A HERBICIDAL COMPOSITION AND METHOD FOR CONTROLLING THE GROWTH OF PLANTS

Abstract: A herbicidal composition which comprises a synergistic mixture of active ingredients (A) and (B); ingredient (A) being 4-amino-3,5-dichloro-6-fluoro-2-pyridinyl acetic acid or a derivative thereof and ingredient (B) being 3,5-dibromo-4-­ hydroxy benzonitrile or a derivative thereof.

Description: A HERBICIDAL COMPOSITION AND METHOD FOR CONTROLLING THE GROWTH OF PLANTS The present invention relates to herbicidal comr:ositions and to methods for the control of weeds. Both 4-amino-3, 5-dichloro-6-fluoro-2-pyridinyl acetic acid and 3,5-dibromo-4-hydroxy benzonitrile (bromoxyniyl) are known herbicides which may be used in the free form, or in the form of salts or esters thereof. Hereinafter the term "derivatives" will be used to designate the esters or salts of the above-mentioned herbicides. Salt and ester derivatives included herein are those which are commonly used. For example, salts include the alkaii metal salts such as the sodium or potassium salts and salts with amines, such as ethanolamine. Esters that may be employed include alkyl esters (C112), phenylalkyl (C7¯10) and alkoxyalkyl (C212). It has now been found that a combination of 4-amino-3,5-dichloro-6-fluoro-2-pyridinyl acetic acid and 3,5-dibrorno-4-hydroxy benzonitrile, or derivatives thereof, in certain proportions have unexpected properties in the control of broad-leafed weeds. The degree of control constitutes a synergistic effect. According to the present invention there is provided a herbicidal composition which comprises a synergistic mixture of active ingredients (A) and (B); ingredient (A) being 4-am no-3,5-dichloro-6-fluoro-2-pyridinyl acetic acid or a derivative thereof (as hereinbefore defined) and ingredient (B) being 3,5-dibromo-4-hydroxy benzonitrile or a derivative thereof (as hereinbefore defined) Ingredient A is preferably in the form of the l-methyl heptyl ester while B is preferably in the form of the octanoate ester. Whether or not a particular mixture of active ingredients A and 3 is a synergistic mixture in accordance with this invention may be determined by the follovins test: Three separately growing samples of Veronica persica (Buxbals speedwell) at the 4 to 10 leaf growth stage are sprayed, one with p g/ha of 4-amino-3,5-dichloro6-fluoro-2 pidinyl acetic acid, or a derivative thereof, another with q g/ha of 3,5-dibromo-4-hydroxy benzonitrile, or a derivative thereof, and the third with the mixture under test to give a dose rate of p g/ha of A and q g/ha of B. After a period of 28 days if the plants are grown in a green house or six to twelve weeks if grown in the field, the plants are inspected to determine what inhibition of growth has occurred. The results are treated in a manner shown in the article "Calculating Synergistic and Antagonistic Responses of Herbicide Combinations" by S.R. Colby (Weeds 1967 50 p. 20-22). By this method an expected result E for the use of the mixture is calculated and compared with the observed result. If X = percent inhibition of growth with herbicide (a) at p g/ha and Y = percent inhibition of growth with herbicide (b) at q g/ha then E = expected percent inhibition of growth with herbicides (a) + (b) at p+q g/ha is equal to X+Y - XY. 100 If the observed inhibition of growth (O) is 10% or more greater than the calculated expected figure E, (lOOx(O-E)/ElO) then the mixture is synergistic as the term is used in this specification. In general, a synergistic effect is observed with compositions which contain A and B in a weight ratio of from 1:10 to 4:1, preferably from 1:5 to 2:1. The compositions of the present invention are particularly valuable for the selective control of weeds, particularly broad-leafed weeds, in cereal crops, such as wheat and in barley and in graminaceous crops generally. Since the compositions are selective, a co-potentiating or synergistic effect is not observed with respect to all kinds of plants. The compositions of the present invention have been found to be suitable for use in the general postemergent control of weeds or other unwanted vegetation. For such uses, compositions of the unmodified combinations of active ingredients of the present invention can be employed. However, the present invention embraces the use of the combinations of active ingredients with an inert carrier or a material known in the art as an adjuvant in solid or liquid form. Thus, for example, the active ingredients can be disposed on a finely divided solid and employed therein as a dust. The active ingredients, or a solid composition comprising the