Claims:1. A herbicidal combination comprising (A) metribuzin; (B) 2,4-D or its derivatives; and (C) pyrazosulfuron or its derivatives.
2. The combination as claimed in claim 1, wherein the 2,4-D or its derivatives are selected from the group consisting of 2,4-dichlorophenoxyacetic acid; ,4-D-ammonium; 2,4-D-butotyl; 2,4-D-2-butoxypropyl; 2,4-D-3-butoxypropyl; 2,4-D-butyl; 2,4-D-diethylamine; 2,4-D-dimethylamine; 2,4-D-diolamine; 2,4-D-dodecylamine; 2,4-D-ethyl; 2,4-D-2-ethylhexyl; 2,4-D-heptylamine; 2,4-D-isooctyl; 2,4-D-isopropyl; 2,4-D-isopropylamine; 2,4-D-lithium; 2,4-D-meptyl; 2,4-D-methyl; 2,4-D-octyl; 2,4-D-pentyl; 2,4-D-propyl; 2,4-D-sodium; 2,4-D-tefuryl; 2,4-D-tetradecylamine; 2,4-D-triethylamine; 2,4-D-tris(2-hydroxypropyl)amine; 2,4-D-trolamine and 2,4-D-choline.
3. The combination as claimed in claim 1 or claim 2, wherein the pyrazosulfuron or its derivatives are selected from the group consisting of pyrazosulfuron and pyrazosulfuron-ethyl.
4. A herbicidal composition comprising the combination as claimed in any one of the preceding claims along with agrochemically acceptable excipients.
5. The herbicidal composition as claimed in claim 4 in the form of a granular formulation.
6. The composition as claimed in claim 5 comprising about, or less than about, 1.0% pyrazosulfuron-ethyl by total weight of the composition.
7. The composition as claimed in any one of the claims 4 – 6 additionally comprising at least one dispersing agent, at least one binding agent, at least one wetting agent or at least one defoamer.
8. A method for controlling undesired weeds in sugarcane, said method comprising treating the locus at which said sugarcane is growing or is intended to be grown with a herbicidal combination comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a synergistically effective amount of pyrazosulfuron or its derivatives.
9. The method as claimed in claim 8 comprising treating the locus with a herbicidal composition comprising about, or less than about, 1.0% pyrazosulfuron-ethyl by total weight of the composition.
10. The method as claimed in claim 9 or claim 10 wherein said weed is selected from the group comprising monocotyledonous weeds of the genera: Echinochloa, Setaria, Panicum, Eleusine, Digitaria, Phleum, Cenchrus, Poa, Festuca, Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum, Agropyron, Cynodon, Monochoria, Fimbristylis, Sagittaria, Eleocharis, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis, Alopecurus, Apera; Dicotyledonous weeds of the genera: Sinapis, Lepidium, Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Commelina, Ageratum, Chenopodium, Urtica, Senecio, Euphorbia, Acanthospermum, Amaranthus, Portulaca, Ipomoea, Xanthium, Convolvulus, Ipomoea, Polygonum, Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum, Rorippa, Rotala, Lindernia, Lamium, Veronica, Abutilon, Emex, Datura, Viola, Galeopsis, Papaver, Centaurea, Trifolium, Ranunculus, Taraxacum; Cyperus and Scirpus.
, Description:Field of the invention:
The present invention relates to a herbicidal combination. More particularly, the present invention relates to a herbicidal combination useful against harmful weeds in crop plants, particularly in sugarcane.
Background of the invention:
Weeds cause 12 to 72% reduction in sugarcane yield depending upon the density of the weeds. The weed problem in sugarcane is further compounded due to the nature and practices in sugarcane cultivation. Sugarcane is planted with a wide row spacing, which provides more space for the weeds to flourish. The growth of sugarcane in the initial stages is very slow as it takes about15 to 20days to complete the germination and another 60 -75 days for developing the full canopy cover. During this 30 – 120 days period, the weeds get plenty of time to compete with sugarcane crop for nutrients, soil moisture, sunlight right from germination to growing stage and suppresses its growth and development. Sugarcane is also grown under abundant water and nutrient supply conditions, which encourages the weed infestation. Sugarcane cultivation also involves very little preparatory tillage. Therefore, the weeds once established tend to flourish well, which is further compounded due to the use of fertilizers.
Sugarcane is usually grown throughout the year. Therefore, it is also prone to being infested with a variety of weeds. The types of weeds which grow in sugarcane are monocotyledonous weeds of the genera: Echinochloa, Setaria, Panicum, Eleusine, Digitaria, Phleum, Cenchrus, Poa, Festuca, Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum, Agropyron, Cynodon, Monochoria, Fimbristylis, Sagittaria, Eleocharis, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis, Alopecurus, Apera, etc; Dicotyledonous weeds of the genera: Sinapis, Lepidium, Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Commelina, Ageratum, Chenopodium, Urtica, Senecio, Euphorbia, Acanthospermum, Amaranthus, Portulaca, Ipomoea, Xanthium, Convolvulus, Ipomoea, Polygonum, Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum, Rorippa, Rotala, Lindernia, Lamium, Veronica, Abutilon, Emex, Datura, Viola, Galeopsis, Papaver, Centaurea, Trifolium, Ranunculus, Taraxacumetc; Additionally, Cyperus, Scirpus, etc. among sedges are major weeds found in sugarcane.
Therefore, it is difficult to achieve weed control in sugarcane by following hand weeding or a specific weed management approach. It is therefore advisable to have a suitable combination of herbicides for more dependable, economical and desirable weed control.

