SELECTIVE, BROADSPECTRUM WEED CONTROL IN SOYBEANS

Abstract: Less damage to soybeans occur when the combination of bentazon and a 3-substituted-pyridyl-oxy (or thio) phe­ noxy alkanoate herbicide is applied thereto, in comparison to the combination of bentazon and a 3-unsubstituted pyridy­ loxy (or thio) phenoxy alkanoate herbicide.

Description: SELECTIVE, BROADSPECTRUM WEED CONTROL IN SOYBEANS The present invention'relates to an improved method of selectively controlling grassy weeds and broadleaf weeds in soybean crops. 2-Pyridyloxy(or ;thio)phenoxy alkanoate grass herbicides are well known grass herbicides that are useful for selectively controlling annual and perennial grassy weeds in the presence of desirable broadleaf crops. Benzothiadiazinone derivatives are also well-known as herbicides and especially as broadleaf active herbicides. Pyridyloxytor thio)phenoxy alkanoate herbicides are typically applied post-emergently in the presence of nonionic surfactants. To extend the weed control spectrum in a.given application, it has been taught that pyridyloxy(or thio)phenoxy alkanoate herbicides be mixed with benzothiadiazinone broadleaf active herbicides and thereafter applied to unwanted vegetation to provide a broad spectrum herbicidal composition effective. against grasses and broadleaf weeds. See, for example, European Patent Application 4414 which teaches combinations of pyridyloxyphenoxy derivatives and other herbicides. In particular, European Patent Application 4414, teaches combining 2-(4-(2-pyridinyl)oxy)phenoxy propionate, n-butyl ester, i.e., commonly known as fluazifop-butyl herbicide, with bentazon and applying the combination to soybeans for selective broad spectrum weed control. A serious problem associated with the combination of fluazifop-butyl and bentazon when applied to soybean crops is an increase in phytotoxicity to the soybean plants. This is an especially annoying problem in view of the fact that the herbicidal activity to grasses of pyridyloxyphenoxy alkanoate herbicides is decreased when combined with benzothiadiazinone derivatives. In fact, technical literature distributed by the manufacturer of this herbicide acknowledges the phytotoxicity of the combination of fluazifop-butyl and bentazon towards soybeans and specifically recommends avoidance of the combination being applied to soybean crops. It has been found unexpectedly that pyridyloxy (or thio)phenoxy alkanoate grass herbicides that have a substituent other than hydrogen in the 3-position of the pyridine ring, when combined with benzothiadiazinone herbicides, exhibit less phytotoxicity or damage to soybean plants when the combination of herbicides is applied thereto, as compared to the combinations wherein the pyridyloxyphenoxy alkanoate herbicide contains hydrogen in the 3-position of the pyridine ring. In accordance with the present invention, pyridyloxy(or thio)phenoxy alkanoate herbicides having a substituent in the 3-position of the pyridine ring other than hydrogen, when combined with benzothiadiazinone herbicides, provide an effective broad spectrum herbicidal combination more selective to soybean plants than the above described herbicidal combination wherein the pyridyloxy(or thio)phenoxy alkanoate has hydrogen in the 3-position of the pyridine ring. Suitable substituents that can replace hydrogen in the 3-position of the pyridine ring include Cl, F, Br, I, CF3, C1-C4 