Herbicidal mixtures

Details Herbicidal mixtures Herbicidal mixtures

1998-06-10

2001-05-29

Clardy, S. Mark (Department: 1616)

Plant protecting and regulating compositions

Antidotes

Hetero ring containing antidote

C504S105000, C504S134000, C504S136000

Reexamination Certificate

active

06239070

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a method of safening herbicidal 4-benzoylisoxazoles and 2-cyano-1,3-diones by sulfonylurea herbicides, and to compositions containing the same.
BACKGROUND OF THE INVENTION
It is known that many herbicides injure crop plants at herbicide application rates needed to control weed growth. This renders many herbicides unsuitable for controlling weeds in the presence of certain crops. Where weed growth in crops is uncontrolled however, this results in lower crop yield and reduced crop quality, as weeds will compete with crops for nutrients, light and water. Reduction in herbicidal injury to crops without an unacceptable reduction in the herbicidal action can be accomplished by use of crop protectants known as “safeners”, also sometimes referred to as “antidotes” or “antagonists”.
4-Benzoylisoxazoles are known to possess herbicidal properties, for example see European Patent Publication Nos. 0418175, 0487357, 0527036 and 0560482. European Patent Publication Nos. 0496630, 0496631, 0625505 and 0625508 disclose certain 1-phenyl-2-cyano-1,3-dione derivatives possessing herbicidal properties. European Patent Publication No. 0213892 discloses herbicidally active enols. These compounds possess very good levels of herbicidal activity, but at higher dose rates there can be a risk of crop phytotoxicity.
The present invention seeks to provide compositions of these herbicides for use in combination with antidotes therefor for reduction of injury to crops, especially wheat, due to phytotoxicity of these herbicides at certain dose rates or under certain conditions of use.
DESCRIPTION OF THE INVENTION
The invention provides a method of reducing phytotoxicity at a crop plant locus caused by at least one 4-benzoylisoxazole herbicide and/or 2-cyano-1,3-dione herbicide which comprises applying to the crop plant locus at least one sulfonylurea herbicide.
Surprisingly, the applicants have found that the presence of at least one sulfonylurea herbicide allows any crop phytotoxicity by the isoxazole and/or 2-cyano-1,3-dione herbicide to be reduced in the presence of at least one sulfonylurea herbicide, while maintaining a good level of weed control.
The method of the invention reduces phytotoxicity by a safening effect of the sulfonylurea. The invention also provides a method whereby the total amount of herbicide may be reduced by virtue of a synergistic effect.
Preferably the 4-benzoylisoxazole herbicide has the general formula (I):
wherein
R is hydrogen or —CO
2
R
3
;
R
1
is C
1-6
alkyl or C
3-6
cycloalkyl optionally bearing C
1-6
alkyl;
R
2
is selected from halogen (e.g. chlorine or bromine), —S(O)
p
Me CH
2
SO
q
Me, C
1-6
alkyl, C
1-6
haloalkyl (e.g. CF
3
), C
1-6
alkoxy or C
1-6
haloalkoxy;
n is two or three; p is zero, one or two; q is zero, one or two; and
R
3
is C
1-4
alkyl.
In formula (I) above R
1
is preferably cyclopropyl.
In formula (I) above preferably one group R
2
represents —S(O)
p
Me, most preferably in the 2-position of the benzoyl ring.
4-Benzoylisoxazoles of formula (I) above of particular interest in the method of the invention include the following:
A. 5-cyclopropyl-4-(2-methylsulfonyl-4-trifluoromethyl)benzoylisoxazole;
B. ethyl 5-cyclopropyl-4-(2-methylsulfonyl-4-trifluoromethyl)benzoylisoxazole-3-carboxylate;
C. ethyl 5-cyclopropyl-4-[3,4-dichloro-2-(methylthio)-benzoyl]isoxazole-3-carboxylate;
D. 5-cyclopropyl-4-[4-bromo-2-(methylsulfonylmethyl)benzoylisoxazole;
E. 5-cyclopropyl-4-(4-methylsulfonyl-2-trifluoromethyl)benzoylisoxazole; and
F. 5-cyclopropyl-4-(4-chloro-2-methylsulfonyl)benzoylisoxazole.
The letters A to F are assigned to these compounds for reference and identification hereafter.
Compounds A, B and C are preferred.
Preferably the 2-cyano-1,3-dione derivative has the formula (II):
wherein R
1
, R
2
and n are as defined above.