Some common herbicides currently used for weed management in sugarcane are atrazine, oxyfluorfen, grammaxone + 2,4 – D, glyphosate and thiobencarb. Unfortunately, most of the available herbicides can control either one type of weeds i.e. either monocotyledonous weeds or dicotyledonous weeds. Moreover most of the herbicides do not protect the germination of weeds after killing of standing weeds therefore new weeds again emerge and start competing against the sugarcane. Moreover, the use of 2,4-D is discouraged when the neighbouring crop is cotton or okra. Thus, there is a need to find alternate herbicidal solutions for controlling the weed infestations in sugarcane.

WO2012141277 (A1) discloses a herbicidal composition comprising, as active ingredients, (a) flazasulfuron or its salt and (b) metribuzin or its salt. This publication further discloses that the herbicidal composition of this invention may be mixed with or may be used in combination with fungicides, antibiotics, plant hormones, insecticides, fertilizers, phytotoxicity-reducing agents, etc., whereby more excellent effects and activities may sometimes be obtained. A further additional herbicide, in addition to flazasulfuron and metribuzin, may be 2,4-D.

CN101077070 (A) discloses one kind of herbicide for treating soil to prevent and kill upland field weeds. The herbicide consists of three effective herbicide components, including metribuzin, acetochlor and 2,4-D, in the weight ratio of 3-6 to 30-40 to 5-20, preferably 5 to 37 to 18. The herbicide may be used in corn, soybean and potato fields, and has broad herbicidal spectrum, high herbicidal efficiency and no influence on intercropping, mixed cropping and rotation cropping.

US6242382 (B1) discloses a solid mixture comprising a) an active ingredient from the group of the sulfonylureas and b) an alkyl ether of a copolymer of C2-C4-alkylene oxides. The solid mixtures according to the invention may also comprise, in addition to components a) and b), other active ingredients which can be mixed with, or act synergistically with, sulfonylureas. Such products are known to those skilled in the art and described in the literature. The following groups of other active ingredients may be mentioned by way of example, using their INN: other active ingredients include metribuzin or 2,4-D. The amount of the other active ingredients c)--if present--is generally in a range of from 0.5 to 75, preferably of from 1 to 60% by weight of the formulation.

Metribuzin is a triazinone herbicide having the IUPAC name 4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one and structure:

Pyrazosulfuron-ethyl is a pyrimidinylsulfonyl urea herbicide having IUPAC name ethyl 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)sulfamoyl]-1-methylpyrazole-4-carboxylate:

It is a rice herbicide belonging to the sulfonylurea group of herbicides. It has eminent activity against a broad spectrum of annual and perennial rice paddy weeds, especially broadleaf weeds and sedges, with pre-emergence and early post-emergence applications at extremely low use rates.
2,4, D is a phenoxyacetic herbicide having IUPAC name as (2,4-dichlorophenoxy)acetic acid:

