FIELD OF THE INVENTION

The present invention relates to synergistic herbicidal compositions. More particularly, the present invention relates to synergistic herbicidal compositions comprising Metribuzin and 2,4-dichlorophenoxyacetic acid (2,4-D), or an agriculturally acceptable salt or ester thereof.

BACKGROUND OF THE INVENTION

This section includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the present invention, or that any publication specifically or implicitly referenced is prior art.

Weeds are plants that are considered unwanted when they grow in a human controlled settings like farm fields, gardens, lawns, parks etc. As weeds reproduce quickly and can survive in almost any type of conditions they pose a threat to the yield of crops as they compete with crops for sunlight, nutrients, water etc. supplied to crops. Weeds also provide hosts and vectors for plant pathogens thereby giving them the opportunity to infect and degrade the quality of the products produced by the crops. They also provide food and shelter to various pests which are detrimental to the produce of crops.

Many recurring problems in agriculture involve controlling growth of undesirable vegetation that can, for instance, inhibit crop growth. A wide range of active herbicide compounds have been developed and used to control weeds in the agricultural industry. These active herbicide compounds are commercially available in various forms. While some of these active herbicide compounds are partially successful, their efficacy is limited in controlling certain weeds and the problem of controlling a broad spectrum of weeds still exists. In addition, many herbicidal formulations presently on the market are used in relatively high concentrations and volumes which cause high cost, phytotoxic problem, damage to desirable plant species and their residues detrimental to the succeeding crop.

In some cases, herbicidal active compounds have been shown to be more effective in combination than when applied individually and this is referred to as “synergism”. As described in the Herbicide Handbook of the Weed Science Society of America, Eighth Edition, 2002, p.462, “synergism is an interaction of two or more factors such that the effect when combined is greater than the predicted effect based on the response to each factor applied separately.”

To help control undesirable vegetation, researchers have produced a variety of chemicals and chemical formulations effective in controlling such unwanted growth. However, a continuing need exists for new compositions and methods to control growth of undesirable vegetation. Especially, in view of the environmental concern and to achieve results in very economical way, various attempts have been made to maximizing the performance of known active ingredients. There is thus a need in the art for a new and improved herbicide formulation which in combination exhibit excellent herbicidal activity towards target weeds, exhibits a very strong herbicidal activity to a wide range of agricultural weeds even at a low concentration, better selectivity, lower undesirable impact, lower production and market cost etc. The present invention satisfies the existing needs, as well as others, and generally overcomes the deficiencies found in the prior art.

The prior art teaches individual formulation of Metribuzin especially in wettable powder form and 2,4-D especially in soluble powder form and emulsifiable concentrate form. However, the existing arts do not disclose the particular combination of Metribuzin and 2,4-D or an agriculturally acceptable salt or ester thereof, nor do they disclose the concentration ranges and the ratios which shows synergistic effect. In view thereof, there is a need of herbicidal composition comprising Metribuzin and 2,4-D or an agriculturally acceptable salt or ester thereof which provides improved herbicidal properties at lower concentration as compared to that observed with the individual components.

SUMMARY OF THE INVENTION

The present invention relates to synergistic herbicidal composition for achieving effective and economical control of undesired weeds. It has unexpectedly found that composition comprising a Metribuzin and 2,4-D or its derivatives leads to much better control of the different weeds in comparison to the individual formulations. This considerably reduces the use of individual active ingredients in the combination formulations. Consequently, the toxic effects of the residues of the active ingredients on the biotic and abiotic part of the ecosystem are minimized.

The features of the invention will become more apparent from the detailed description set forth herein below.

DETAILED DESCRIPTION OF THE INVENTION

The following is a description of embodiments of the present invention. The embodiments are in such details as to clearly communicate the invention. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art.
Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including”, but not limited to.”

As used in the description herein and throughout the claims that follow, the meaning of “a”, “an” and “the” includes plural reference unless the context clearly dictates otherwise.

