DESC:FIELD OF THE INVENTION
[001] The invention relates to herbicidal compositions, more particularly to a broad spectrum synergistic herbicidal formulation and a preparation method thereof.

BACKGROUND OF THE INVENTION
[002] Food security is one of the most essentials requirements of a country and modern science has been a great influence on the various developments in farming. There are many factors that influence quantity and quality of yield, but ultimately agriculture is an essential practice without which human life is not possible. The huge increase of weeds that infest fields are a result of past malpractices. At present, they are conclusively connected to the development of crops and farming techniques.
[003] Tillage is one tool for weed management that is particularly effective. However, mechanical weed control is time-consuming, labor-intensive, and uses a lot of energy. Unfortunately, it has also led to significant erosion issues on a global scale. The use of inorganic substances started more than a century ago and at present chemical weed control has evolved into the era of organic herbicides. Herbicide research with a specific purpose has produced a continual supply of profitable goods. Despite major changes in the use of agrochemicals, the most dominant weeds have remained the same for decades. Wheat is one such crop which is widely cultivated but is affected by multiple weeds that compete with wheat for sunlight, water, nutrients, and space. In addition, they harbor insects and pathogens, which attack crops.
[004] To successfully control the growth of multiple weeds at once, the efficacy of herbicides must be increased by extending their spectrum. Rarely formulations with a single active ingredient satisfy such broad-spectrum demands. As a result, two or more active compositions are needed. Moreover, such compositions comprising two or more actives have several additional advantages such as reduction in inventory products; saving in time and money; and a reduction in the number of times the crop is sprayed with the herbicide.
[005] Combinations containing different herbicide compositions 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. There are chemicals that act as non-selective herbicides which can be used to clear waste ground. No single molecule or composition is known to control all the weeds and not harm the agricultural/horticultural crops. In addition, a part of known herbicide has high toxicity, and many plants develop a resistance to the chemicals over time.
[006] 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
[001] In one aspect, the present invention discloses a synergistic herbicidal composition comprising pyrithiobac acid, its salts or combination thereof and a protoporphyrinogen oxidase (PPO) inhibitor.
[002] In another aspect, the present invention relates to a process of preparing the synergistic herbicidal composition of the present invention.
[003] 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 herbicidal composition of the present invention.
[004] In yet another aspect, the present invention relates to the use of the synergistic herbicidal composition in weed control in soil, a plant and/or propagation material thereof.