WO2015044150/WO2013089207, assigned to BASF Agrochemical Products BV and Sumitomo respectively, relate to a method for controlling weeds in a sugar cane field. The method involves the use of at least one herbicide selected from ametryn, atrazine, simazine, alachlor, metolachlor, S-metolachlor, asulam, metribuzin, trifluralin, pendimethalin, tebuthiuron, diuron, hexazinone, amicarbazone, imazapic, trifloxysulfuron sodium salt, iodosulfuron-methyl sodium salt, halosulfuron-methyl, ethoxysulfuron, carfentrazone-ethyl, isoxaflutole, bicyclopyrone, mesotrione, picloram and salts and esters thereof, 2,4-D and salts and esters thereof, dicamba and salts and esters thereof, clomazone, MSMA, paraquat, diquat, glufosinate, glufosinate ammonium salt, glufosinate-P and salts thereof, and glyphosate and salts thereof.A combination of 2,4-D and metribuzin only could have been possibly conceivable, without prejudice, following the teachings of these disclosures.
The efficacy of these herbicides against harmful plants in the crop plants is remarkable, but depends on the application rate, the formulation ingredients, the harmful weeds to be controlled, the climatic conditions and the soil conditions. Single application of the individual herbicide may lead to development of resistance in the target weeds and sometimes such resistance is developed even when a combination of herbicides is applied. In general, however, there remains a need for methods to achieve the herbicidal action at a lower application rate of active compounds. Not only does a lower application rate reduce the amount of an active compound required for application, but, it also reduces the amount of formulation auxiliaries required. It both reduces the economic input and improves the ecological compatibility of the herbicide treatment.
One way to improve the application profile of a herbicide can consist in combining the active compound with one or more other active compounds. However, while formulating one or more herbicides in a single composition, a formulator is faced by many problems such as physical, chemical and biological incompatibility, a lack of stability in a coformulation, decomposition of an active compound, or antagonism of the active compounds.
Therefore there is a need for combinations of active compounds having an advantageous activity profile, high stability and, a synergistically improved action, which allows the application rate to be reduced in comparison with the individual application of the active compounds to be combined.
In an embodiment, the present invention described hereinafter meets at least one such need in the art.
Summary of the Invention:
In an aspect, the present invention provides a herbicidal combination comprising (A) a herbicidally effective amount of metribuzin;(B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a herbicidally effective amount of pyrazosulfuron or its derivatives.
In another aspect, the present invention provides a herbicidal composition comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a herbicidally effective amount of pyrazosulfuron or its derivatives alongwith agrochemically acceptable excipients.
In an embodiment, the present invention provides an improved herbicidal combination for the control of undesired weeds in sugarcane, said combination comprising (A) a herbicidally effective amount of metribuzin; and (B) a herbicidally effective amount of 2,4-D or its derivatives; wherein the improvement comprises said combination additionally comprising (C) a synergistically effective amount of pyrazosulfuron or its derivatives.
In another embodiment, the present invention provides a method for controlling undesired weeds in sugarcane, said method comprising treating the locus at which said sugarcane is growing or is intended to be grown with a herbicidal combination comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a herbicidally effective amount of pyrazosulfuron or its derivatives.
Brief description of the invention:
Surprisingly, the present inventors have now found that when the combination of metribuzin and 2,4-D was mixed with a reduced amount of pyrazosulfuron ethyl, the resultant combination showed improved synergistic effect. It was surprising that even a reduced amount of pyrazosulfuron-ethyl, which is a conventional rice herbicide, resulted in unexpectedly enhancing the efficacy of a combination of metribuzin and 2,4-D, to a greater degree than expectable, for controlling undesired weeds in sugarcane.
Surprisingly, it has been found that the active compound combinations or compositions according to the invention do not only exhibit an additive effect of the activity of the individual components, but exert a synergistic effect when used in combination. Therefore, firstly, the customary application rates of the individual substances were reduced.
Therefore, in an aspect, the present invention provides herbicidal combination comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a herbicidally effective amount of pyrazosulfuron or its derivatives.
In an embodiment, the herbicides or the combinations thereof contemplated according to the present invention may be pre-formulated and may be in the form of granules, which may be Water Dispersible Granules (WDG) or Granules (G) for broadcasting, Wettable Powders, Suspension Concentrates, Emulsifiable Concentrate, Suspoemulsions, Microemulsions, Capsule Suspensions etc. However, the choice of any preferred formulation type is not particularly limiting.

