Conditioning of herbicidal chloroacetamides

There is provided a method for protecting crop plants from phytotoxic injury caused by a chloroacetamide herbicide by co-applying a non-phytotoxic, conditioning effective amount of a benzothiadiazinone derivative. The method is particularly effective in protecting dry edible beans from phytotoxicity when dimethenamid is applied postemergence.

BACKGROUND OF THE INVENTION 
While herbicides have gained a high degree of commercial success because it 
has been shown that such compounds can increase crop yields and reduce 
harvesting costs, some of these herbicides have been shown to injure crop 
plants at rates necessary to control weed growth. To be effective, a 
herbicide must cause minimal damage, and preferably no damage to the 
beneficial crop while maximizing damage to weed species which infest the 
locus of a crop. The injury caused by various known herbicides varies 
depending on a number of factors some of which include the type of 
herbicidal formulation applied to the crop plants, the type of crop, the 
type of soil a crop is growing in and environmental factors such as 
temperature or wetness. While a herbicide may not injure a crop plant 
under one set of conditions, it is possible that the same herbicide could 
cause injury under a different set of conditions. 
To protect a crop species from herbicidal injury along with concomitant 
herbicidal effectiveness on weed species, use of chemical compounds called 
safeners or antidotes have been employed. The use of safeners with 
herbicidally active compounds is a widely accepted agricultural practice. 
Safeners are used on crops including agronomic and vegetable species. The 
terms safener, safening agent, antidote, antagonistic agent and crop 
protectant are often used terms in the art and denote a compound capable 
of reducing the phytotoxicity of a herbicide to a crop plant or crop seed 
but which is not phytotoxic itself to the crop plant or crop seed and 
which does not affect the herbicides' activity against targeted weeds. 
Crop species susceptible to herbicidal injury may also benefit from the use 
of compounds called conditioners. Unlike safeners, these compounds are 
herbicidal to some undesirable plant species when applied at conditioning 
rates; but like safeners, conditioners lower the phytotoxic effect of 
herbicidal compounds on a crop plant or seed without being phytotoxic 
itself to the crop plant. 
The chloroacetamide herbicide known as dimethenamid has been found to be a 
very effective herbicide with broad general activity against a wide 
variety of undesirable weed species. Chloroacetamides and particularly 
thiophene based chloroacetamides (hereinafter referred to as 
"thiopheneamides") including dimethenamid are disclosed in U.S. Pat. No. 
4,666,502. Additionally, the (S) optical isomer of dimethenamid is 
disclosed in U.S. Pat. No. 5,457,085 (application Ser. No. 310,198, filed 
Sep. 21, 1994). Both of these U.S. Patents are incorporated herein in 
their entirety by reference. Dimethenamid is commercially available, for 
example, under the trade name FRONTIER herbicide (Sandoz Crop Protection, 
Inc., Des Plaines Ill.) 
Although selective in many major crops, in certain specific crops 
dimethenamid has been found to adversely effect or interfere with the 
culture of the desirable crop species. Therefore the effective use of the 
herbicide for controlling weeds in the presence of such crops or under 
specific conditions is further enhanced by the addition of conditioners 
and/or safeners. 
It is therefore an object of the present invention to provide a method of 
reducing phytotoxicity to a crop plant due to the injury caused by a 
thiopheneamide herbicide without decreasing the herbicidal efficacy of 
said thiopheneamide which comprises applying to the crop plant or a locus 
where control of undesirable weeds is desired an effective conditioning 
amount of a benzothiadiazinone derivative. 
It is also an object of the present invention to provide a herbicidal 
composition comprising a herbicidally effective amount of a thiopheneamide 
herbicide in combination with a non-phytotoxic, conditioning-effective 
amount of a benzothiadiazinone compound. 
These and other objects of the present invention will become more apparent 
from the detailed description set forth below. 
SUMMARY OF THE INVENTION 
The present invention relates to a method for reducing the phytotoxicity of 
a herbicidally effective amount of a thiopheneamide compound on a crop 
plant comprising co-applying to the crop plant or locus where herbicidal 
control is desired an non-phytotoxic, conditioning-effective amount of a 
conditioner compound having the structural formula (B) 
##STR1## 
wherein R is C.sub.1-6 alkyl. 
