Synergistic herbicidal composition and method of use thereof

A synergistic herbicidal composition comprising atrazine and either NMSC (i.e., 2-(2'-nitro-4'-methylsulfonylbenzoyl)-1,3-cyclohexanedione), or NMSOC (i.e., 2-(2'-nitro-4'-methylsulfonyloxybenzoyl)-1,3-cyclohexanedione): ##STR1## Also disclosed is a method of controlling undesirable vegetation by applying an effective amount of such composition to the locus of the vegetation to be controlled.

FIELD OF THE INVENTION 
In one aspect the present invention is directed to a synergistic herbicidal 
composition comprising (a) 
2-(2'-nitro-4'-methylsulfonylbenzoyl)-1,3-cyclohexanedione or 
2-(2'-nitro-4'-methylsulfonyloxybenzoyl)-1,3-cyclohexanedione; and (b) 
2-chloro-4-ethylamino-6-isopropylamino-S-triazine. In another aspect, the 
present invention is directed to a method of controlling the growth of 
undesirable vegetation by applying an herbicidally effective amount of 
such synergistic composition to the locus of such vegetation. 
BACKGROUND OF THE INVENTION 
The protection of crops from weeds and other vegetation which inhibit crop 
growth is a constantly recurring problem in agriculture. To help combat 
this problem, researchers in the field of synthetic chemistry have 
produced an extensive variety of chemicals and chemical formulations 
effective in the control of such unwanted growth. Chemical herbicides of 
many types have been disclosed in the literature and a large number are in 
commercial use. 
In some cases, active herbicides have been shown to be more effective in 
combination than when applied individually. The result is often termed 
"synergism", since the combination demonstrates a potency or activity 
level exceeding that which it would be expected to have, based on a 
knowledge of the individual potencies of the components. The present 
invention resides in the discovery that certain cyclohexanediones and 
2-chloro-4-ethylamino-6-isopropylamino-S-triazine(atrazine), already known 
individually for their herbicidal potency, display a synergistic effect 
when applied in combination. 
The compounds forming the combination which is the subject of the present 
invention are independently known in the art for their effects on plant 
growth. Thus, 2-chloro-4-ethylamino-6'-isopropylamino-S-triazine, commonly 
known as atrazine, is commercially sold under various trade names, and is 
described in the Herbicide Handbook of the Weed Science Society of 
America, 5th Edition, 1983; 
2-(2'-nitro-4'-methylsulfonylbenzoyl)-1,3-cyclohexanedione is disclosed in 
U.S. Pat. No. 5,006,158 to Carter et al; and 
2-(2'-nitro-4'-methylsulfonyloxybenzoyl-1,3-cyclohexanedione is disclosed 
in U.S. Pat. No. 5,089,046 to Lee et al. 
DESCRIPTION OF THE INVENTION 
In one aspect, the present invention is directed to a synergistic 
herbicidal composition comprising (a) 
2-(2'-nitro-4'-methylsulfonylbenzoyl)-1,3-cyclohexanedione ("NMSC") or 
2-(2'-nitro-4'-methylsulfonyloxybenzoyl)-1,3-cyclohexanedione ("NMSOC"); 
and (b) 2-chloro-4-ethylamino-6-isopropylamino-S-triazine. 
In another aspect, this invention is directed to a method of controlling 
undesirable vegetation applying to the locus of such vegetation a 
synergistic composition comprising (a) 
2-(2'-nitro-4'-methylsulfonylbenzoyl)-1,3-cyclohexanedione or 
2-(2'-nitro-4'-methylsulfonyloxybenzoyl)-1,3-cyclohexanedione; and (b) 
2-chloro-4-ethylamino-6-isopropylamino-S-triazine. 
The terms "synergism" and synergistic" are used herein to convey the result 
observed when a combination of herbicides demonstrates a potency in excess 
of that which the combination would be expected to produce based upon the 
potencies of each herbicide applied separately. 
The term "herbicide" is used herein to denote a compound which controls or 
modifies the growth of plants. The term "herbicidally effective amount" is 
used to indicate the quantity of such a compound or combination of such 
compounds which is capable of producing a controlling or modifying effect. 
Controlling or modifying effects include all deviations from natural 
development, for example: killing, retardation, leaf burn, albinism, 
dwarfing and the like. The term "plants" refers to all physical parts of a 
plant, including seeds, seedlings, saplings, roots, tubers, stems, stalks, 
foliage and fruits. 
In the compositions of this invention, the weight ratio of component (a) to 
component (b) at which the herbicidal response is synergistic, lies within 
the range of between about 1:50 and about 1:1, and is preferably between 
about 1:40 and about 4:5. 
Application rates will depend upon the particular plant species and degree 
of control desired. In general, the compositions of the invention are most 
efficiently employed at a rate of 0.001 to 5 pounds per acre (0.001 to 5 
kilograms per hectare). 
The compositions of this invention are useful as herbicides, demonstrating 
synergistic activity for the control of undesirable vegetation. The 
compositions can be formulated in the same manner in which herbicides are 
generally formulated. The compounds may be applied either separately or 
combined as part of a two-part herbicidal system. 
The object of the formulation is to apply the compositions to the locus 
where control is desired by a convenient method. The "locus" is intended 
to include soil, seeds, and seedlings, as well as established vegetation. 