In some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment.

As used herein, the term "herbicide" or related terms means capable of being toxic to a plant (e.g., a weeds), controlling a plant, killing a plant, inhibiting the growth of a plant, and/or inhibiting the reproduction of a plant.

As used herein, the term "weed" means any plant targeted for treatment with a formulation of the invention. Target plants can be nuisance, unwanted, noxious, weedy, invasive, or harmful plant or vegetation (e.g., harmful to animals, harmful to ornamental plants, crops, etc.).

In accordance with an embodiment of the invention, the active ingredients/compounds used in the present invention are in the form of a free acid, salt, or an ester.

In accordance with an embodiment of the invention, a synergistic herbicidal composition comprising metribuzin, 2,4-D or/and its derivatives and at least one agriculturally acceptable adjuvant.

In accordance with an embodiment of the invention, the 2,4-D derivatives are selected from 2,4-D-ammonium, 2,4-D-butoyl, 2,4-D-2-butoxypropyl, 2,4-D-3-butoxypropyl, 2,4-D-butyl, 2,4-D-choline, 2,4-D-diethylammonium, 2,4-D-dimethylammonium, 2,4-D-diolamine, 2,4-D-dodecylammonium, 2,4-D-ethyl, 2,4-D-2-ethylhexyl, 2,4-D-heptylammonium, 2,4-D-isobutyl, 2,4-D-isoctyl, 2,4-D-isopropyl , 2,4-D-isopropylammonium, 2,4-D-lithium, 2,4-D-meptyl , 2,4-D-methyl, 2,4-D-octyl, 2,4-D-pentyl, 2,4-D-potassium, 2,4-D-propyl, 2,4-D-sodium, 2,4-D-tefuryl, 2,4-D-tetradecylammonium, 2,4-D-triethylammonium, 2,4-D-tris(2-hydroxypropyl)ammonium and/or 2,4-D-trolamine.

In accordance with one of the preferred embodiment of the invention, the 2,4-D derivative is 2,4-D-sodium.

In accordance with an embodiment of the invention, weight ratio of Metribuzin and 2,4-D or/and its derivatives is in a range from about 1:1 to 1:12.

In accordance with an embodiment of the invention, the metribuzin is present in an amount of 5-30 % by weight of the formulation.

In accordance with an embodiment of the invention, the 2,4-D or/and its derivatives is present in an amount of 20-60 % by weight of the formulation.

In accordance with an embodiment of the invention, the composition is formulated as a wettable powder (WP), suspension concentrate (SC), a micro emulsion (ME), an encapsulated suspension (CS), or a water dispersible granule (WG).

In accordance with an embodiment of the invention, all composition of the present invention comprising Metribuzin and 2,4-D or an agriculturally acceptable salt or ester thereof also contain one or more agriculturally acceptable adjuvant. The agriculturally acceptable adjuvant employed 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. Suitable auxiliaries which may be comprised in the composition according to the invention are all customary formulation adjuvants or components, such as extenders, carriers, solvents, surfactants, stabilizers, anti-foaming agents, anti-freezing agents, preservatives, antioxidants, colorants, thickners, solid adherents and inert fillers.

In accordance with one of the preferred embodiment of the invention, the composition is formulated as a wettable powder (WP).

In accordance with an embodiment of the invention, the agriculturally acceptable adjuvant in wettable powder (WP) form is selected from the group consisting of wetting agent, dispersing agent, binder, spreader, rheology modifier and inert carrier.

In accordance with an embodiment of the invention, in wettable powder (WP) form, wetting agent is blend of linear alkyl, a-olefin, aliphatic alcohol sulfonate, dispersing agent is blend of alkyl aryl naphthalene sulfonate, binder is sodium lignosulphonate, spreader is trisiloxane ethoxylate, rheology modifier is silica and inert carrier is lavigated china clay.

The herbicidal composition of the present invention may also comprise further active ingredients such as other herbicides and /or insecticides.