Preferably, the method comprises co-applying to the crop plant or a locus 
where control is desired a herbicidally effective amount of a 
thiopheneamide compound of formula (A) 
##STR2## 
wherein R and R.sup.2 are independently H, Cl, Br, F, C.sub.1-4 alkyl and 
C.sub.1-4 alkoxy; R.sup.1 is H, Cl, Br, F, or C.sub.1-4 alkyl; R.sup.3 is 
C.sub.1-8 alkyl; and A is CH.sub.2, CH.sub.2 --CH.sub.2 or a 
monomethylated derivative thereof and a non-phytotoxic, 
conditioning-effective amount of a compound according to formula (B). 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention relates to a method of reducing the phytotoxicity of 
a herbicidally effective thiopheneamide compound comprising applying a 
compound of formula (B), defined herein as a conditioner, to the seed of 
the crop to be conditioned, to the foliage of the crop or to the soil 
surrounding the crop or crop seed. The herbicidal compounds and the 
conditioner compounds of this invention are known in the art. 
Herbicides which are suitable for use in the present invention include 
thiopheneamide herbicides as generally disclosed in U.S. Pat. No. 
4,666,502 along with methods of their production. An especially preferred 
compound is 
(RS)-2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl) 
acetamide, a commercially available herbicide known by the common name 
"dimethenamid". Also preferred are derivatives of dimethenamid including 
salts and esters as well as isomers thereof. Although dimethenamid and 
some of its derivatives have been used with success in certain crops, 
dimethenamid has been found to be phytotoxic in certain crops and under 
certain environmental conditions when applied at rates necessary for 
effective control of undesired vegetation. 
Surprisingly it has been found that thiopheneamide herbicides can be 
conditioned by applying to the crop plant or locus where control of 
undesirable weed species is desired a benzothiadiazinone dioxide of 
formula B. The preferred conditioner compound of the present invention is 
3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide, known by the 
common name "bentazone" or "bentazon". Bentazon(e) is a well known 
compound and disclosed in U.S. Pat. No. 3,708,277 along with methods for 
its production. Bentazon(e) is also used as a herbicide; it is generally 
used as a selective postemergence herbicide for the control of specific 
broadleaf weeds, such as common cocklebur, velvetleaf, ragweeds and the 
like. Bentazon(e) does not control grasses and therefore is used in 
conjunction with other grass- and broadleaf weed herbicides. 
The terms "herbicide" or "herbicidal" are used herein to denote the 
inhibitive control or modification of undesired plant growth. Inhibitive 
control and modification include all deviations from natural development 
such as, for example, total killing, growth retardation, defoliation, 
desiccation, regulation, stunting, tillering, stimulation, leaf burn and 
dwarfing. The term "herbicidally-effective" is defined as the amount of 
herbicide which controls or causes a modifying effect when applied to the 
undesired plants themselves or to the area or locus where control or 
modification is desired. The term locus may include soil, seed, seedlings, 
the crop plant, crop seed, weed plant and vegetation. The term "plant or 
plants" is meant to include germinate seed, emerging seedlings, rhizomes 
and established vegetation. 
The term safener, antidote and other like terms denote a compound which is 
capable of reducing the phytotoxicity of an herbicide to a crop plant, is 
non-phytotoxic to the crop plant, and is not herbicidal to plants when 
applied at a safening effective rate. 
The term "conditioner" as used herein is defined as a compound which is 
capable of reducing the phytotoxicity of a thiopheneamide herbicide to a 
crop plant, is non-phytotoxic to the crop plant and is herbicidal to some 
weed species when applied at effective conditioning amounts. Additionally, 
the conditioner as defined herein does not adversely affect the herbicidal 
activity of a thiopheneamide when the conditioner is used in combination 
with the thiopheneamide compound. While the conditioning compounds of this 
invention are herbicidal themselves, it will be appreciated by one skilled 
in the art, that a conditioning compound may not be herbicidal for all 
weeds. 
The term "non-phytotoxic" is defined as an amount of safener or conditioner 
which causes at most minor injury or no injury to the desired crop 
species. 
