NO861338L - SYNERGISTIC HERBICIDE MIXTURES. - Google Patents

Description

Protection of crops against grass species and other vegetation that inhibits crop growth is an ever-recurring problem in agriculture. To help combat this problem, scientists in the field of synthetic chemistry have produced a variety of chemicals and chemical formulations that act to control such unwanted growth. Chemical herbicides of many types are described in the literature and a large number are in practical use.

In some cases, herbicides have been shown to be more effective in combination than when they are used individually. The result is often called "synergism", as the combination shows a strength or a level of activity that exceeds what it would be expected to have based on knowledge of the individual strengths of the components. The present invention is based on the discovery that certain thiol carbamates and certain substituted diphenyl ether compounds, which are already individually known to be herbicidally active, show this synergism when they are used in combination.

The two classes of compounds which make up the compositions which are the subject of the present invention are known for their effects on plant growth independently.

Thiol carbamates are described as herbicides in US patents 3,185,720 (Tilles et al., 25 May 1965), 3,198,786 (Tilles et al., 3 August 1965) and 2,913,327 (Tilles et al., 17 November .1959).

The diphenyl ether compounds which make up the second class of compounds in the mixture according to the present invention are a varied group, but are all now available for purchase from different manufacturers as will be seen here.

It has now been discovered that synergism in controlling unwanted growth is shown by mixtures comprising a mixture of the following two ingredients:

(a) a herbicidally effective amount of a thiol carbamate of the formula

in which

X is hydrogen, chlorine or bromine; and

R<1> and R<2> are individually selected from the group C1-C6alkyl and C5-C-cycloalkyl, and (b) a herbicidally effective amount of a substituted diphenyl ether compound selected from the group sodium 5[2-chloro-4- (trifluoromethyl)phenoxy]-2-nitrobenzoate, methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate, methyl 2-[2,4-(dichlorophenoxy)phenoxy]-propanoate, 2-chloro-2-{3 -ethoxy-4-nitrophenoxy)-4-trifluoromethyl)benzene, 5-^2-chloro-4-(trifluoromethyl)-phenoxyj-N-(methylsulfonyl)-2-nitrobenzamide, 4-nitrophenol-a,a,a -trifluoro-2-nitro-p-tolyl ether, 2,4-dichlorophenyl-3-methoxy-4-nitrophenyl ether and 2,4-dichlorophenyl-p-nitrophenyl ether.

The term "alkyl" is used herein to denote both straight chain and branched groups. Examples of alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, etc. All carbon atom ranges include the upper and lower limits.

Examples of thiol carbamates that can be used in the present invention are:

1. S-benzyl dipropyl thiol carbamate

2. S-benzyl-ethyl, 1,2-dimethylpropylthiocarbamate

3. S - (2-chlorobenzyl)-N,N-diethylthiocarbamate

4. S - (4-chlorobenzyl)-N,N-diethylthiolcarbamate

These and other thiol carbamates within the scope of the invention can be produced by the method described in US patents no. 2,913,327, 3,185,720 and 3,198,786 mentioned above and US patents no. 3,144,475, 2,992,091 and 3,207,775.

The preferred thiol carbamate for use in the invention is S-benzyl dipropyl thiol carbamate.

The preferred diphenyl ether for use in the composition according to the invention is 2,4-dichlorophenyl-p-nitrophenyl ether.

Each of the other compounds listed in subsection (b) may be purchased.

The terms "synergism" and "synergistic" are used here for the result seen when a combination of herbicides shows a strength beyond what the combination could be expected to give based on the strengths when each herbicide is applied separately.

The term "herbicide" is used herein to denote a compound that controls or modifies the growth of plants. The term "herbicidally effective amount" is used to indicate the amount of such compound or combination of such compounds, which is capable of producing a controlling or modifying effect. Controlling or modifying effects are all deviations from natural development, for example: emission, retardation, leaf burning, dwarfing and the like. The term "plants" is used here to include all post-emergence vegetation from sprouts to established growth.

In the mixture according to the invention, the thiol carbamate: diphenyl ether weight ratio at which the herbicidal reaction is synergistic is between the range of approx. 0.125:1 to approx. 8:1. The synergism is observed especially when the mixture is used against Fumaria officinalis, Galium aparium and P apaver spp.

The application quantities will depend on the grass species to be controlled and the desired degree of control. In general, the compositions according to the present invention are most effective when used in an amount of 0.011 to 56 kg per hectare of the active ingredients, preferably 0.11 to 28 kg per hectares.