Adjuvants and ancillary ingredients may be used to formulate such pre formulated compositions and may employ wetting agents, adhesives, dispersants, penetrants, rain-fastening agents or surfactants and, if appropriate, solvent or oil and other agriculturally acceptable additives and adjuvants.

Therefore, in another aspect, the present invention provides a herbicidal composition comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a herbicidally effective amount of pyrazosulfuron or its derivatives along with agrochemically acceptable excipients.
The compound 2,4-D or its derivatives shall include the compound 2,4-dichlorophenoxyacetic acid per se or any its derivatives including 2,4-D-ammonium; 2,4-D-butotyl; 2,4-D-2-butoxypropyl; 2,4-D-3-butoxypropyl; 2,4-D-butyl; 2,4-D-diethylamine; 2,4-D-dimethylamine; 2,4-D-diolamine; 2,4-D-dodecylamine; 2,4-D-ethyl; 2,4-D-2-ethylhexyl; 2,4-D-heptylamine; 2,4-D-isooctyl; 2,4-D-isopropyl; 2,4-D-isopropylamine; 2,4-D-lithium; 2,4-D-meptyl; 2,4-D-methyl; 2,4-D-octyl; 2,4-D-pentyl; 2,4-D-propyl; 2,4-D-sodium; 2,4-D-tefuryl; 2,4-D-tetradecylamine; 2,4-D-triethylamine; 2,4-D-tris(2-hydroxypropyl)amine; 2,4-D-trolamine and 2,4-D-choline.
In an embodiment, the preferred 2,4-D derivative is 2,4-D sodium.
The compound pyrazosulfuron or its derivatives shall include the compound 5-[(4,6-dimethoxypyrimidin-2-ylcarbamoyl)sulfamoyl]-1-methylpyrazole-4-carboxylic acid or an agriculturally acceptable salt or ester or a carboxylate salt thereof, including but not limited to, pyrazosulfuron-ethyl.
In an embodiment, the preferred pyrazosulfuron derivative is pyrazosulfuron-ethyl.
In an embodiment, metribuzin is present within the compositions in an amount of 5% to 70% by total weight of the composition.
In another embodiment, 2,4-D or its derivative is present within the compositions in an amount of 10% to 70%by total weight of the composition.
It has been one of the surprising findings of the present invention that when the combination of metribuzin and 2,4-D was mixed with a reduced amount of pyrazosulfuron-ethyl, the resultant combination showed improved synergistic effect. It was surprising that even a reduced amount of pyrazosulfuron-ethyl, which is a conventional rice herbicide, resulted in unexpectedly enhancing the efficacy of a combination of metribuzin and 2,4-D, to a greater degree than expectable, for controlling undesired weeds in sugarcane.
Thus, in this embodiment, the present invention provides an improved herbicidal combination for the control of undesired weeds in sugarcane, said combination comprising (A) a herbicidally effective amount of metribuzin; and (B) a herbicidally effective amount of 2,4-D or its derivatives; wherein the improvement comprises said combination additionally comprising (C) a synergistically effective amount of pyrazosulfuron or its derivatives.
The term synergistically effective amount of pyrazosulfuronor its derivatives means an amount of 0.1% to 5%by total weight of the composition.
In an embodiment of the present invention, the synergistically effective amount of pyrazosulfuron-ethyl comprises from about 0.1% to about 5% by total weight of the formulation. More preferably, the synergistically effective amount of pyrazosulfuron-ethyl according to the present invention comprise about 0.05% to about 4.0% by weight of pyrazosulfuron-ethyl. Still more preferably, the synergistically effective amount of pyrazosulfuron-ethyl according to the present invention comprise about, or less than about, 1.0% by total weight of the composition.
In an embodiment, the preferred composition according to the present invention is a granular formulation.
Therefore, in this embodiment, the present invention provides a granular formulation comprising:
(A) a herbicidally effective amount of metribuzin;
(B) a herbicidally effective amount of 2,4-D or its derivatives;
(C) a herbicidally effective amount of pyrazosulfuron or its derivatives; and
(D) at least one agrochemically acceptable solid inert.
In this embodiment, the granular formulation of the present invention further comprises an agrochemically acceptable inert. These inerts must be agriculturally acceptable and environmentally friendly. Inerts may include such dispersing agents, antifoaming agents, pH modifiers, surfactants, and other fillers which may be added to stabilize the composition.
In an embodiment, the composition of each or any aspect or embodiment described hereinabove comprises at least one dispersing agent, at least one binding agent, at least one wetting agent and optionally at least one defoamer.
In one embodiment, the composition may contain ionic and nonionic dispersing agents to enable disintegration of granules in water with ease, such as salts of polystyrenesulphonic acids, salts of polyvinylsulphonic acids, salts of naphthalenesulphonic acid/formaldehyde condensates, salts of condensates of naphthalenesulphonic acid, phenolsulphonic acid and formaldehyde, modified styrene acrylic copolymer and salts of lignosulphonic acid, polyethylene oxide/polypropylene oxide block copolymers, polyethylene glycol ethers of linear alcohols, reaction products of fatty acids with ethylene oxide and/or propylene oxide, furthermore polyvinyl alcohol, polyvinylpyrrolidone, copolymers of polyvinyl alcohol and polyvinylpyrrolidone and copolymers of (meth)acrylic acid and (meth)acrylic esters, furthermore alkyl ethoxylates and alkylarylethoxylates. The preferred dispersing agents include modified styrene acrylic copolymer.