active ingredients may be dispersed in a suitable solvent, typically with the aid of a wetting agent, and the resulting suspension employed as a spray. Preferably the compositions of the present invention are employed in the form of wettable powders or emulsifiable concentrates. The concentration of the active ingredients in the compositions of the present invention is generally within the range of from 0.0001 to 95 percent by weight. In compositions to be employed as concentrates, the active ingredients are usually present in a concentration of from 1 to 80 percent by weight. The compositions may also contain other conventional additives, such as fertilizers, phytotoxicants, plant growth regulates, or pesticides. This invention also provides a method for controlling plant growth which comprises applying to plants or to soil a composition as defined hereinbefore. The rate of application providing the required degree of control will depend on the type of plant, stage of growth of plants and/or climatic conditions. Usually the composition is applied to provide from 50 g/ha to 200 g/ha of active ingredient (A) and from 50 g/ha to 500 g/ha of active ingredient (B). The preferred rate of application being from 75 g/ha to 200 g/ha of active ingredient (A) and from 1QO g/ha to 375 g/ha of active ingredient (B). A further embodiment of this invention provides a method for controlling plant growth which method comprises bringing together on the plants or soil 4-amino-3,5-dichloro-6-fluoro-2-pyridinyl acetic acid or a derivative thereof, and 3,5-dibromo-4-hydroxy benzonitrile, or a derivative thereof, in proportions to form a synergistic mixture as hereinbefore defined. The compositions of the present invention have been found suitable for post-emergent control of broadleafed weeds in particular Veronica persica (Buxbaum Speedwell), Stellaria media, (Chickweed), Viola arvensis (pansy), Polygonum lapathifolium(pale persicaria), Polygonum persicaria (red shank), Polygonum aviculare (knot grass), Polygonum convolvulus (black bindweed), Chenopodium album (fat hen), Calium aparine (cleavers), Myosotis arvensis (forget-me-not) and Lamium purpureum (red deadnettle). The following Examples further illustrate the present invention. EX¯4PLE 1 A field trial was carried out in which a plot infested with Veronica persica at the young plant stage was divided into rectangular areas which were sprayed at various application rates with aqueous solutions of (A) 4-amino-3,5-dichloro-6-fluoro-2-pyridinyl acetic acid and/or (B) 3,5-dibromo-4-hydroxy benzonitrile; (A) being present as the l-methyl heptyl ester and (B) as the octanoate ester. The degree of weed control was assessed 48 days after spraying. Application rates of compound (A) of 200 g/ha and below gave a poor control of Veronica persica. The same effect was obtained with compound (B) at application rates of 500 g/ha and below. However application of a solution containing both compounds at application rates of 100-200 g/ha for compound (A) and 100-500 g for compound (B) gave complete kill of Veronica persica. EXAMPLE Control of Veronica persica (Buxbaum-Speedwell) in spring barley in 1 field trial. EMI8.1 <tb> <SEP> OBSERVED <SEP> EXPECTED <tb> TREATMENT <SEP> RATE/HA <SEP> % <SEP> CONTROL <SEP> % <SEP> CONTROL <tb> <SEP> COMPOUND <SEP> A <SEP> 100 <SEP> 23 <tb> <SEP> 150 <SEP> 20 <tb> <SEP> 200 <SEP> 53 <tb> <SEP> COMPOUND <SEP> B <SEP> 100 <SEP> 42 <tb> <SEP> 200 <SEP> 38 <tb> <SEP> 300 <SEP> 45 <tb> <SEP> 400 <SEP> 63 <tb> <SEP> 500 <SEP> 65 <tb> <SEP> COMPOUND <SEP> A+B <SEP> 100+300 <SEP> 100 <SEP> 58 <tb> <SEP> 100+400 <SEP> 100 <SEP> 71 <tb> <SEP> 100+500 <SEP> 100 <SEP> 73 <tb> <SEP> 150+300 <SEP> 100 <SEP> 56 <tb> <SEP> .150+400 <SEP> 100 <SEP> 70 <tb> <SEP> 150+500 <SEP> 100 <SEP> 72 <tb> <SEP> 200+100 <SEP> 100 <SEP> 64 <tb> <SEP> 200+200 <SEP> 100 <SEP> 62 <tb> <SEP> 200+300 <SEP> 100 <SEP> 66 <tb> EXAMPLE 2 Two field trials were carried out in which plots infested with Polygonum aviculare at the young plant stage were divided into rectangular areas which were sprayed at various application rates with aqueous solutions of (A) and or (B), the compounds being present in solution as the l-methyl heptyl ester for (A) and the octanoate ester for (B). The degree of weed control was assessed 51 days after spraying. Application rates of compound (A) of 250 g/ha and below gave a poor control of Polygonum aviculare. The same effect was obtained with compound (B) at application rates of 500 g/ha and below. However application of a solution containing both compounds at application rates of 75 g/ha for compound (A) and 