The term "conditioning-effective amount" is defined as the amount of 
conditioner required to decrease the extent of injury caused by a 
thiopheneamide herbicide to the desired crop species. Phytotoxicity or 
injury to a desired crop species is manifested in numerous ways well known 
to those skilled in the art and includes without limitation, leaf burning, 
leaf distortion, stunting, leaf spotting and all deviations from natural 
development and acceptable development. 
A preferred embodiment of the invention comprises a method of reducing the 
phytotoxicity of a thiopheneamide herbicide to a crop plant comprising 
applying to the crop plant or locus where herbicidal control is desired a 
herbicidally effective amount of a thiopheneamide herbicide and a 
non-phytotoxic, conditioning-effective amount of 
3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide. 
Another embodiment of the invention includes a herbicidal composition 
comprising a herbicidally effective amount of a thiopheneamide herbicide 
in combination with a non-phytotoxic, conditioning-effective amount of a 
benzothiadiazinone compound wherein the injury caused to a crop plant from 
the thiopheneamide herbicide is reduced by the conditioning compound. 
The conditioning of crops from the postemergence application of 
thiopheneamide herbicides may be effected by allowing the crop plant to 
grow until for example, the unifoliate or trifoliate leaf stage then 
spraying with an aqueous solution of the invention. Additionally the 
invention may be practiced by applying a composition of the invention to 
the soil preemergence. However, the thiopheneamide compound and 
conditioner are applied in co-application. Co-application is understood to 
mean concurrent, or immediate sequential application (within 24 hours), 
application as a tank mix or application of fixed combination premixes. 
The present invention may be used as a means of controlling a large range 
of broadleaf and grassy weeds in a crop locus wherein the crops include 
for example, cereals, such as corn; leguminous crops, such as soybean, 
peanuts, Phaseolus beans, and dry edible beans; cotton; sugarbeet; and 
sunflower. In a preferred embodiment the invention can be used to 
selectively control undesirable plants when the crop plant is a leguminous 
plant and wherein the chloroacetamide herbicide, and in particular a 
thiopheneamide herbicide, causes phytotoxicity to the leguminous crop 
plant. Therefore, the invention further includes a method of protecting a 
leguminous crop plant from injury due to a chloroacetamide herbicide 
comprising co-applying to the plant or a locus where herbicidal control is 
desired a herbicidally effective amount of a chloroacetamide herbicide and 
a non-phytotoxic conditioning effective amount of a compound corresponding 
to the formula 
##STR3## 
wherein R is C.sub.1-6 alkyl and said conditioner being conditioning 
active with said chloroacetamide herbicide on said leguminous crop plant. 
The amount of a given conditioner to be utilized in combination with the 
herbicide of this invention and the manner of its utilization and 
resulting efficacy can vary according to various parameters such as the 
particular conditioner to be applied, the crop which is to be protected, 
the amount or rate of herbicide to be applied and the soil and climatic 
conditions of the agricultural environment in which the mixture is to be 
applied. The selection of a specific conditioner for use in the herbicidal 
composition, the manner in which it is to be applied (for example, tank 
mix, in-furrow application or seed treatment) and the determination of 
activity which is conditioning can be readily performed utilizing test 
procedures in accordance with common practice in the art. 
Although the weight ratio of thiopheneamide herbicide and conditioner will 
vary depending upon the crop to be protected, weed to be inhibited and the 
specific herbicidal compound and conditioner used, the ratio will be in 
the range of from about 0.1:1.0 to about 30:1 (exclusive of auxiliary 
ingredients). A preferred weight ratio is from about 15:1 to about 1:15. 
An even more preferred weight ratio is 5:1 to about 1:5. In general, the 
effective thiopheneamide herbicidal amounts are in the range of about 0.01 
to about 8.0 kg/ha. The preferred range is from about 0.1 to about 4.0 
kg/ha and more preferred is the range from about 0.2 to about 3.0 kg/ha. 
The effective conditioning amount of a conditioner will usually be 
determined on economic ratios for the most effective amount usable. It is 
understood that a non-phytotoxic amount of a conditioning compound with 
respect to a particular crop plant will be employed. However, the amount 
used may also have an herbicidal effect on undesirable plant species and 
therefore have an additive or even synergistic effect when used in 
combination with the thiopheneamide herbicides disclosed herein. The 
amount of conditioner will generally be in the range of about 0.01 to 
about 10.0 kg/ha and a preferred range is from about 0.1 to about 4.0 
kg/ha. 
