Abstract:
A herbicidal composition comprising metsulfuron methyl and at least one compound selected from the group consisting of pyrazosulfuron ethyl and halosulfuron methyl as active ingredients, and a method for controlling weeds comprising using the composition.

Description:
This application is a 371 of PCT/JP97/00158, filed Jan. 24, 1997. 
     FIELD OF THE INVENTION 
     The present invention relates to a herbicidal composition comprising at least two kinds of known herbicidally active ingredients, which can effectively control various harmful weeds in a paddy field. 
     BACKGROUND OF INVENTION 
     Various kinds of herbicides have been put to practical use by research and development concerning a herbicide for many years, which herbicides have contributed to laborsaving in controlling weeds and improving productivity of farm and garden crops. Development of a new herbicide having a more excellent herbicidal activity is, however, still needed. In particular, a herbicide for paddy rice is needed which can selectively control target weeds in lower dose without any phytotoxicity to paddy rice. Existing herbicides, however, do not necessarily meet these requirements. 
     Pyrazosulfuron ethyl (Common name; hereinafter referred to as Compound (I-1)), which can provide an excellent herbicidal effect with a lower dose as compared with conventional herbicides and show good safety to paddy rice, has been practically used. But pyrazosulfuron ethyl has inadequate effects on some weeds. 
     Halosulfuron methyl (Common name; hereinafter referred to as Compound (I-2)), which can provide an excellent herbicidal effect with a lower dose as compared with conventional herbicides and show good safety to corn, has been practically used for corn and suggested to apply to paddy rice. But halosulfuron methyl has inadequate effects on some weeds. 
     Metsulfuron methyl (Common name; hereinafter referred to as Compound (II)), which can also provide an excellent herbicidal effect with a lower dose as compared with conventional herbicides, has been practically used as a herbicide for wheat. Metsulfuron methyl is, however, less effective to Cyperaceae weeds and sometimes cause phytotoxicity to paddy rice with a higher dose, while it shows safety to paddy rice with a lower dose. 
     SUMMARY OF THE INVENTION 
     This invention relates to a herbicidal composition comprising Compound (II) and at least one compound selected from the group consisting of Compound (I-1) and Compound (I-2) as active ingredients (hereinafter referred to as the composition of the present invention). 
     According to the composition of the present invention, Compound (I-1), Compound (I-2) and Compound (II) can provide their herbicidal effects synergistically more than additively, and consequently the amount of each compound to be applied can be reduced. 
     The composition of the present invention is practically quite useful, since it can completely control many weeds with a low dose without any phytotoxicity to paddy rice. The composition of the present invention is highly effective to weeds in both pre-emergence soil treatment and post-emergence foliar treatment. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the composition of the present invention, Compound (II) is blended with Compound (I-1) and Compound (I-2) preferably at the ratio of 0.001-10 parts by weight of Compound (II) per 1 part by weight of Compound (I-1) and Compound (I-2), more preferably 0.01-1 parts by weight of Compound (II) per 1 part by weight of Compound (I-1) and Compound (I-2). 
     Suitable application rate of the composition of the present invention will vary depending on a type of target weed and the like. In general, the application rate is set such that it preferably corresponds to 1 g-1 kg/ha of Compound (I-1) or Compound (I-2) and 0.1-100 g/ha of Compound (II) as active ingredients, more preferably 5-100 g/ha of the former and 1-50 g/ha of the latter. 
     The composition of the present invention is usually used in a form of a formulation in which the active ingredients are mixed with a carrier usually consisting of a solid or liquid diluent. The formulation preferably also contains a surfactant. 