In an embodiment, the compositions of the present invention comprise at least one wetting agent selected from soaps; salts of aliphatic monoesters of sulphuric acid including but not limited to sodium lauryl sulphate; sulfoalkylamides and salts thereof including but not limited to N-methyl-N-oleoyltaurate Na salt; alkylarylsulfonates including but not limited to alkylbenzenesulfonates; alkylnaphthalenesulfonates and salts thereof and salts of ligninsulfonic acid. In an embodiment, the wetting agent includes a blend comprising an alkali metal salt of alkylnaphthalenesulfonate or an alkali metal salt of ligninsulfonic acid or a combination thereof.

In a preferred embodiment, the composition of the present invention comprises a wetting component comprising a wetting agent selected from an alkali or alkaline earth metal salt of alkyl naphthalenesulfonate or an alkali metal salt of ligninsulfonic acid or a combination thereof.

In an embodiment, the compositions of the present invention comprise at least one antifoaming agent which is usually employed for this purpose in agrochemical compositions. In an embodiment, the preferred antifoaming agents are selected from aqueous emulsion with polysiloxane and emulsifier; silicone oil and magnesium stearate or a suitable combination thereof.
In preferred embodiment the present invention provides method of controlling broad spectrum of weeds at a locus by administering the locus with combinations of (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a synergistically effective amount of pyrazosulfuron or its derivatives.
Therefore, in this embodiment, the present invention provides a method for controlling undesired weeds in sugarcane, said method comprising treating the locus at which said sugarcane is growing or is intended to be grown with a herbicidal combination comprising (A) a herbicidally effective amount of metribuzin; (B) a herbicidally effective amount of 2,4-D or its derivatives; and (C) a synergistically effective amount of pyrazosulfuron or its derivatives.
In an embodiment, the locus may be the vicinity of any desired crop.
In a preferred embodiment, the desired crop is sugarcane.
In another preferred embodiment, the weed is selected from the group comprising nut sedge (Cyperusrotundus), flat sedge (Cyperusiria), Commelina (Commelinabenghalensis), morningglories (Ipomoea spp.), Chinese sprangletop (Leptochloachinensis) and Creeping grass (Brachiariareptans).
In another embodiment, the herbicidal combination/composition of the present invention was found especially effective against one or more of the following weeds infestations normally seen in sugarcane, such weeds include sedges – Cyprus rotundus; grasses – Cynodondactylon, Sorghum helepense, Panicum spp., Dactylocterniumaegyptium; broad leaved weeds – Chenapodium album, Convolvulus arvensis L., Amaranthusviridis L., Portulacaoleraceae L., Commmelinabengalensis L. and Trianthemaportulacastrum L.
In another embodiment, the herbicidal combination/composition of the present invention was found especially effective against one or more of the following weeds, which are normally found in sugarcane, namely weeds of the genera: Echinochloa, Setaria, Panicum, Eleusine, Digitaria, Phleum, Cenchrus, Poa, Festuca, Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum, Agropyron, Cynodon, Monochoria, Fimbristylis, Sagittaria, Eleocharis, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis, Alopecurus, Apera, etc; Dicotyledonous weeds of the genera: Sinapis, Lepidium, Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Commelina, Ageratum, Chenopodium, Urtica, Senecio, Euphorbia, Acanthospermum, Amaranthus, Portulaca, Ipomoea, Xanthium, Convolvulus, Ipomoea, Polygonum, Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum, Rorippa, Rotala, Lindernia, Lamium, Veronica, Abutilon, Emex, Datura, Viola, Galeopsis, Papaver, Centaurea, Trifolium, Ranunculus, Taraxacumetc; Additionally, Cyperus, Scirpus, etc. among sedges are major weeds found in sugarcane.
The invention will now be explained in more detail in the following examples that illustrate, but are not intended to limit, the invention.
EXAMPLES:
Example 1) : Wettable granules:
Sr. No Ingredients Amount (%) Function/Role of ingredients
1 2,4-D sodium salt 44 Active Ingredient
2 Metribuzin 35 Active Ingredient
3 Pyrazosulfuron-ethyl 1 Active Ingredient
4 Modified styrene acrylic polymers 5-6 Dispersant & binder
5 Sodium alkylnaphthalenesulfonate 2-3 Wetting agent
6 Aqueous emulsion with Polysiloxane and emulsifier 0.5 Defoam