alkyl, C1-C4 alkoxy and NO2. Of particular interest is the combination of bentazon with 2-(4-(3-chloro-5-(trifluoromethyl )-2- -pyridyl)oxy)phenoxy propionic acid and agriculturally acceptable salts, amides, alcohols, esters including reverse esters and ethers thereof. Also of interest is the combination of.bentazon with 2-(4-(3-fluoro-5 -(trifluoromethyl)-2-pyridyl)oxy)phenoxy propionic acid and agriculturally acceptable salts, amides, alcohols, esters and ethers thereof. Agriculturally acceptable derivatives of the acids are those salts, amides, alcohols, esters including reverse esters and ethers which possess herbicidal activity while being substantially non-phytotoxic to soybean plants. These herbicidal combinations provide broad spectrum weed control in soybean crops while exhibiting less phytotoxicity toward the soybean plants than the combination of bentazon and fluazifop-butyl, a pyridyloxyphenoxy propanoic acid ester having hydrogen as the substituent in the 3-position of the pyridine ring. Preferred pyridyloxy-phenoxy alkanoate herbicides include pyridyloxy-phenoxy propionate compounds of the formula EMI4.1 wherein X represents Cl, F, Br, I, C1-C4 alkyl, C1-C4 alkoxy, NO2 or -CF3; Y represents Cl, F, Br, I, C1-C4 alkyl; C1-C4 alkoxy, N02 or -CF3; and agriculturally acceptable salts, esters, alcohols, amides or ethers thereof Agriculturally acceptable salts, amides, alcohols, ethers and esters of the above pyridyloxy -phenoxy propionates include, for example, compounds of the formula EMI4.2 wherein X and Y are as hereinbefore defined; Z represents -CO2H, -CO2M, -CO2R, -COSR, -CONR'2, -CSNH2, -CN, -CH2OR' or -CH2O2CR'; M represents Na, K, Mg, Ca or R represents C1-C8 alkyl or C3-C6 alkoxyalkyl; each R' independently represents H or cl-C4 alkyl; and R" independently represents H, C1-C4 alkyl or C2-C3 hydroxyalkyl. Specific pyridinyloxyphenoxy propionate herbicides within the scope of the present invention include, for example: 2-(4-(3-chloro-5-(trifluoromethyl )pyridyl )- oxy)phenoxy propionic acid and agriculturally acceptable salts, alcohols, esters, amides and ethers thereof; 2-(4-(3-fluoro-5-(trifluoromethyl)pyridyl)- oxy)phenoxy propionic acid and agriculturally acceptable salts, alcohols, esters, amides and ethers thereof; methyl 2-(4-((3-chloro-5-(trifluoromethyl)-2 -pyridinyl)oxy)phenoxy)propionate; butyl 2-(4-((3-chloro-5-(trifluoromethyl)-2- -pyridinyl)oxy)phenoxy)propionate; ethoxy ethyl 2-(4-((3-chloro-5-(trifluoro methyl )-2-pyridinyloxy)phenoxy)propionate; ; and l-methoxy-2-propyl 2-(4-((3-chloro-5-(tri- fluoromethyl)-2-pyridinyl)oxy)phenoxy propionate; methyl 2-(4-((3-fluoro-5-(trifluoromethyl)-2 -pyridinyl)oxy)phenoxy)propionate; butyl 2-(4-((3-fluoro-5-(trifluoromethyl)-2- -pyridinyl)oxy)phenoxy)propionate; ethoxy ethyl 2-(4-((3-fluoro-5-(trifluoro methyl)-2-pyridinyl)oxy)phenoxy)propionate; and l-methoxy-2-propyl 2-(4-((3-fluoro-5-(tri- fluoromethyl)-2-pyridinyl)oxy)phenoxy)propionate. Preferred benzothiadiazinone herbicides include, for example, those of the formula: EMI5.1 wherein X represents hydrogen, chloro, bromo, fluoro, C1-C8 alkyl and nitro, and salts thereof. Specifically preferred benzothiadiazinone herbicides include, for example: 8-chloro-3-(1-methylethyl)-1H-2,1,3-benzothia diazin-4(3H)-one-2,2-dioxide; 8-nitro-3-(1-methylethyl)-1H-2,1,3-benzothia diazin-4(3H)-one-2,2-dioxide; 8-fluoro-3-(1-methylethyl)-1H-2,1,3-benzothia