300 g/ha for compound (B) gave complete kill of all Polygonum aviculare plants present. Other combinations of compounds (A) and (B) also gave excellent weed control as demonstrated in this example. EXAMPLE 2 Control of Polygonum aviculare in springbarleyin 2 field trials EMI10.1 <tb> <SEP> MEAN <SEP> % <SEP> CONTROL <tb> TREATMENT <SEP> RATE/HA <SEP> OBSERVED <SEP> EXPECTED <SEP> <tb> COMPOUND <SEP> A <SEP> 75 <SEP> 40 <tb> <SEP> 100 <SEP> 46 <tb> <SEP> 150 <SEP> 53 <tb> <SEP> 200 <SEP> 42 <tb> <SEP> 250 <SEP> 53 <tb> COMPOUND <SEP> B <SEP> 200 <SEP> 38 <tb> <SEP> 300 <SEP> 42 <tb> <SEP> 400 <SEP> 40 <tb> <SEP> 500 <SEP> 40 <tb> COMPOUND <SEP> A+B <SEP> 75+300 <SEP> 100 <SEP> 67 <tb> <SEP> 75+400 <SEP> 100 <SEP> . <SEP> 64 <tb> <SEP> 75+500 <SEP> 100 <SEP> 64 <tb> <SEP> 1001200 <SEP> 100 <SEP> 66 <tb> <SEP> 100+300 <SEP> 100 <SEP> 69 <tb> <SEP> 100+450 <SEP> 85 <SEP> 68 <tb> <SEP> 100+500 <SEP> 100 <SEP> 68 <tb> <SEP> 150+300 <SEP> 100 <SEP> 73 <tb> <SEP> 150+400 <SEP> 100 <SEP> 71 <tb> <SEP> 150+500 <SEP> 100 <SEP> 72 <tb> <SEP> 200+300 <SEP> 95 <SEP> 66 <tb> <SEP> 200+400 <SEP> 96 <SEP> 65 <tb> <SEP> 200+500 <SEP> 100 <SEP> - <SEP> 65 <tb> <SEP> 250+500 <SEP> 100 <SEP> 71 <tb> 250+500 <SEP> 100 <SEP> 71 <tb> EXAMPLE 3 A formulation was prepared containing the following ingredients: : Acetic acid, (4-amino-3,5-dichloro-6-fluoro-2- g/litre pyridinyl-oxy-) ,1-methyl heptyl ester 288 3, 5-dibromo-4-hydroxy benzonitrile octanoate ester 524 Solvesso 100 158 Tensiofix 7938 25 Tensiofix 7953 25 The formulation was used at an application rate of 2.Otper hectare, after dilution with water to 200t, to control weeds in cereal crops. Crop areas of spring barley, spring wheat, winter barley and winter wheat were sprayed overall at growth stages between the 5 leaf stage and commencement of jointing. An excellent control of broad leaved weeds including Polygonum aviculare, Veronica persica, Galium aparine, Stellaria media, Myosotis arvensis, Polygonum convolvulus and Lamium purpureum.

Claims: CLAIMS: 1. A herbicidal composition which comprises a synergistic mixture of active ingredients (A) and (B); ingredient (A) being 4-amino-3,5-dichloro-6-fluoro-2pyridinyl acetic acid or a derivative thereof (as herenbefore defined) and ingredient (B) being 3,5 dibrrno-4-hydroxy benzonitrile or a derivative thereof (as hereinbefore defined). 2. A composition as claimed in claim 1 wherein ingredient (A) is in the form of the l-methyl heptyl ester 3. A coraposition as claimed in claim 1 or claim 2 wherein ingredient (B) is in the form of the octanoate esters. 4. A composition as claimed in any one of the precding claims wherein the active ingredients (A) and (B) a=re present in a weight ratio of from 1:10 to 4:1. 5. A composition as claimed in claim 4 wherein the active ingredients (A) and (B) are present in a weight ratio of from 1:5 to 2:1. 6. A composition as claimed in any one of the preceding claims which is in the form of a wettable powder. 7. A composition as claimed in any one of claims 1 to 5 which is in the form of an emulsifiable concentrate. 8. A composition as claimed in claim -l substantially as hereinbefore described in any one of the Examples. 9. A method for controlling the growth of plants which comprises applying to the plants or to the soil a composition as claimed in any one of claims 1 to 8. 10. A method as claimed in claim 9 wherein the composition is applied at a rate to provide from 50 g/ha to 200 g/ha of active ingredient (A) and from 50 g/ha to 500 g/ha of active ingredient (B). 11. A method as claimed in claim 10 wherein the composition is applied at a rate to provide from 75 g/ha to 200 g/ha of active ingredient (A) and from 100 g/ha to 375 g/ha of active ingredient (B). 12. A method as claimed in claim 9 substantially as hereinbefore described in any one of the Examples. 13. A method for controlling the growth of plants which comprises bringing together on the plants or soil (A) 4-amino-3, 5-dichloro-6-fluoro-2-pyridinyl acetic acid or a derivative thereof (as hereinbefore defined) and (B) 3,5-dibromo-4-hydroxy benzonitrile or a derivative thereof (as hereinbefore defined) to form a synergistic mixture. 14. A method as claimed in any one of claims 9 to 12 wherein the plant whose growth is controlled is a Broad Leafed weed. 15. A method as claimed in any one of claims 9 to 14 wherein the plant whose growth is controlled is present amongst cereal plants.

Inventors: BROWN, JOHN GRAHAM, 7, ALLEE DE L'ALKANAL, Brown, John Graham, 7, Allée de l'Alkanal
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1982
Main classification: A01N43
IPC codes: A01N43