The mixtures are particularly effective in controlling grass species that grow in sugar beet and small grain crops such as wheat, barley and oilseed rape.

EXAMPLE 1

Synergism in grass species control using S-benzyl thiocarbamates and nitofen.

The herbicidal reactions from a combined use of S-benzyl-dipropylthiolcarbamate (compound 1) and nitrofen (compound 2) were studied by means of a greenhouse experiment. Nitrofen is:

2,4-dichlorophenyl-p-nitrophenyl ether.

Aluminum boxes (flower boxes) measuring 19 x 8 x 6 cm were filled with a loamy sandy soil and six furrows were impressed across the width of each flower box. The following plant species were sown in the furrows:

Chemical solutions sprayed on the same day as sowing were prepared as follows: Water was used to dilute both compound 1 (80% emulsifiable concentrate) and compound 2 (25% emulsifiable concentrate). The chemical solutions were brought to the soil surface for pre-emergence application using a linear spray table. The table was calibrated to a spray volume of 235 liters per hectares. Each compound was applied individually in the following application rates:

Compound 1 was used in all possible application rate combinations with compound 2. Each experiment was arranged as a 5 x 5 matrix (containing zero application rate) and performed as a statistically complete block with two replications.

Flat planters were placed in a shaded greenhouse after spraying and watered by showering from above. Air temperatures ranged from 15°C to 17°C. The flat planters were kept moist during each experiment.

Nineteen days after treatment, each row of sprouts was scored visually for growth control due to all injury factors. Untreated planters with sprouts were used for comparison. Zero percent damage or growth control is equivalent to growth in the control boxes. One hundred percent growth control is equivalent to complete extermination.

Herbicidal synergistic reactions were measured using Limpel<1>'s formula (Limpel, L.E. et al., 1962, "Weed Control by Dimethyl-tetrachloroterephthalate Alone and in Certain Combinations," Proc. NEWCC, 16:48-53) :

where E = expected reaction (E)

where X = observed (0) value of percent growth control when the first herbicide is applied alone; and

where Y = observed (0) value for growth control when the second herbicide is applied alone.

The reaction or synergy (R) from a combined herbicide treatment is synergistic (S) when an observed value is greater than an expected value. A synergistic reaction is one in which the cooperative reaction is greater than the sum of the reactions from the individual chemical treatments. An antagonistic reaction (Å) is the opposite situation. A reaction is additive (AD) when the observed and expected reaction are equal.

The following table shows the average data and results for the experiment. It can be concluded that combined applications of compound 1 with compound 2 lead to lasting synergistic herbicidal reactions.

The mixtures according to the present invention show synergistic activity as herbicides in the control of unwanted growth when they are applied to such vegetation before or after growth. The mixtures are generally available as formulations containing inert or occasionally active components or dilution carriers in addition to the active compounds. Examples of such components or carriers are water, organic solvents, surfactants, oil, water-in-oil emulsions, wetting agents, dispersing agents and emulsifying agents. The herbicidal formulations generally take the form of wettable powders, solutions or emulsifiable concentrates.

Wettable powders are finely divided mixtures that comprise a particulate carrier impregnated with the herbicidal compound and additionally contain one or more surfactants. The surfactants provide rapid dispersion of the powder in an aqueous medium and provide stable, sprayable suspensions. A wide variety of surfactants can be used, e.g. long-chain fatty alcohols and alkali metal salts of the sulfated fatty alcohols; salts of sulfonic acid; esters of long-chain fatty acids; and polyhydroxy alcohols, in which the alcohol groups are free, omega-substituted polyethylene glycols of relatively long chain length.

The herbicidal mixtures can also be applied to the foliage in the form of a solution in a suitable solvent. The solvents commonly used in herbicidal formulations are paraffin, fuel oil, xylene, petroleum fractions with boiling ranges above xylene, and aromatic petroleum fractions rich in methylated naphthalenes.

The most preferred formulations are emulsifiable concentrates consisting of an oil solution of the herbicide together with an emulsifier. Before use, the concentrate is diluted with water to a slurried emulsion of oil droplets. The emulsifiers used are normally a mixture of anionic and non-ionic surfactants. Other additives such as dispersants and adhesives can be included in the emulsifiable concentrate.

The formulations described above can be applied to the vegetation you want to control in all the usual ways, either before or after the vegetation has sprung up from the ground. The vegetation can be at any stage of development after growth from sprouts to fully grown plants. Application can be achieved by all common techniques such as the use of ground spraying equipment or airborne sprayers. Various other techniques will be apparent to one skilled in the pesticide art.