The following examples of formulations according to the invention are presented to illustrate, but not to restrict, this invention:

FORMULATION EXAMPLES

A wettable powder (WP) formulation of Metribuzin and 2,4-D sodium salt was prepared having the composition summarized in the following Table:

Ingredient Concentration (% w/w)
Metribuzin tech. 17.8 (16.8% a.i.)
2,4-D sodium salt tech. 60 (56 % a.i.)
Blend of linear alkyl, a-olefin, aliphatic alcohol sulfonate (Ginasul 46P) 2.5
Blend of alkyl aryl naphthalene sulfonate (Dispertox BS) 4.0
Sodium lignosulphonate (High molecular weight) 1.0
Trisiloxane ethoxylate 2.0
Silica 8.0
Lavigated china clay 4.7

Trisiloxane ethoxylate 2.0 parts by weight were blended with 8.0 parts by weight of silica. To this was added 17.87 parts by weight of Metribuzin tech. (16.8% a.i.), 4.0 parts by weight of dispersing agent i.e. blend of alkyl aryl naphthalene sulfonate, 60.0 parts by weight of 2,4-D sodium tech (56 % a.i.), 2.5 parts by weight of wetting agent i.e. blend of linear alkyl, a-olefin, aliphatic alcohol sulfonate, 1.0 parts by weight of sodium lignosulfonate and 4.7 parts by weight of lavigated china clay. The material was homogenized and micronized in air classifying mill or air jet mill to achieve particle size D90 less than 30 micron.

In the field of agriculture, it is often understood that the term “synergy” is as defined by Colby S.R. in an article entitled “Calculation of the synergistic and antagonistic responses of herbicide combinations” published in the journal Weeds, 1967, 15, p. 20-22. The action expected for a given combination of two active components can be calculated as follows:

E = X + Y – XY/100

Where,

E = Expected percentage of insecticidal control for the combination of the two insecticides at defined doses (for example equal to x and y respectively),

X = the percentage of insecticidal control by the compound (I) at a defined dose (equal to x),

Y = the percentage of insecticidal control by the compound (II) at a defined dose (equal to y),

When the percentage of observed insecticidal control for the combination is greater than the expected percentage, there is a synergistic effect.

The compositions of the present invention comprising metribuzin and 2,4-D or/and its derivatives are tested to evaluate the bio-efficacies for the control of various weeds such as grassy weeds (Dactyloctenium aegyptium, Echinochloa sp., Eleusin indica), sedges weeds (Cyperus rotundus), broad leaf Weeds (Chenopodium album, Convolvulus arvensis, Portulaca oleracea, Amaranthus virdis) and the expected efficacies for active ingredient combinations were determined using Colby’s formula and compared with observed efficacies. It was concluded that combination of Metribuzin and 2,4-D or/and its derivatives of the present invention demonstrate synergistic effect against weeds.

For example, field experiments were conducted to evaluate combination of Metribuzin 16.8% + 2,4-D sodium salt 56% WP @ 525 + 1750 a.i. g/ha against Sugarcane weed complex, compared with standard check Metribuzin 70% WP @ 525 a.i. g/ha and 2,4-D Sodium salt 80% WP @ 1750 a.i. g/ha, all the herbicides applied as post emergence. The expected efficacies for active ingredient combinations were determined using Colby’s formula and compared with observed efficacies. Table 1 as given herein below shows that the actions of active ingredients metribuzin and 2,4 D sodim Salt in combination is greater than the sum of the actions of the individual components i.e. Metribuzin and 2,4 D Sodim Salt and thus it was concluded that said combination demonstrate synergistic effect against weeds.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto.