diazin-4(3H)-one-2,2-dioxide; 8-methyl-3-(1-methylethyl)-1H-2,1,3-benzothia diazin-4(3H)-one-2,2-dioxide; and 3-(1-methylethyl)-1H-2,1,3-benzothiadiazinone 4(3H)-one-2,2-dioxide, commonly known as bentazon. Bentazon, a broadleaf active herbicide and a preferred compound, is a commercially available product sold. under the trade name BASAGRAN. In the practice of the present invention the pyridyloxy-phenoxy alkanoate herbicide and the benzothiadiazinone herbicide are formulated into a spray formulation using well known techniques. For example, bentazon, formulated as the water-soluble Na salt, is mixed in water and thereafter 2-(4-(3 -chloro-5- (trifluoromethyl ) -2-pyridyl ) oxy)phenoxy propionic acid or an ester thereof, such as the methyl, butyl or ethoxy ethyl ester, is added to the bentazon solution, with agitation, so that a uniform mixture is formed containing both herbicides. .Once prepared the compositions of the present invention are applied to soybean crops employing procedures well known in the art. In one embodiment of the present invention, the Na salt of bentazon is combined with an ester or salt of 2-(4-(3-fluoro-5-(trifluoromethyl)-2-pyridyl)- oxy)phenoxy propionic acid in an aqueous spray mixture and applied to soybeans for broad spectrum weed control. In a preferred embodiment of the present invention, the Na+ salt of bentazon and an ester of 2-(4 -(3-chloro-5-(trifluoromethyl)-2-pyridyl)oxy)phenoxy propionic acid, formulated as an emulsifiable concentrate, are combined in an aqueous spray mixture in the presence of a surface active agent to facilitate leaf wetting and applied to soybeans for broad spectrum weed control. The exact amount of herbicide applied will vary, depending on many factors, such as, for example, the particular herbicides employed, soil conditions, vegetative conditions, climatological conditions to name a few, and is readily determinable by one skilled in the art. when bentazon, employed as the benzothiadiazinone herbicide, is combined with an ester of 2-(4-(3-chloro-5-(trifluoromethyl)-2-pyridyl)oxy)phenoxy propanoic acid, employed as the pyridyloxyphenoxy herbicide, the bentazon is used in amounts to provide from 0.5 to 1.5 lbs/acre (0.56 to 1.68 kgs/ha) and the ester of 2-(4-(3-chloro)-5-(trifluoromethyl)-2-pyridyl)oxy)phenoxy propanoic acid is present in amounts to provide from 0.03 to 0.5 lbs/acre (0.034 to 0.56 kgs/ha). The following examples further illustrate the practice of the present invention. Example 1 Various concentrations of fluazifop-butyl (formulated as a 2 lb/gal (0.24 kg/L) emulsifiable concentrate) and bentazon were combined in an aqueous tank mixture which included ORTHO X-77 (0.25% vZv) brand surfactant. The combination was applied in the field to Giant Foxtail (growth stage: 4-6 leaf; 7.6-12.7 cms in height) and soybeans (growth stage: 3 trifoliate, 8 inches (20 cms) in height) and evaluated 1 and 2 weeks after treatment for percent control of Giant Foxtail and percent damage to soybeans. Results are listed in Table 1. TABLE 1 Kg Active Ingredient % Giant Foxtail Control % Damage to Soybeans Run &num; per hectare (Weeks After Treatment) (Weeks After Treatment) 1 2 1 2 1. fluazifop-butyl..0.14 Kg/ha 68 86 0 0 2. fluazifop-butyl..0.14 65 45 30 17 bentazom.........0.84 3. fluazifop-butyl..0.28 73 89 2 5 4. fluazifop-butyl..0.28 67 70 30 17 bentazom.........0.84 5. fluazifop-butyl..0.56 75 88 10 6 