, Molinate, Orbencarb, Pebulate, Prosulfocarb, Sulfallate, Thiobencarb, Tiocarbazil, Tri-allate, Vernolate, Acetochlor, Alachlor, Allidochlor, Amidochlor, Butachlor, Butenachlor, CDEA, Delachlor, Diethatyl-ethyl, Dimethachlor, Dimethenamid, Dimethenamid-P, Ethachlor, Ethaprochlor, Metazachlor, Metolachlor, S-Metolachlor, Pethoxamid, Pretilachlor, Propachlor, Propisochlor, Prynachlor, Terbuchlor, Thenylchlor, Xylachlor, Anilofos, Piperophos, and salts thereof.
4. The synergistic herbicide composition as claimed in claim 1, wherein the second herbicide is Metolachlor.
5. The synergistic herbicide composition as claimed in claim 1, wherein the second herbicide is S-Metolachlor.
6. The synergistic herbicide composition as claimed in claim 1, wherein the second herbicide is Pyroxasulfone.
7. The synergistic herbicide composition as claimed in claim 1, wherein the agriculturally acceptable adjuvants are selected from carrier, defoamer, wetting agent, disintegrating agent, anti-caking agent, dispersing agent, emulsifier, aromatic hydrocarbon, colorant, polymeric film forming agent, solid adherent, sticking agent, surfactant, co-solvent, polymeric surfactant, dyes, colorant, sand, oil, stabilizer, preservative, antioxidant, thickener, viscosity modifying agent, rheology modifying agent, anti-foaming agent, anti-freezing agent, inert filler, diluent, chelating agent, clays, and mixtures thereof.
8. The synergistic herbicide composition as claimed in claim 1 further comprising a third active ingredient selected from amino acids, plant growth regulators, bio-stimulants, micronutrients, phytotonic chemicals, and phytostimulants.
9. The synergistic herbicide composition as claimed in claim 1, wherein said composition is formulated in a dosage form selected from Emulsifiable Concentrate (EC), Aqueous Emulsion Concentrate (EW), Granules (GR), suspension concentrate (SC) formulation, Water Dispersible Granules (WG), Wettable Powder (WP), ZC a mixed formulation of capsule suspension (CS) and suspension concentrate (SC), Suspoemulsion (SE), Oil Dispersion(OD), Flowable suspension (FS), water dispersible powder for slurry treatment (WS), and powder for dry seed treatment (DS).
10. The synergistic herbicide composition as claimed in claim 1, wherein said composition is formulated in a Suspoemulsion (SE) dosage form.
11. The synergistic herbicide composition as claimed in claim 1, wherein said composition is formulated in an Emulsifiable Concentrate (EC) dosage form.
12. The synergistic herbicide composition as claimed in claim 1, wherein said composition is formulated in an Aqueous Emulsion Concentrate (EW) dosage form.
13. The synergistic herbicide composition as claimed in claim 1, wherein said composition affords control of weeds selected from a group consisting of Commelina benghalensis, Acalypha Indica, Parthenium hysterophorus, Portulaca oleracea, Eleusina indica, Corchorus capsularis, Euphorbia hirta, Trianthema portulacastrum, Bracheria sp., Brachiaria eruciformis, Echinochloa colona, Euphorbia geniculata, Digitaria sanguinalis, Setaria viridis, Brachiaria reptans, Physalis sp., or combination thereof.
14. A method of effective weed control in plants, said method comprising applying to the soil, a plant and/or propagation material thereof, an effective amount of the synergistic herbicide composition as claimed in claims 1 to 13.
15. Use of the synergistic herbicide composition claimed in claims 1 to 13 for weed control in soil, a plant and/or propagation material thereof.
Dated this 9th day of February 2024.
Godrej Agrovet Limited
By their Agent & Attorney

(Nisha Austine)
of Khaitan & Co
Reg. No. IN/PA-1390