DETAILED DESCRIPTION OF THE INVENTION
[005] Discussed below are some representative embodiments of the present invention. The invention in its broader aspects is not limited to the specific details and representative methods. An illustrative example is described in this section in connection with the embodiments and methods provided.
[006] It is to be noted that, as used in the specification, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a composition containing “a compound” includes a mixture of two or more compounds. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[007] The expression of various quantities in terms of “%” or “% w/w” means the percentage by weight of the total solution or composition unless otherwise specified.
[008] The present invention discloses a synergistic herbicidal composition comprising at least two herbicides comprising an effective amount of pyrithiobac acid, its salt or combination thereof, a protoporphyrinogen oxidase (PPO) inhibitor and optionally comprising agrochemically acceptable excipient.
[009] In an embodiment, the herbicidal composition comprises 1 – 99 % w/w of protoporphyrinogen oxidase (PPO) inhibitor based on the total weight of the composition.
[010] In an embodiment, the herbicidal composition comprises 1 – 99 % w/w of pyrithiobac acid and its salts or combination thereof based on the total weight of the composition.
[011] In an embodiment, the herbicidal composition comprises protoporphyrinogen oxidase (PPO) inhibitor compound is preferably selected from a N-Phenyl-imide, its derivatives or combination thereof.
[012] The N-Phenyl-imide derivative compound is selected from, but not limited to, Butafenacil, Saflufenacil, Pentoxazone, Chlorphthalim, Cinidon-ethyl, Flumiclorac-pentyl, Flumioxazin, Flumipropyn, Trifludimoxazin, Tiafenacil herbicides. These compounds are used as post emergence herbicide known to control weeds such as Commelina benghalensis, Digera arvensis, Euphorbia spp., Phyllannthus niruri, Echinochloa crusgalli, Runnex spp., Medicago denticulate, Coronopus didymus, Chenopodium album, Phalaris minor, Avena fatua (more than 10 weed genera in various crops i.e., soyabean and wheat).
[013] In an embodiment, the herbicidal composition comprises protoporphyrinogen oxidase (PPO) inhibitor compound is preferably selected from Flumioxazin.
[014] In an embodiment, the herbicidal composition comprises pyrothiobac acid or its salt or combination thereof. The pyrothiobac acid and its salts are acetolactate synthase inhibitors used as early post emergence herbicide which controls Trianthema Spp, Amaranthus Spp, Chenopodium Spp, Digera Spp, Celosia argentia weeds (more than 5 weed in cotton).
[015] In a preferred embodiment of the present invention, the herbicidal composition comprises synergistically effective amount of pyrithiobac acid and Flumioxazin i.e. 1 - 99 % w/w of pyrithiobac acid and 1 – 99 % w/w Flumioxazin based on total wight of the composition.
[016] In yet another preferred embodiment, the herbicidal composition comprises 5 – 35 % w/w of pyrithiobac acid, its salt or combination thereof and 5 – 45 % w/w Flumioxazin based on the total weight of composition to achieve the synergistically effective herbicidal composition.
[017] In an embodiment, the composition optionally comprises agrochemically acceptable excipient selected from the group consisting of, but not limited to, 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, and clays and/or mixtures thereof. The agrochemically acceptable excipients in a pre-determined ratio aids to improving the physical stability and prevents the degradation of the composition leading to long term stability and wide spectrum activity. The employment of excipients used in the composition will depend upon the type of formulation and/or the manner in which the formulation is to be applied by the end user.
[018] In an embodiment the agrochemically acceptable excipients are selected from Polymethyl methacrylate-polyethylene glycol graft copolymer, Polyoxyethylene alkyl ether, Modified styrene acrylic co-polymer, Styrene (meth)acrylic copolymer, Ethoxylated polyarylphenol phosphate amine salt, Polyoxyethylene polyoxypropylene condensate, C12-16 ethoxylated alcholols, Formulated Nonionic ethoxylates or combination/mixture thereof.
[019] In an embodiment of the invention, the agrochemically acceptable excipients include styrene acrylate polymer at a concentration of at least 1 % w/w to 10 % w/w based on total weight of the composition, preferably 3 % w/w to 7 % w/w based on total weight of the composition.
[020] In an embodiment, the herbicidal composition can be formulated in any form known to a person skilled in the art selected from the group consisting of, but not limited to, Emulsifiable Concentrate (EC), 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) or powder for dry seed treatment (DS).
[021] In a preferred embodiment of the present invention, the herbicidal composition is formulated in the form of a Suspension Concentrate (SC) formulation. Typically, the herbicidal composition in the form of a ready-to use stable Suspension Concentrate (SC) formulation demonstrates synergistic effects with good physical and chemical stability.
[022] Another aspect of the present invention provides a process of preparing the herbicidal composition of the present invention. The process comprises the following steps:
a. charge propylene glycol to the homogenizer having demineralized water and mix at a low speed;
b. adding surfactants to the homogenizer and mixing to form a slurry;
c. adding agrochemically acceptable excipients to the slurry and mixing;
d. adding pre-weighed quantities of Pyrithiobac Sodium and Flumioxazin under continuous stirring to form a smooth slurry;
e. charging slurry form step d) to Dyno mill;
f. add required quantity of agrochemically acceptable excipients and stirring the slurry to obtain herbicidal composition.
[023] In an embodiment, the process comprises charging propylene glycol to the homogenizer having demineralized water and mix at a low speed of 100 rpm; adding surfactants polymethyl methacrylate-polyethylene glycol graft copolymer (Atlox 4913) and polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894) to the homogenizer and mix for 15 minutes to form a slurry; adding 1, 2 - Benzisothiazoline-3-one and Polydimethylsiloxane (SAG 1572) to the slurry and mix for 15 minutes; adding pre-weighed quantities of Pyrithiobac Sodium and Flumioxazin under continuous stirring to form a smooth slurry; charging slurry form step d) to Dyno mill to proper size reduction at 25?C; and adding required quantity of Precipitated Silica (Sipernat 22S) and Xanthan gum (Rhodopol 23/W) and stir the slurry for 3-4 hours to obtain suspension concentrate (SC) formulation.
[024] Yet another aspect of the present invention provides 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 herbicidal composition.
[025] Advantageously, the synergistic herbicidal composition demonstrates broad spectrum control of weed flora as an early post emergence herbicide to control more than 10 weed genera. Accordingly, the herbicidal composition is used to control weed species such as Commelina benghalensis, Digera arvensis, Euphorbia spp., Phyllannthus niruri, Echinochloa crusgalli, Runnex spp., Medicago denticulate, Coronopus didymus, Phalaris minor, Avena fatua, Trianthema Spp, Amaranthus Spp, Chenopodium Spp, Digera Spp, Celosia argentia or combination thereof.