Examples 2 – 7:
The following exemplary formulations were prepared:

WG formulations
#2 # 3 # 4 # 5 # 6 #7
1 2,4-D sodium salt 47 60 55 30 60 45
2 Metribuzine 37 30 35 60 25 35
3 Pyrazosulfuron-ethyl 1.1 2.5 1.5 0.5 4 4
4 Sodium salt of naphthalene sulfonate condensate - 5 - - - 2.5
5 Copolymer of styrene and sodium methacrylate - - 4 - - -
6 Hydrophobically modified polyacrylate copolymer - - - - - 10
7 Modified styrene acrylic copolymer 10.4 0 0 6 8 0
8 Sodium alkyl naphthalene sulfonate blend 4 2 4 0 2.5 0
9 Dialkyl naphthalene sulfonate sodium salt - - - 3 - 3
10 Silicone antifoam emulsion 0.5 0.5 0.5 0.5 0.5 0.5
Total 100 100 100 100 100 100

Examples 8 -10:
The following exemplary liquid formulations were prepared:
#8 # 9 # 10
1 2,4-D Ethylester 30 - -
2 2,4-DButyl ester - 35 25
2 Metribuzine 20 25 20
3 Pyrazosulfuron-ethyl 2 1.5 3
4 Polysorbate 80 - - 7.5
5 Alkyl EO/PO copolymer 2 0.5 0
6 Ethoxylatedisodecyl alcohol 6 5 3.5
7 Linear calcium dodecyl benzene sulfonate 0 2 1.5
8 Aromatic light naphtha solvent 20 20 19.5
9 poly ethylene glycol 20 11 20
Total 100 100 100

Field Trials:
Field trials were located in Haryana (India) and carried out under normal sugarcane crop cultivation conditions. The Sugarcane crop was grown using normal cultural practices for fertilization, irrigation, seeding, and maintenance to ensure good growth of the crop and the weeds. The trials were conducted using normal research methodology under sufficient weed pressure in the trial fields. The trial sites had naturally occurring populations of weeds. Trial plots were kept 5 meters (m) wide by 10 m long. All treatments were applied using a randomized complete block trial design with 3 replications per treatment. The weed spectrum included in the trials field, but was not limited to, was nut sedge (Cyperusrotundus), flat sedge (Cyperusiria), Commelina (Commelinabenghalensis), morningglories (Ipomoea spp.),Chinese sprangletop (Leptochloachinensis), Creeping grass (Brachiariareptans).
The herbicidal active compounds Pyrazosulfuron-ethyl (A), Metribuzin (B) and 2,4-D Sodium salt (C) were applied individually and in combinations using a hand pumped backpack sprayer fitted with flood jet nozzle and a spray volume of 500 liters per hectare (L/ha). Treatments were applied at 25 to 30 days after sowing in different trials.
The treated plots were observed for weed control by the herbicidal treatments with reference to a scale of 0% to 100% in comparison with untreated control plots, where 0 meant no damage and 100 meant complete destruction of the harmful plants.
Colby's equation was used to determine the herbicidal effects expected from the mixtures (Colby, S.R. Weeds 1967, 15, 20-22.m, Calculation of the synergistic and antagonistic response of herbicide combinations).
The following formula was used to calculate the expected activity of mixtures containing active ingredients, A and B:
Expected (E) A + B - AB
100
where
A = observed efficacy of active ingredient (combination of 2,4-D + metribuzin) A at the same concentration as used in the mixture.
B = observed efficacy of active ingredient B (pyrazosulfuron-ethyl) at the same concentration as used in the mixture.