The composition employed in the practice of the present invention can be 
applied in a variety of ways known to those skilled in the art, at various 
concentrations. The composition is useful in controlling the growth of 
undesirable vegetation by pre-emergence or post-emergence application to 
the locus where control is desired. In practice, the composition is 
applied as a formulation containing the various adjuvants and carriers 
known to or used in the industry for facilitating dispersion. The choice 
of formulation and mode of application for any given compound may affect 
its activity, and selection will be made accordingly. The compositions of 
the invention may thus be formulated as granules, as wettable powders, as 
emulsifiable concentrates, as powders or dusts, as flowables, as 
solutions, suspensions or emulsions, or in controlled-release forms such 
as microcapsules. These formulations may contain as little as about 0.5% 
to as much as amount 95% or more by weight of active ingredient. The 
optimum amount for any given compound will depend upon the nature of the 
seeds or plants to be controlled. 
Wettable powders are in the form of finely divided particles which disperse 
readily in water or other liquid carriers. The particles contain the 
active ingredient retained in a solid matrix. Typical solid matrices 
include fuller's earth, kaolin clays, silicas and other readily wet 
organic or inorganic solids. Wettable powders normally contain about 5% to 
about 95% of the active ingredient plus a small amount of wetting, 
dispersing, or emulsifying agent. 
Emulsifiable concentrates are homogeneous liquid compositions dispersible 
in water or other liquid, and may consist entirely of the active compound 
with a liquid or solid emulsifying agent, or may also contain a liquid 
carrier, such as xylene, heavy aromatic naphthas, isophorone and other 
non-volatile organic solvents. In use, these concentrates are dispersed in 
water or other liquid and normally applied as a spray to the area to be 
treated. The amount of active ingredient may range from about 0.5% to 
about 95% of the concentrate. 
Granular formulations include both extrudates and relatively coarse 
particles, and are usually applied without dilution to the area in which 
suppression of vegetation is desired. Typical carriers for granular 
formulations include sand, fuller's earth, attapulgite clay, bentonite 
clays, montmorillonite clay, vermiculite, perlite and other organic or 
inorganic materials which absorb or which can be coated with the active 
compound. Granular formulations normally contain about 5% to about 25% 
active ingredients which may include surface-active agents such as heavy 
aromatic naphthas, kerosene and other petroleum fractions, or vegetable 
oils; and/or stickers such as dextrins, glue or synthetic resins. 
Dusts are free-flowing admixtures of the active ingredient with finely 
divided solids such as talc, clays, flours and other organic and inorganic 
solids which act as dispersants and carriers. 
Microcapsules are typically droplets or granules of the active material 
enclosed in an inert porous shell which allows escape of the enclosed 
material to the surroundings at controlled rates. Encapsulated droplet are 
typically about 1 to 50 microns in diameter. The enclosed liquid typically 
constitutes about 50 to 95% of the weight of the capsule, and may include 
solvent in addition to the active compound. Encapsulated granules are 
generally porous granules with porous membranes sealing the granule pore 
openings, retaining the active species in liquid form inside the granule 
pores. Granules typically range from 1 millimeter to 1 centimeter, 
preferably 1 to 2 millimeters in diameter. Granules are formed by 
extrusion, agglomeration or prilling, or are naturally occurring. Examples 
of such materials are vermiculite, sintered clay, kaolin, attapulgite 
clay, sawdust and granular carbon. Shell or membrane materials include 
natural and synthetic rubbers, cellulosic materials, styrene-butadiene 
copolymers, polyacrylonitriles, polyacrylates, polyesters, polyamides, 
polyureas, polyurethanes and starch xanthates. 
Other useful formulations for herbicidal applications include simple 
solutions of the active ingredient in a solvent in which it is completely 
soluble at the desired concentration, such as acetone, alkylated 
naphthalenes, xylene and other organic solvents. Pressurized sprayers, 
wherein the active ingredient is dispersed in finely-divided form as a 
result of vaporization of a low boiling dispersant solvent carrier may 
also be used. 
Many of these formulations include wetting, dispersing or emulsifying 
agents. Examples are alkyl and alkylaryl sulfonates and sulfates and their 
salts; polyhydric alcohols; polyethoxylated alcohols; esters and fatty 
amines. These agents when used normally comprise from 0.1% to 15% by 
weight of the formulation. 
Each of the above formulations can be prepared as a package containing the 
herbicide together with other ingredients of the formulation (diluents, 
emulsifiers, surfactants etc.). The formulations can also be prepared by a 
tank mix method, in which the ingredients are obtained separately and 
combined at the grower site. 
These formulations can be applied to the areas where control is desired by 
conventional methods. Dust and liquid compositions, for example, can be 
applied by the use of power-dusters, boom and hand sprayers and spray 
dusters. The formulations can also be applied from airplanes as a dust or 
a spray or by rope wick applications. To modify or control growth of 
germinating seeds or emerging seedlings, dust and liquid formulations can 
be distributed in the soil to a depth of at least one-half inch below the 
soil surface or applied to the soil surface only, by spraying or 
sprinkling. The formulations can also be applied by addition to irrigation 
water. This permits penetration of the formulations into the soil together 
with the irrigation water. Dust compositions, granular compositions or 
liquid formulations applied to the surface of the soil can be distributed 
below the surface of the soil by conventional means such as discing, 
dragging or mixing operations.