EXAMPLES
[026] The following examples are illustrative of the present invention but not limitative of the scope thereof:
[027] Materials and Methods
[028] Materials: Pyrithiobac Sodium a.i., Flumioxazin a.i., Polymethyl methacrylate-polyethylene glycol graft copolymer (Atlox 4913), Polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894), Modified styrene acrylic co-polymer (Atlox 4917), Styrene (meth)acrylic copolymer (Atlox Metasperse™ 500L), Ethoxylated polyarylphenol phosphate amine salt (Soprophor FL), Polyoxyethylene polyoxypropylene condensate (Unitop - 203), C12-16 ethoxylated alcholols (Tersperse 4894), Formulated Nonionic ethoxylates (Tersperse 2288), Polydimethylsiloxane (SAG 1572), Xanthan Gum (2%)(Rhodopol 23/W), 1,2-propanediol (Propylene Glycol), 1,2 - Benzisothiazoline - 3 – one, Precipitated Silica (Sipernat 22S) and Water.
[029] Method: Six herbicidal SC formulations comprising the Pyrithiobac Acid and its salts, Flumioxazin and agrochemically acceptable excipients were prepared by the process comprising steps as follows: charging propylene glycol to the homogenizer having demineralized water and mix at a low speed of 100 rpm; adding surfactants polymethyl methacrylate-polyethylene glycol graft copolymer (Atlox 4913) and polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894) to the homogenizer and mix for 15 minutes to form a slurry; adding 1, 2 - Benzisothiazoline-3-one and Polydimethylsiloxane (SAG 1572) to the slurry and mix for 15 minutes; adding pre-weighed quantities of Pyrithiobac Sodium and Flumioxazin under continuous stirring to form a smooth slurry; charging slurry form step d) to Dyno mill to proper size reduction at 25?C; and adding required quantity of Precipitated Silica (Sipernat 22S) and Xanthan gum (Rhodopol 23/W) and stir the slurry for 3-4 hours to obtain suspension concentrate (SC) formulation.
[030] The composition of herbicidal SC formulations prepared according to the above-described method are provided in Table 1 as follows:

Table 1
S.No. Pyrithiobac Sodium
(% w/w) Flumioxazin (% w/w) Surfactants/Adjuvants/
Safener
(% w/w) Dose/Ha
(ml)

Formulation Example-1 24.00 40.00 36.00 250.00
Formulation Example-2 12.00 20.00 68.00 500.00
Formulation Example-3 10.00 30.00 60.00 400.00
Formulation Example-4 40.00 24.00 36.00 250.00
Formulation Example-5 20.00 12.00 68.00 500.00
Formulation Example-6 30.00 10.00 60.00 400.00