Compounds of formula (II) above may exist in enolic tautomeric forms that may give rise to geometric isomers around the enolic double bond. Furthermore, in certain cases the groups R
1
and R
2
may give rise to stereoisomers and geometric isomers. All such forms and mixtures thereof are embraced by the present invention.
The most preferred compound of formula (II) above is 2-cyano-3-cyclopropyl-1-(2-methylsulfonyl-4-trifluoromethylphenyl)propan-1,3-dione.
Preferably the sulfonylurea herbicide has the general formula (III):
R
4
SO
2
NR
5
C(O)NR
6
R
7
  (III)
wherein:
R
4
is selected from substituted or unsubstituted phenyl, substituted or unsubstituted thienyl, substituted or unsubstituted pyridyl, and substituted or unsubstituted imidazopyridinyl;
R
5
and R
6
are independently C
1-6
alkyl or hydrogen; or
R
7
is selected from substituted or unsubstituted triazine or substituted or unsubstituted diazine. Preferably the substituted phenyl, thienyl, pyridyl or imidazopyridinyl moieties are substituted by halogen, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, substituted or unsubstituted amido, alkylthio, alkylsulfenyl, and alkylsulfonyl. The triazine and diazine moieties are preferably substituted by alkoxy or alkyl.
In the above definition, alkyl and moieties comprising it generally contain from one to six carbon atoms and are optionally substituted by one or more atoms from group consisting of bromine, chlorine, fluorine and iodine.
Preferably the sulfonylurea herbicide has the general formula (III) with one or more of the following features:
R
4
is selected from 2-substituted phenyl, 2-substituted-3-thienyl, 3-substituted-2-pyridyl; 2-substituted-imidazo[1,2-a]pyridine;
R
5
and R
6
are independently methyl or hydrogen; and
R
7
is selected from 4,6-dimethoxy-1,3,5-triazine; 4-methoxy-6-methyl-1,3,5-triazine; 4,6-bisdifluoromethoxy-1,3-diazine, and 4,6-dimethoxy-1,3-diazine.
Even more preferably the sulfonylurea herbicide has the general formula (III) wherein:
R
4
is selected from 2-chlorophenyl; 2-methoxycarbonylphenyl, 2-haloalkylphenyl, 2-haloalkoxyphenyl, 2-methoxycarbonyl-3-thienyl, 3-dialkylamido-2-pyridyl and 2-alkylsulfonylimidazo[1,2-a]pyridine;
R
5
and R
6
are independently selected from hydrogen or methyl; and
R
7
is selected from 4,6-dimethoxy-1,3,5-triazine; 4-methoxy-6-methyl-1,3,5-triazine; 4,6-bisdifluoromethoxy-1,3-diazine; and 4,6-dimethoxy-1,3-diazine.
Preferably there are one or two sulfonylurea herbicides present selected from:
1-(2-chlorophenylsulfonyl)-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea(chlorsulfuron);
2-[4-methoxy-6-methyl-1,3,5-triazin-2-yl(methyl)carbamoylsulfamoyl]benzoic acid (tribenuron-methyl);
3-(4-methoxy-6-methyl-1,3,5-triazin-2-ylcarbamoylsulfamoyl)thiophen-2-carboxylic acid (thifensulfuron methyl);
2-(4-methoxy-6-methyl-1,3,5-triazin-2-ylcarbamoylsulfamoyl)benzoic acid (metsulfuron);
1-[2-(2-chloroethoxy)phenylsulfonyl]-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea (triasulfuron);
1-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)-phenylsulfonyl]urea (CGA-152005 or prosulfuron);
1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-dimethylcarbamoyl-2-pyridylsulfonyl)urea (nicosulfuron);
2-[4,6-bis(difluoromethoxy)pyrimidin-2-yl-carbamoylsulfamoyl]benzoic acid (primisulfuron);
N-[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]-3-ethylsulfonyl-2-pyridinesulfonamide (rimsulfuron or DPX-E9636) and
1-(2-ethylsulfonylimidazo[1,2-a]pyridin-3-ylsulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl)urea (MON 37500: CAS Registry Number 141776-32-1).
Sulfonylurea herbicides may be prepared by references found in The Pesticide Manual, 10
th
Edition, C. Tomlin editor; British Crop Protection Association, 1994, or by those known to the skilled addressee.
Most preferably there are two sulfonyl urea herbicides present. Preferably these are selected from thifensulfuron methyl, tribenuron methyl and MON 37500.
The amount of sulfonylurea herbicide used in the method of the invention varies according to a number of parameters including the weeds to be controlled, the crop to be protected, the amount and rate of herbicide applied, and the edaph

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