     Such an applicable carrier includes a solid carrier such as clay, talc, bentonite, diatomaceous earth and white carbon; and a liquid carrier such as water, alcohols (isopropanol, butanol, benzyl alcohol, furfuryl alcohol, etc.), aromatic hydrocarbons (toluene, xylene, etc.), chlorinated hydrocarbons (chlorobenzene, etc.), ethers (anisol, etc.), ketones (cyclohexanone, isophorone, etc.), esters (butyl acetate, etc.), acid amides (N-methyl pyrrolidone, etc.). 
     Such an applicable surfactant includes an anionic surfactant such as sodium alkylarylsulfonates, sodium alkylnaphthalenesulfonates, sodium dialkylsuccinates, polyoxyethylene alkylaryl ether sulfates, alkyl type of phosphates and alkylphenol type of phosphates; a nonionic surfactant such as polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene (propylene) fatty acid esters, sorbitan monooleate and polyoxyethylenesorbitan monolaurate; and a vegetable oil derivative such as polyoxyethylene hardened castor oil. 
     The composition of the present invention, if necessary, can also be added with an emulsifier, wetting agent, dispersant, binder, penetrating agent, spreader and/or stabilizer, and can be practically used in a desirable formulation such as an emulsifiable concentrate, liquid formulation, wettable powder, dust formulation, granule, granular wettable powder or flowable. 
     The composition of the present invention can be used in combination with one or more known herbicides. Preferable herbicides which are used in combination with the composition of the present invention include bensulfuron methyl (Common name), cinosulfuron (Common name), imazosulfuron (Common name), pretilachlor (Common name), esprocarb (Common name), pyrazolate (Common name), pyrazoxyfen (Common name), benzofenap (Common name), bromobutide (Common name), naproanilide (Common name), clomeprop (Common name), CNP (Common name), chlomethoxynil (Common name), bifenox (Common name), oxadiazon (Common name), mefenacet (Common name), butachlor (Common name), butenachlor (Common name), dithiopyr (Common name), benfuresate (Common name), pyributicarb (Common name), benthiocarb (Common name), dimepiperate (Common name), molinate (Common name), butamifos (Common name), quinclorac (Common name), cinmethylin (Common name), propanil (Common name), simetryn (Common name), bensulide (Common name), dimethametryn (Common name), methyldymron (Common name), anilofos (Common name), MCPA, MCPB, cafenstrole (Common name), thenylchlor (Common name), 2&#39;,3&#39;-dichloro-ethoxymethoxybenzanilide (test name: HW-52), 1-(2-chlorobenzyl)-3-(α, α-dimethylbenzyl)urea (test name: JC-940), N-(2-fluoro-4-chloro-5-cyclopentyloxyphenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione (test name: KPP-314), n-butyl-(R)-2-[4-(2-fluoro-4-cyanophenoxy)phenoxy]propionate (test name: DEH-112), methyl 2-[(4,6-dimethoxypyrimidin-2-yl)oxy]-6-[1-(methoxyimino)ethyl]benzoate (test name: KUH-920), 2-[2-(3-chlorophenyl)-2,3-epoxypropyl]-2-ethylindane-1,3-dione (test name: MK-243), bentazone (Common name), dymron (Common name) and compounds listed in WO-9321162 and JP-A-6-184115. 
     The composition of the present invention can be used as a herbicidal composition for paddy field in both foliar treatment and soil treatment under flooded condition. Paddy weeds include Alismataceae weeds represented by Alisma canaliculatum, Sagittaria trifolia, Sagittaria pygmaea and the like; Cyperaceae weeds represented by Cyperus difformis, Cyperus serotinus, Scirpus juncoides, Eleocharis kuroauwai and the like; Scrothulariaceae weeds represented by Lindernia pyxidaria and the like; Potenderiaceae weeds represented by Monochoria vaginalis and the like; Potamogetonaceae weeds represented by Potamogeton distinctus and the like; Lythraceae weeds represented by Rotala indica and the like; and Gramineae weeds represented by Echinochloa crus-galli and the like. 
     A synergistic herbicidal effect of a herbicide mixture can be explained as follows. Two herbicidally active compounds, each of which often has defects in its herbicidal activity, may be combined each other to provide a higher activity than an expected activity which is an activity obtained by simply adding each activity of them. Such a higher activity is called a synergistic effect. An expected activity from a specific combination of two herbicides can be estimated as follows (See Colby S. R., &#34;Estimation of a synergistic and antagonistic effect of combined herbicides&#34;, Weed, Vol. 15, pp. 20-22 (1967).). 
     