[031] The amounts of various ingredients used in the herbicidal SC formulations comprising the Pyrithiobac acid and its salts, Flumioxazin and agrochemically acceptable excipients is summarized in Tables 2-7 below.
[032] Formulation Example-1 (Pyrithiobac Sodium 24% + Flumioxazin 40%)
Table 2
Component Name % w/w
Pyrithiobac Sodium a.i. 24
Flumioxazin a.i. 40
Polymethyl methacrylate-polyethylene glycol graft copolymer (Atlox 4913) 5
Polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894) 3
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 5
1,2-propanediol (Propylene Glycol) 5
1,2 - Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[033] Formulation Example-2 (Pyrithiobac Sodium 12% + Flumioxazin 20%)
Table 3
Component Name % w/w
Pyrithiobac Sodium a.i. 12
Flumioxazin a.i. 20
Polymethyl methacrylate-polyethylene glycol graft copolymer (Atlox 4913) 4
Modi?ed styrene acrylic co-polymer (Atlox 4917) 3
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 10
1,2-propanediol (Propylene Glycol) 5
1,2 - Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[034] Formulation Example-3 (Pyrithiobac Sodium 10% + Flumioxazin 30%)
Table 4:
Component Name % w/w
Pyrithiobac Sodium a.i. 10
Flumioxazin a.i. 30
Styrene (meth)acrylic copolymer (Atlox Metasperse™ 500L) 4
Polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894) 2
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 10
1,2-propanediol (Propylene Glycol) 5
1,2 - Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[035] Formulation Example-4 (Pyrithiobac Sodium 40% + Flumioxazin 24%)
Table 5
Component Name % w/w
Pyrithiobac Sodium a.i. 40
Flumioxazin a.i. 24
Styrene (meth)acrylic copolymer (Atlox Metasperse™ 500L) 5
Polyoxyethylene alkyl ether (Nonionic proprietary surfactant blend) (Atlox 4894) 3
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 5
1,2-propanediol (Propylene Glycol) 5
1,2 - Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[036] Formulation Example-5 (Pyrithiobac Sodium 20% + Flumioxazin 12%)
Table 6
Component Name % w/w
Pyrithiobac Sodium a.i. 20
Flumioxazin a.i. 12
Ethoxylated polyarylphenol phosphate amine salt (Soprophor FL) 3
Polyoxyethylene polyoxypropylene condensate (Unitop - 203) 3
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 10
1,2-propanediol (Propylene Glycol) 5
1,2 - Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[037] Formulation-6 (Pyrithiobac Sodium 30% + Flumioxazin 10%)
Table 7

Component Name % w/w
Pyrithiobac Sodium a.i. 30
Flumioxazin a.i. 10
C12-16 ethoxylated alcholols (Tersperse 4894) 2
Formulated Nonionic ethoxylates (Tersperse 2288) 4
Polydimethylsiloxane (SAG 1572) 0.5
Xanthan Gum (2%)(Rhodopol 23/W) 10
1,2- propanediol (Propylene Glycol) 5
1,2- Benzisothiazoline - 3 – one 0.1
Precipitated Silica (Sipernat 22S) 0.5
Water q.s. to 100

[038] Efficacy Studies
[039] Field trials were performed to evaluate the efficacy of herbicidal SC formulations described above on annual grass control and dicot control in Cotton perennial crops.
[040] Cotton crops were grown on plots under natural outdoor conditions and the weed flora present in the field were preferably Commelina benghalensis, Digera arvensis, Euphorbia spp., Phyllannthus niruri, Echinochloa crusgalli, Runnex spp., Medicago denticulate, Coronopus didymus, Phalaris minor, Avena fatua, Trianthema Spp, Amaranthus Spp, Chenopodium Spp, Digera Spp, Celosia argentia at the 2-4 leaf stage.
[041] Herbicidal formulations of the invention in different doses as mentioned in Tables 2-4 were diluted with water to get desired solution having actives as presented in Table 8 and sprayed on cotton crops with weed flora present in the field. Further, Pyrithiobac Sodium and Flumioxazine were individually sprayed on the cotton crops with weed flora present in the field.
[042] The application on the cotton crops with weed flora present in the field was preferably as foliar spray at an application rate of 500 liters water per hectare using knapsack sprayer with flat fan nozzle. The number of individual weeds and total weeds present in the field was recorded at 15, 30 and 60 days after the application of the herbicidal formulations of the invention in comparison with untreated control. The total weed control efficacy at 30 days after treatment is shown in Table 8.
[043] 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. The ability of the compositions described herein to afford suitable weed control is illustrated by the efficacy data in Table 8.
[044] Total weed control efficacy influenced by various herbicidal SC formulations at 30 days after application in Cotton perennial crops at the 2-4 leaf stage is represented in Table 8 below.
Table 8
Dose rate
(gram a.i./ha) Total weed control efficacy at 30 DAT