The herbicide tank mix combinations, application rates, plant species tested, and results are given in Table 1 to 3.
Table 1: Synergistic control of Cyprus rotundus and Cyprus iris following post emergence application of Pyrazosulfuron-ethyl (B), Metribuzin and 2,4-D Sodium salt (A):

Trt.No
Active Ingredient/Product Application rate (g.a.i/ha) % control of
Cyprus rotundus % control of
Cyprus iria
B A B A Observed value (%) Expected value (%) Observed value (%) Expected value (%)
1 Pyrazosulfuron Ethyl - - 20 - - 54 - 61 -
2 Pyrazosulfuron Ethyl - - 30 - - 60 - 68 -
3 Pyrazosulfuron Ethyl - - 40 - - 68 - 75 -
4 - Metribuzin 2,4-D Sodium salt - 700 880 44.0
- 59.0
-
5 - Metribuzin 2,4-D Sodium salt - 1050 1320 48.0
- 56.0
-
6 - Metribuzin 2,4-D Sodium salt - 1400 1760 56.0
- 60.0
-
7 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 20 700 880 82 74.2 (+7.8) 92 84.0 (+8.0)
8 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 30 1050 1320 91 79.2 (+11.8) 100 85.9 (+14.1)
9 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 40 1400 1760 94 85.9 (+8.1) 100 90.0 (+10.0)

-Figures in ( ) are difference in Observed value vs Expected value; g a.i./ha - grams of active ingredient per hectare.
In the Colby method, the expected (or predicted) response of a combination of herbicides is calculated by taking the product of the observed response for each individual component of the combination when applied alone divided by 100 and subtracting this value from the sum of the observed response for each component when applied alone. An unexpected enhancement in efficacy of the combination is then determined by comparing the observed response of the combination to the expected (or predicted) response as calculated from the observed response of each individual component alone. If the observed response of the combination is greater than the expected (or predicted) response, or stated conversely, if the difference between the observed and expected response is greater than zero, then the combination is said to be synergistic or unexpectedly effective.
Thus, when the combination of the present invention was analyzed using this method, it demonstrated an observed – expected value of greater than zero which is indicative of an unexpected efficacy. The basis of demonstration of unexpected efficacy by comparison with the Colby formula is that herbicide (A) tested alone would kill a proportion of the target weeds and leave the remaining portion (a%) as survivors. Similarly, herbicide B tested alone will leave (b%) as survivors. When combined, A+B will, act independently on the target weed (if unexpected activity is absent); component A leaving a% survivors, which survivors will be controlled by component B; which has an overall effect of a%*b%*100. Subsequently, if the percent control is greater than that predicted by the Colby formula or stated conversely, if the difference between the observed control and the expected control is greater than zero; then unexpected enhancement in activity is acknowledged. The degree to which the difference is greater than zero is not itself critical as long as it is greater than zero; however greater the difference, more significant is the enhancement or the unexpectedness in weed control.
Table 2: Synergistic control of Leptochloachinensis and Brachiariareptans following post emergence application of Pyrazosulfuron-ethyl (A), Metribuzinand 2,4-D Sodium salt (B)

Trt.No
Active Ingredient/Product Application rate (g.a.i/ha) % control of
Leptochloachinensis % control of
Brachiariareptans
A B A B Observed value (%) Expected value (%) Observed value (%) Expected value (%)
1 Pyrazosulfuron Ethyl - - 20 - - 23 - 20 -
2 Pyrazosulfuron Ethyl - - 30 - - 28 - 21 -
3 Pyrazosulfuron Ethyl - - 40 - - 31 - 23 -
4 - Metribuzin 2,4-D Sodium salt - 700 880 71
- 80
-
5 - Metribuzin 2,4-D Sodium salt - 1050 1320 78
- 87

6 - Metribuzin 2,4-D Sodium salt - 1400 1760 84
- 94
-
7 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 20 700 880 86 77.7 (+8.30) 91 84.0 (+7.00)
8 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 30 1050 1320 98 84.2 (+13.8) 100 89.7 (+10.30)
21 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 40 1400 1760 99 89.0 (+10.0) 100 95.4 (+4.60)