6. fluazifop-butyl..0.56 8 95 40 29 bentazom.........0.84 Example 2 Various concentrations of 2-(4-(3-chloro-5 -(trifluoromethyl)-2-pyridinyl)oxy)phenoxy propionate, n-butyl ester (hereinafter "Cpd A") with bentazon were formulated and applied in the field as described in Example 1. The combination was applied in tank mixture to Giant Foxtail (3-6 leaf) and soybeans (1-2 trifoliates) and evaluated 1 and 2 weeks after treatment for percent control of Giant Foxtail and percent damage to soybeans. Results are listed in Table 2. Example 3 Various concentrations of fluazifop-butyl formulated as an emulsifiable concentrate (0.24 kg/L) with BASAGRANE brand bentazon and 2-(4-(3-chloro-5-(tri- fluoromethyl )-2-pyridinyl ) oxy)phenoxy propionic acid, n-butyl ester (hereinafter "Cpd A") with BASAGRAN brand. bentazon were applied as aqueous mixtures in the presence of ATPLUS 411F brand crop oil with emulsifiers to greenhouse grown soybeans. The soybeans were in the second (2nod9 trifoliate leaf stage at the time of treatment and evaluated for injury 4 days after treatment. Results are listed in Table 3. TABLE 2 Percent Percent Kg active control Giant damage to ingredient Foxtail (weeks soybeans (weeks Run &num; per hectare after treatment) after treatment) 1 2 3 4 1 Cpd. A 0.14 Kg/ha 93 98 0 0 2 Cpd. A 0.14 Kg/ha 95 96 15 0 bentazon 0.84 Kg/ha 3 Cpd. A 0.28 Kg/ha 95 99 0 0 4 Cpd. A 0.28 Kg/ha 99 100 8 0 bentazon 0.84 Kg/ha TABLE 3 Amount of active Average % ingredients in kg/ha injury to soybeans 0.84 kg bentazon (alone) 6.7 0.84 kg bentazon; 0.14 kg fluazifop-butyl 18.3 0.84 kg bentazon; 0.28 kg fluazifop-butyl 35 0.84 kg bentazon; 0.56 kg fluazifop-butyl 50 0.84 kg bentazon; 0.14 kg Cpd. A 10 0.84 kg bentazon; 0.28 lb Cpd. A 15 0.84 kg bentazon; 0.56 kg Cpd. A 30 1.68 kg bentazon (Alone) 16.6 1.68 kg bentazon; 0.14 fluazifop-butyl 42 1.68;keg bentazon; 0.28 fluazifop-butyl 60 1.68 kg bentazon; 0.56 fluazifop-butyl 78 1.68 kg bentazon; 0.14 Cpd. A 22 1.68 kg bentazon; 0.28 Cpd. A 25 1.68 kg bentazon; 0.56 Cpd. A 40 Example 4 Substantially the same procedures as those described in Examples 1-3 were repeated except that 0.25% v/v ORTHO X-77 brand surfactant was used as the surfactant. Additionally, 2-(4-(3-fluoro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy propionic acid, methyl ester (hereinafter "Cpd. B") with BASAGRAN brand bentazon was applied to soybeans and evaluated for phytotoxicity toward soybean plants 6 days after treatment. Results are listed in Table 4. TABLE 4 Amount of active Average % ingredients in kg/ha injury to soybeans 0.84 kg bentazon (alone) 10 0.84 kg bentazon; 0.14 kg fluazifop-butyl 15 0.84 kg bentazon; 0.28 kg fluazifop-butyl 25 0.84 kg bentazon; 0.56 kg fluazifop-butyl 50 0.84 kg bentazon; (Alone) 10 0.84 kg bentazon; 0.14 kg Cpd. A 15 0.84 kg bentazon; 0.28 kg Cpd. A 15 0.84 kg bentazon; 0.56 kg Cpd. A 20 0.84 kg bentazon; (Alone) 10 0.84. kg bentazon; 0.14 kg Cpd. B 15 0.84.kg bentazon; 0.28 kg Cpd. B 20 0.84 kg bentazon; 0.56 kg Cpd. B 20 1.68 kg bentazon; (Alone) ¯ 15 1.68 kg bentazon; 0.14 fluazifop-butyl 30 1.68 kg bentazon; 0.28 fluazifop-butyl 45 1.68 lb bentazon; 0.56 fluazifop-butyl 55 1.68 kg bentazon; (Aione) 15 1.68 kg bentazon; 0.14 Cpd. A 20 1.68 kg bentazon; 0.28 Cpd. A 25 1.68 kg bentazon; 0.56 Cpd. A 35 1.68 kg bentazon; (Alone) 15 1.68 kg bentazon; 0.14 Cpd. B 20 1.68 kg.bentazon; 0.28 Cpd. B 25 1.68 kg bentazon; 0.56 Cpd. B 