Colby's Difference Synergism/ Antagonism/
Observed Efficacy in % (O) Calculated Efficacy in
% (E) (O-E) Additivity
Pyrithiobac Sodium Flumioxazine
40 0 72 NA NA NA
60 0 83 NA NA NA
62.5 0 88 NA NA NA
75 0 95 NA NA NA
0 100 63 NA NA NA
0 120 76 NA NA NA
0 125 89 NA NA NA
40 120 97 93.28 3.72 Synergism
60 100 99 93.71 5.29 Synergism
DAT: Days after treatment

[045] Highest weed control efficiency was recorded with the application of herbicidal SC formulations of the invention as compared to individual application of each active ingredient Pyrithiobac Sodium and Flumioxazine. Further the results clearly show that herbicidal composition according to the present invention demonstrated a synergistic increase in the spectrum of weed control in addition to reducing the time and labour in a weed management program.
[046] Further, the synergistic herbicidal composition exhibits extremely useful weed control efficiency and has no phytotoxic impact on soybean, wheat and cotton.
[047] 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 herbicidal composition comprising pyrithiobac acid, its salts or combination thereof and a protoporphyrinogen oxidase (PPO) inhibitor.
2. The herbicidal composition as claimed in claim 1, comprising 1 – 99 % w/w of protoporphyrinogen oxidase (PPO) inhibitor and 1 – 99 % w/w of pyrithiobac acid or its salts or combination thereof based on total weight of the composition.
3. The herbicidal composition as claimed in claim 1or 2, wherein the protoporphyrinogen oxidase (PPO) inhibitor is selected from Flumioxazin.
4. The herbicidal composition as claimed in claim 1, further comprising agrochemically acceptable excipients selected from carrier, defoamer, wetting agent, disintegrating agent, anti-caking agent, dispersing agent, anionic emulsifier, colorant, polymeric film forming agent, non-ionic emulsifier sticking agent, anionic surfactant, non-ionic surfactant, polymeric surfactant, oil, stabilizer, preservative, thickener, viscosity modifying agent, rheology modifying agent, anti-freezing agent, and mixtures thereof.
5. The herbicidal composition as claimed in claim 1, wherein said composition is in form of any of Emulsifiable Concentrate (EC), 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) or powder for dry seed treatment (DS).
6. The herbicidal composition as claimed in claim 1, wherein said composition is in form of Suspension Concentrate (SC) formulation.
7. The herbicidal composition as claimed in claim 1, wherein said composition affords control of weeds selected from a group consisting of Commelina benghalensis, Digera arvensis, Euphorbia spp., Phyllannthus niruri, Echinochloa crusgalli, Runnex spp., Medicago denticulate, Coronopus didymus, Phalaris minor, Avena fatua, Trianthema spp, Amaranthus spp, Chenopodium spp, Digera spp, Celosia argentia or combination thereof.
8. 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 herbicidal composition as claimed in claims 1 to 8.
9. A process of preparing herbicidal composition comprising the following steps:
a. charge propylene glycol to the homogenizer having demineralized water and mix at a low speed;
b. adding surfactants to the homogenizer and mixing to form a slurry;
c. adding agrochemically acceptable excipients to the slurry and mixing;
d. adding pre-weighed quantities of Pyrithiobac Sodium and Flumioxazin under continuous stirring to form a smooth slurry;
e. charging slurry form step d) to Dyno mill;
f. adding required quantity of agrochemically acceptable excipients and stirring the slurry to obtain the herbicidal composition.
10. Use of the synergistic herbicidal composition claimed in claims 1 to 8 for weed control in soil, a plant and/or propagation material thereof.
Dated this 7th day of February 2023.
Godrej Agrovet Limited
By their Agent & Attorney

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