Claims (10)

1. Synergistic herbicide mixture, characterized in that it consists of a mixture of (a) a herbicidally effective amount of a thiol carbamate with the formula in which X is hydrogen, chlorine or bromine; and R<1> and R<2> are independently selected from the group C1-C6 alkyl and C8-C7 cycloalkyl, and (b) a herbicidally effective amount of a substituted diphenyl ether compound selected from the group sodium 5-[.2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoate, methyl 5-(2,4-dichlorophenoxy) -2-nitrobenzoate, methyl 2-[2,4-(dichlorophenoxy)phenoxy-propanoate, 2-chloro-2-(3-ethoxy-4-nitrophenoxy)-4-trifluoromethyl)benzene, 5-£2-chloro-4 -(trifluoromethyl)-phenoxy-N-(methylsulfonyl)-2-nitrobenz-amide, 4-nitrophenol-a,a,a-trifluoro-2-nitro-p-tolyl ether, 2,4-dichlorophenyl-3-methoxy-4 -nitrophenyl ether and 2,4-dichlorophenyl-p-nitrophenyl ether in a weight ratio of (a) to (b) from approx. 0.125:1 to approx. 8:1. 2. Mixture according to claim 1, characterized in that (a) is S-benzyl-dipropylthiocarbamate and (b) is 2,4-dichlorophenyl-p-nitrophenyl ether. 3. Mixture according to claim 1, characterized in that (a) is S-benzylethyl, 1,2-dimethylpropyl thiolcarbamate and (b) is 2,4-dichlorophenyl-p-nitrophenyl ether. 4. Mixture according to claim 1, characterized in that (a) is S-(2-chlorobenzyl)-N,N-diethyl-thiocarbamate and (b) is 2,4-dichlorophenyl-p-nitrophenyl ether. 5. Method for controlling unwanted growth, characterized by applying to the vegetation a herbicidal mixture comprising a mixture of (a) a herbicidally effective amount of a thiolcarbamate with the formula in which X is hydrogen, chlorine or bromine; and R <1> and R <2> independently are selected from the group Ci-Ce alkyl and Cs-C7 cycloalkyl, and (b) a herbicidally effective amount of a substituted diphenyl ether compound selected from the group consisting of sodium 5-C2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoate, methyl 5-(2,4-dichlorophenoxy)-2- nitrobenzoate, methyl 2-[ 2, 4-(dichlorophenoxy)phenoxy-propanoate, 2-chloro-2-(3-ethoxy-4-nitrophenoxy)-4-trifluoromethyl)benzene, 5-f2-chloro-4-(trifluoromethyl) -phenoxy-N-(methylsulfonyl)-2-nitrobenz-amide, 4-nitroenol-oc, a , a-trifluoro-2-nitro-p-tolyl ether , 2,4-dichlorophenyl-3-methoxy-4-nitrophenyl ether and 2,4-dichlorophenyl-p-nitroph enyl ether. 6. Method according to claim 5, characterized by (a) using S-benzyl-dipropylthiocarbamate and (b) 2,4-dichlorophenyl-p-nitrophenyl ether. 7. Method according to claim 5, characterized in that as (a) S-benzylethyl, 1,2-dimethylpropyl thiolcarbamate is used and as (b) 2,4-dichlorophenyl-p-nitrophenyl ether. 8. Method according to claim 5, characterized in that as (a) one uses S-(2-chlorobenzyl)-N,N-diethyl-thiocarbamate and as (b) 2,4-dichlorophenyl-p-nitroph enyl ether. 9. Method for controlling unwanted growth, characterized by applying to the vegetation before or after growth a herbicidal mixture comprising a mixture of (a) a herbicidally effective amount of a thiolcarbamate with the formula in which X is hydrogen, chlorine or bromine; and R<1> and R<2> are independently selected from the group Ci-Ce alkyl and Cs-C7 cycloalkyl, and (b) a herbicidally effective amount of 5-[2-chloro-4(trifluoromethyl)phenoxy]-2-nitrobenzoate in a weight ratio of (a) to (b) from about 0.125:1 to approx. 8:1. 10. Procedure for control of grass species selected from Beta vulgaris, Fumaria officinalis, Bapavar ssp. or Metricaria recutita, characterized by applying to the grass species before or after growth a herbicide mixture comprising a mixture of (a) S-benzyldipropyl-thiocarbamate and (b) 2,4-dichlorophenyl-p-nitrophenyl ether in a weight ratio of (a) to (b) from about. 8:1 to 1:1.