40 On repeating the procedures described in the above examples employing a combination of benzothiadiazinone herbicides and pyridyloxyphenoxy alkanoate herbicides containing a substituent other than hydrogen in the 3-position of the pyridine ring, substantially the same results are obtained, i.e., less damage to soybean plants when compared to the combination of benzothiadiazinones and pyridyloxyphenoxy alkanoates having hydrogen as the sub-stituent in the 3-position of the pyridine ring. In further embodiments, the broad spectrum herbicidal compositions of the present invention can be advantageously employed in combination with one or more additional pesticidal compounds. Such additional pesticidal compounds may be insecticides, nematocides, arthropodicides, herbicides, fungicides or bactericides that are compatible with the compositions of-the present invention and non-phytotoxic to soybeans when applied thereto. Accordingly, in such embodiments, the additional pesticidal compounds are employed as supplemental toxicants for the same or for different pesticidal uses, or as additaments.

Claims: CLAIMS: 1. A method of selectively controlling broadleaf weeds and grassy weeds in a soybean crop by application of a combination of a pyridyloxy(or thio)-phenoxy alkanoate grass herbicide and a benzothiadiazinone broadleaf weed herbicide, which comprises employing a pyridyloxy(or thio)phenoxy alkanoate grass herbicide having in the 3position of the pyridine ring a substituent other than a hydrogen atom. 2. A method as claimed in claim 1 wherein the pyridyloxy(or thio)phenoxy alkanoate grass herbicide is a pyridyloxyphenoxy propionate having a chlorine or fluorine atom as the substituent in the 3-position of the pyridine ring. 3. A method as claimed in claim 2 wherein the pyridyloxyphenoxy propionate grass herbicide is 2-(4-(3chloro-5-(trifluoromethyl)-2-pyridinyl)oxy)-phenoxy propionic acid or an agriculturally acceptable salt, alcohol, ester amide or ether thereof. 4. A method as claimed in claim 3 wherein the pyridyloxyphenoxy propionate grass herbicide is a butyl, methyl or ethoxyethyl ester of 2-(4-(3-chloro-5-(tri fluoromethyl) -2-pyridinyl)--oxy) phenoxy propionic acid. 5. A method as claimed in claim 2 wherein the pyridyloxyphenoxy propionate grass herbicide is 2-(4-(3fluoro-5-(trifluoromethyl)-2-pyridinyl)oxy)-phenoxy propionic acid or an agriculturally acceptable salt, alcohol, ester, amide or ether thereof. 6. A method as claimed in claim 5 wherein the pyridyloxyphenoxy propionate grass herbicide is a butyl, methyl or ethoxyethyl ester of 2-(4-(3-fluoro-5-(trifluoromethyl)-2-pyridinyl)oxy)phenoxy propionic acid. 7. A method as claimed in any one of the preceding claims wherein the benzothiadiazinone herbicide is 3-(1-methylethyl)-1H-2,1,3-benzothiadiazinone-4(3H)-one- 2,2-dioxide. 8. A method as claimed in claim 7 wherein the said benzothiadiazinone-herbicide is used in combination with an ester of 2-(4-(3-chloro-5-(trifluoromethyl)-2pyridyl)oxy)-phenoxy propionic acid as the pyridyloxyphenoxy herbicide. 9. A method as claimed in claim 8 wherein the benzothiadiazinone herbicide is used in an amount to provide 0.56 to 1.68 kgs/ha and the pyridyloxyphenoxy herbicide is used in an amount to provide 0.034 to 0.56 kgs/ha.

Inventors: GERWICK III, B. CLIFFORD
Applicants: THE DOW CHEMICAL COMPANY
Application year: 1983
Main classification: A01N43
IPC codes: A01N43