-Figures in ( ) are difference in Observed value vs Expected value; ga.i./ha – grams of active ingredient per hectare.
Thus, when the combination of the present invention was analyzed using this method, it demonstrated an observed – expected value of greater than zero which is indicative of an unexpected efficacy.
Table 3: Synergistic control of Ipomoea spp. and Commelinabenghalensis following post emergence application of Pyrazosulfuron ethyl (A), Metribuzin and 2,4-D Sodium salt (B):

Trt.No
Active Ingredient/Product Application rate (g.a.i/ha) % control of
Ipomoea spp. % control of
Commelinabenghalensis
A B C A B C Observed value (%) Expected value (%) Observed value (%) Expected value (%)
1 Pyrazosulfuron Ethyl - - 20 - - 22 - 17 -
2 Pyrazosulfuron Ethyl - - 30 - - 29 - 21 -
3 Pyrazosulfuron Ethyl - - 40 - - 36 - 25 -
4 - Metribuzin 2,4-D Sodium salt - 700 880 74
- 81
-
5 - Metribuzin 2,4-D Sodium salt - 1050 1320 78
- 88
-
6 - Metribuzin 2,4-D Sodium salt - 1400 1760 83
- 91
-
7 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 20 700 880 88 79.7 (+8.30) 93 84.2
(+ 8.80)
20 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 30 1050 1320 97 84.4 (+12.6) 100 84.5 (+15.5)
21 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 40 1400 1760 98 89.1 (+8.90) 100 93.2 (+6.80)

- Figures in ( ) are difference in Observed value vs Expected value; g a.i./ha - grams of active ingredient per hectare.

Thus, when the combination of the present invention was analyzed using this method, it demonstrated an observed – expected value of greater than zero which is indicative of an unexpected efficacy.
Example 2.
Sugarcane sets were planted in the field to conduct a trial to assess phytotoxicity effect of herbicidal active compounds Pyrazosulfuron-ethyl (A), Metribuzin and 2,4-D Sodium salt (B) combination individually and in combination according to the instant invention. The trial was laid out in Randomized Black Design (RBD) with twenty two treatments including untreated control, replicated three times. For each treatment plot size of 30 sq.m was maintained. To raise the crops, all the agronomical practices were followed as usually adopted for sugarcane cultivation. The test herbicidal active compounds Pyrazosulfuron-ethyl (A), Metribuzin and 2,4-D Sodium salt(B) were applied individually and in combinations in the formulation in which they are present as commercially available product in market using a hand pumped backpack sprayer fitted with flood jet nozzle and a spray volume of 500 liters per hectare (L/ha). Untreated control plot was also sprayed by 500 l /ha water without adding any herbicides.
Observation on phytotoxicity viz growth stunting, was recorded at 15 and 30 days after application of treatments from ten plants which were randomly selected from each plot.

Table 4: Lower phytotoxic effect on sugarcane by tank mix application of Pyrazosulfuron-ethyl (A), Metribuzin (B) and 2,4-D Sodium salt (C) as compared to individual effect on crop.

Trt.No
Active Ingredient/Product Application rate (g.a.i/ha) % stunted growth
A B C A B C 15 DAS 30 DAS
1 Pyrazosulfuron Ethyl - - 20 - - 10 7
2 Pyrazosulfuron Ethyl - - 30 - - 15 9
3 Pyrazosulfuron Ethyl - - 40 - - 19 12
4 - Metribuzin 2,4-D Sodium salt - 700 880 9 6
5 - Metribuzin 2,4-D Sodium salt - 1050 1320 11 8
6 - Metribuzin 2,4-D Sodium salt - 1400 1760 15 9
7 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 20 700 880 6 2
8 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 30 1050 1320 7 3
9 Pyrazosulfuron Ethyl Metribuzin 2,4-D Sodium salt 40 1400 1760 10 5
10 Untreated - - - - - - -
ga.i./ha - grams of active ingredient per hectare
Results: Plants exposed to herbicidal active containing only Pyrazosulfuron-ethyl (A) and Metribuzin and 2,4-D in combination (B) showed a higher level of stunting than plants exposed to a combination of Pyrazosulfuron ethyl, Metribuzinand 2,4-D Sodium salt.