Plant protecting and regulating compositions – Plant growth regulating compositions – Plural active ingredients
Reexamination Certificate
2000-05-09
2001-04-10
Dees, Jose′ G. (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Plural active ingredients
C504S212000, C504S213000
Reexamination Certificate
active
06214769
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods for controlling weeds using herbicides, in particular to methods of controlling weeds resistant to acetolactate synthase (ALS)-inhibiting herbicides.
BACKGROUND OF THE INVENTION
Four chemistry classes of acetolactate synthase (ALS)-inhibiting herbicides have been developed and are commercially available for agronomic weed control. They are sulfonylureas such as chlorsulfuron (e.g., GLEAN® from DuPont), imidazolinones such as imazethapyr (e.g., PURSUIT® from American Cyanamid Co.), triazolopyrimidines such as flumetsulam (e.g., BROADSTRIKE® from DowElanco), and pyrimidinylthiobenzoates such as pyrithiobac (e.g., STAPLE® from DuPont). Because of their low use rates, low mammalian toxicity, good crop selectivity, and high efficacy on target weed species, these herbicides have gained widespread use and popularity in weed control in, e.g., corn, soybeans, wheat, barley, cotton, sorghum, rice, and many other crops. Currently, a wide variety of ALS-inhibiting herbicides are commercially available or under development.
However, weed resistance has recently become a great concern in the industry. Weed resistance to ALS-inhibiting herbicides was first recognized five years after the commercial launch of the sulfonylurea herbicide, chlorsulfuron. See Mallory-Smith et al.
Weed Tech
. 4:163-168 (1990). Poor rotation of herbicides to dissimilar modes of action, the high efficacy of ALS-inhibiting herbicides, and the relatively high frequency of naturally occurring mutations have been the contributory factors for the widespread weed resistance to ALS-inhibiting herbicides. Many weeds have developed such resistance. In fact, the number of weed species resistant to ALS-inhibiting chemistries is second only to inhibitors of Photosystem II (e.g., triazines). See Heap,
Pesticide Science
51:235-234 (1997).
Based on the analysis of the resistant weeds selected from natural weed populations, mutations at five different positions in the primary ALS peptide sequence have been identified to be responsible for ALS-inhibiting herbicide resistance. As summarized in Table 1, each one of the five mutations has a unique cross-class resistance characteristic.
TABLE 1
Cross-Class Resistance to ALS-Inhibiting Herbicides
Amino
acid
ALS-Inhibiting Herbicide Classes
position of
Imidazo-
Triazolo-
Pyrimidinylthio-
mutation*
Sulfonylureas
linones
pyrimidines
benzoates
A
122
R
P
197
R
R
A
205
R
R
R
R
W
574
R
R
R
R
S
653
R
R
*refers to the amino acid equivalent position in
Arabidopsis thaliana
The level of resistance by a weed species having a particular mutation may vary with individual members in one ALS-inhibiting herbicide class. Nevertheless, in general the cross class resistance remains consistent. In other words, if a particular weed is resistant to one member of a particular ALS-inhibiting herbicide class, it will be resistant to all members of that class.
Certain other herbicides which control weeds by a mode of action other than inhibiting acetolactate synthase may be useful in controlling weeds resistant to ALS-inhibiting herbicides. However, none of them possesses all the desirable attributes ALS-inhibiting herbicides have, i.e., low mammalian toxicity, low use rates, good crop selectivity, and high efficacy.
SUMMARY OF THE INVENTION
The present invention provides a method for controlling ALS-inhibiting herbicide resistant weeds using a compound which exhibits the desirable characteristics of low mammalian toxicity, low use rate, good crop selectivity, and high efficacy.
The method of this invention utilizes the herbicidal activity of the N-[(1,3,5-triazin-2-yl)-aminocarbonyl]-benzenesulfonamide compounds of formula I
wherein
R
1
is lower alkyl (e.g., C
1-5
alkyl such as CH
3
, C
2
H
5
, and C
3
H
7
);
R
2
is trihalomethyl (e.g., CF
3
, CCl
3
, and CBr
3
);
R
3
is hydrogen or lower alkyl (e.g., C
1-5
alkyl such as CH
3
, C
2
H
5
, and C
3
H
7
), or agriculturally useful salts thereof.
The present compounds bear great similarity to sulfonylurea herbicides in chemical structure, and thus would be expected to exhibit weed control properties similar to those of sulfonylurea herbicides. In addition, as discussed above, because of the cross class resistance phenomena, weeds resistant to sulfonylureas would be expected to be resistant to the present compounds as well. Nevertheless, it has been surprisingly discovered that compounds of formula I are highly effective in controlling not only weeds resistant to sulfonylurea herbicides but also weeds resistant to other ALS-inhibiting herbicide classes.
Accordingly, the method of this invention comprises applying a herbicidally effective amount of a compound of formula I, or agriculturally useful salts thereof, to control weeds resistant to an acetolactate synthase (ALS)-inhibiting herbicide.
In a preferred embodiment, a herbicidally effective amount of the compound 1-[(4-methoxy-6-trifluoromethyl)-1,3,5-triazin-2-yl]-3-(2-trifluoromethyl-benzenesulfonyl)-urea or an agriculturally useful salt thereof, is applied to inhibit the undesirable growth of ALS-inhibiting herbicide resistant weeds.
In another embodiment of this invention, a compound of formula I is used in combination with one or more herbicides having a different mode of herbicidal action than inhibiting acetolactate synthase. Non-limiting examples of such one or more herbicides include auxinic herbicides, auxin transport inhibitors, photosynthesis inhibitors, and cell division inhibitors.
The N-[(1,3,5-triazin-2-yl)-aminocarbonyl]-benzenesulfonamide compounds used in the method of this invention are highly effective in controlling weeds resistant to ALS-inhibiting herbicides while exhibiting desirable levels of mammalian toxicity, use rate and crop selectivity that are comparable to those of ALS-inhibiting herbicides. Therefore, the present invention provides an effective method for controlling ALS-inhibiting herbicide resistant weeds and, when properly utilized in combination with other herbicides, for preventing the development of new ALS-inhibiting herbicides resistant weeds.
In addition, often in a particular locus, ALS inhibitor resistant weeds develop from, and cohabit with, ALS inhibitor sensitive wild type weeds. The compounds used in this invention are effective against ALS inhibitor sensitive weeds as well as ALS inhibitor resistant weeds. Thus, the method of this invention is significantly more effective in controlling an entire weed population in a particular locus than methods in the art using conventional ALS-inhibiting herbicides.
The foregoing and other advantages and features of the invention, and the manner in which the same are accomplished, will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying examples, which illustrate preferred and exemplary embodiments.
REFERENCES:
patent: 5478789 (1995-12-01), Mayer et al.
patent: 5488029 (1996-01-01), Hamprecht et al.
patent: 6043196 (2000-03-01), Mayer et al.
patent: 9965314 (1999-12-01), None
Burdick Bruce
James Terance
Kirksey Bruce
Wright Terry R.
Alston & Bird LLP
BASF Corporation
Dees Jose′ G.
Pryor Alton
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