The compounds of the invention can be formulated in the same manner in 
which herbicides are generally formulated. The object of the formulation 
is to apply the compounds to the locus where control is desired by 
conventional methods. 
Useful formulations of the invention include dusts, granules, 
microcapsules, pellets, solutions, suspensions, emulsions, emulsifiable 
concentrates and the like. They are obtained by conventional manner, e.g. 
by mixing the compounds with diluent(s). Many of these can be applied 
directly to the locus. Application of the thiopheneamide herbicide and 
conditioner for co-application will vary depending upon climatic 
conditions, season weeds to be controlled and the like. In general, the 
formulations include from about 0.01% to 99% by weight of the active 
herbicide and conditioner ingredients and optionally at least about 0.1% 
to about 20% surfactant or 1% to about 99.9% solid or liquid inert 
diluent(s). Surfactant as used herein means a herbicidally acceptable 
material which imparts emulsifiability, spreading, wetting, dispersiblity 
or other surface-modifying properties. Diluent as used herein means a 
liquid or solid herbicidally acceptable material used to dilute a 
concentrated material to a useable or desirable strength.

BIOLOGICAL EVALUATION 
The following examples are provided for illustrative purposes only and are 
not intended to limit the invention in any way. 
EXAMPLE 1 
Postemergence Weed Control in Dry Edible Beans: 
Dry edible Great Northern beans seeds (Beryl) are planted in field plots 15 
feet wide by 40 feet long in sandy loam soil with 1% organic matter and pH 
7.8 in Nebraska. The experimental design is a randomized complete block 
with 4 replicates. Post emergence treatments of herbicide and conditioner 
are applied at the unifoliate leaf stage, approximately 14 days after 
planting. Compounds are applied with a tractor mount sprayer calibrated to 
deliver 21 gallons per acre. Herbicide and conditioner treatment included 
X-77 at a rate of 25% per volume of carrier and nitrogen 28% (N) is added 
at a rate of 2.5% per volume of carrier. X-77 is a non-ionic wetting agent 
containing alkylaryl polyoxyethylene, glycols, free fatty acids and 
isopropanol (Valent, Richmond, Calif.). Dry edible bean visual injury in 
the form of leaf chlorosis, browning and plant stunting is evaluated 4, 
11, 18 and 24 days after treatment. Visual injury is reported on a scale 
of 0 to 100 with 0 equal to no injury and 100 equal to complete kill in 
Table 1. Bean yield is determined 2 months after planting. The results are 
summarized in Tables 1 and 2 wherein 
F is FRONTIER herbicide, 
(RS)-2-chloro-N-(2,4-dimethyl-3-thienyl)-N-(2-methoxy-1-methylethyl) 
acetamide, (common name "dimethenamid" Sandoz Crop Protection, Des 
Plaines, Ill.!); 
B is the conditioner, BASAGRAN herbicide, 
3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide; (common name 
"bentazon(e)" BASF Corp, Research Triangle Park, N.C.!); 
AMARE is redroot pigweed; CHEAL is common lambquarters; SOLSA is hairy 
nightshade; POROL is common purslane and ECHCG is barnyardgrass. 
TABLE 1 
______________________________________ 
Conditioning of Dimethenamid by Bentazon(e) 
Herbicide + 
Rate % Injury (days after treatment) 
Bean Yield 
Conditioner 
(lb a.i./a) 
4 11 18 24 (bu/a) 
______________________________________ 
Untreated 0.0 0.0 0.0 0.0 35 
B 0.5 0.0 0.0 5.3 1.3 54 
F + B 1.0 + 0.5 
5.0 3.8 3.8 0.0 61 
F 1.0 30.0 30.0 16.3 9.5 39 
______________________________________ 
TABLE 2 
______________________________________ 
Mean Percent Weed Control 24 Days After Treatment 
Her- 
bicide + 
Con- Rate 
ditioner 
(lb a.i./A) 
AMARE CHEAL SOLSA POROL ECHCG 
______________________________________ 
Untreated 
-- 20 21 21 33 20 
B 0.5 40 74 81 81 28 
F + B 1.0 + 0.5 
98 99 99 99 97 
F 1.0 52 52 59 99 97 
______________________________________