S.No. Product a.i.
( g /ha) Observed Weed control Percentage (Percent control 20 Days after application)
Grassy Weeds Sedges Weed Broad leaf Weeds
Dactyloctenium aegyptium Echinochloa sp. Eleusin indica Cyperus rotundus Chenopodium album Convolvulus arvensis Portulaca oleracea Amaranthus virdis
1 Metribuzin 70% WP
525 61.9 56.6 66.9 38.2 53.9 54.4 50.0 50.7
2 2,4-D Sodium salt 80% WP
1750 0.0 0.0 0.0 65.5 67.3 68.9 65.7 69.8
3 Metribuzin 16.8% + 2,4-D sodium salt 56% WP
525 + 1750 77.5 87.6 74.3 83.2 87.2 90.1 88.9 85.8
Calculated/Expected Weed control Percentage by Colby’s formula
4 Metribuzin 16.8% + 2,4-D sodium salt 56% WP
525 + 1750 61.86 56.59 66.92 78.68 84.93 85.83 82.86 85.09

Table 1: Experiments conducted to determine observed weed control percentage and comparison is done with calculated percentage weed control to determine synergistic effect present for the composition comprising Metribuzin and 2,4-D sodium salt.

We Claim:

1. A synergistic herbicidal composition comprising:
(a) Metribuzin;
(b) 2,4-D or/and its derivatives; and
(c) at least one agriculturally acceptable adjuvant.

2. The synergistic herbicidal composition as claimed in claim 1, wherein the 2,4-D derivatives are selected from 2,4-D-ammonium, 2,4-D-butyl, 2,4-D-2-butoxypropyl, 2,4-D-3-butoxypropyl, 2,4-D-butyl, 2,4-D-choline, 2,4-D-diethylammonium, 2,4-D-dimethylammonium, 2,4-D-diolamine, 2,4-D-dodecylammonium, 2,4-D-ethyl, 2,4-D-2-ethylhexyl, 2,4-D-heptylammonium, 2,4-D-isobutyl, 2,4-D-isoctyl, 2,4-D-isopropyl , 2,4-D-isopropylammonium, 2,4-D-lithium, 2,4-D-meptyl , 2,4-D-methyl, 2,4-D-octyl, 2,4-D-pentyl, 2,4-D-potassium, 2,4-D-propyl, 2,4-D-sodium, 2,4-D-tefuryl, 2,4-D-tetradecylammonium, 2,4-D-triethylammonium, 2,4-D-tris(2-hydroxypropyl)ammonium and/or 2,4-D-trolamine.

3. The synergistic herbicidal composition as claimed in claim 2, wherein the 2,4-D derivative is 2,4-D-sodium.

4. The synergistic herbicidal composition as claimed in any of the preceding claims, wherein weight ratio of Metribuzin and 2,4-D or/and its derivatives is in a range from about 1:1 to 1:12.

5. The synergistic herbicidal composition as claimed in any of the preceding claims, wherein the metribuzin is present in an amount of 5-30 % by weight of the formulation.

6. The synergistic herbicidal composition as claimed in any of the preceding claims, wherein the 2,4-D or/and its derivatives is present in an amount of 20-60 % by weight of the formulation.

7. The synergistic herbicidal composition as claimed in any of the preceding claims, wherein the composition is formulated as a wettable powder (WP), suspension concentrate (SC), a micro emulsion (ME), an encapsulated suspension (CS), or a water dispersible granule (WG).

8. The synergistic herbicidal composition as claimed in any of the preceding claims, wherein the composition is formulated as a wettable powder (WP).

9. The synergistic herbicidal composition as claimed in claim 8, wherein said agriculturally acceptable adjuvant is selected from the group consisting of wetting agent, dispersing agent, binder, spreader, rheology modifier and inert carrier.

10. The synergistic herbicidal composition as claimed in claim 9, wherein said wetting agent is blend of linear alkyl, a-olefin, aliphatic alcohol sulfonate, dispersing agent is blend of alkyl aryl naphthalene sulfonate, binder is sodium lignosulphonate, spreader is trisiloxane ethoxylate, rheology modifier is silica and inert carrier is lavigated china clay.