         E=α+β-(α×β/100) 
    
     α: a control rate achieved by Herbicide A when it is applied in the application rate of &#34;a&#34; kg/ha; 
     β: a control rate achieved by Herbicide B when it is applied in the application rate of &#34;b&#34; kg/ha; 
     E: an expected control rate when Herbicide A and B are applied in the application rates of &#34;a&#34; kg/ha and &#34;b&#34; kg/ha, respectively. 
     Thus, when a control rate actually achieved is higher than the expected control rate obtained by the above calculation, it can be concluded that the effect provided by the combination is a synergistic effect. 
    
    
     EXAMPLES 
     The following Examples illustrate the composition of the present invention. The compounds, production amounts, formulations according to the present invention, however, should not be limited to the Examples. In the following description, &#34;part(s)&#34; signifies part(s) by weight. 
     
         ______________________________________[Wettable powder]      parts______________________________________The composition of the present invention                  0.1-80Solid carrier          10-90Surfactant              1-10Others                 1-5______________________________________ 
    
     (Others, for example, include a coagulation preventing agent and the like.) 
     
         ______________________________________                parts______________________________________[Emulsifiable Concentrate]The composition of the present invention                  0.1-30Liquid carrier          55-95Surfactant             4.9-15[Flowable]The composition of the present invention                  0.1-70Liquid carrier          15-65Surfactant               5-12Others                   5-30______________________________________ 
    
     (Others, for example, include an anti-freezing agent and a thickener and the like.) 
     
         ______________________________________                parts______________________________________[Granular Wettable Powder] (Dry Flowable)The composition of the present invention                  0.1-90Solid carrier          5-70Surfactant             1-30[Liquid Formulation]The composition of the present invention                  0.01-30Liquid carrier         0.1-50Water                    50-99.99Others                 0.1-10[Granule]The composition of the present invention                  0.01-10Solid carrier            90-99.99Others                 0-10______________________________________ 
    
     
         ______________________________________Formulation Example 1: Granule               parts______________________________________Compound (I-1)       5Compound (II)        1Bentonite           55Talc                39______________________________________ 
    
     The above ingredients are homogeneously blended and ground, to which then a small amount of water is added, and the resulting mixture is kneaded with stirring, granulated by an extrusion granulator and dried to formulate a granule. 
     
         ______________________________________Formulation Example 2: Granular Wettable Powder (Dry Flowable)                         parts______________________________________Compound (I-1)                60Compound (II)                 10Isobam No. 1 (trademark)      15(anionic surfactant: Kuraray Isoprene Chemical Co., Ltd.)Vanilex N (trademark)          5(anionic surfactant: Sanyo Kokusaku Pulp K.K.)Carplex #80 (trademark)       10(white carbon: Shionogi Pharmaceutical Co., Ltd.)______________________________________ 
    
     The above ingredients are homogeneously blended and finely ground to formulate a dry flowable. 
     
         ______________________________________Formulation Example 3: Wettable powder                     parts______________________________________Compound (I-1)            40Compound (II)             8Zeeklite PFP (trademark)  45(kaolin type clay: Zeeklite Industries Co., Ltd.)Sorpol 5050 (trademark)   2(anionic surfactant: Toho Chemical Co., Ltd.)Runox 1000 C (trademark)  3(anionic surfactant: Toho Chemical Co., Ltd.)Carplex #80 (trademark)   2(coagulation preventing agent)(white carbon: Shionogi Pharmaceutical Co., Ltd.,)______________________________________ 
    
     The above ingredients are homogeneously blended and ground to formulate a wettable powder. 
     
         ______________________________________Formulation Example 4: Granule               parts______________________________________Compound (I-2)       5Compound (II)        1Bentonite           55Talc                39______________________________________ 
    
     The above ingredients are homogeneously blended and ground, to which then a small amount of water is added, and the resulting mixture is kneaded with stirring, granulated by an extrusion granulator and dried to formulate a granule. 
     
         ______________________________________Formulation Example 5: Granular Wettable Powder (Dry Flowable)                         parts______________________________________Compound (I-2)                60Compound (II)                 10Isobam No. 1 (trademark)      15(anionic surfactant: Kuraray Isoprene Chemical Co., Ltd.)Vanilex N (trademark)          5(anionic surfactant: Sanyo Kokusaku Pulp K.K.)Carplex #80 (trademark)       10(white carbon: Shionogi Pharmaceutical Co., Ltd.)______________________________________ 
    
     The above ingredients are homogeneously blended and finely ground to formulate a dry flowable. 
     
         ______________________________________Formulation Example 6: Wettable powder                     parts______________________________________Compound (I-2)            40Compound (II)             8Zeeklite PFP (trademark)  45(kaolin type clay: Zeeklite Industries Co., Ltd.)Sorpol 5050 (trademark)   2(anionic surfactant: Toho Chemical Co., Ltd.)Runox 1000 C (trademark)  3(anionic surfactant: Toho Chemical Co., Ltd.)Carplex #80 (trademark)   2(coagulation preventing agent)(white carbon: Shionogi Pharmaceutical Co., Ltd.)______________________________________ 
    
     The above ingredients are homogeneously blended and ground to formulate a wettable powder. 
     The following Test Examples specifically show that the composition of the present invention is useful as a herbicide. 
     Test Example 1: Test on Herbicidal Effect by Pre-emergence Treatment Under Flooded Condition 
     An alluvial soil was placed in 1/5000 are Wagner pots and then water was poured thereinto to puddle the soil to prepare a flooded condition with 4 cm of the depth of water. After seeds of Monochoria vaginalis and Scirpus juncoides are sown and tubers of Sagittaria pygmaea and Cyperus serotinus are placed on the soil, 2.5-leaf stage rice seedlings were transplanted. On the day of transplanting the rice seedlings, a predetermined concentration of suspension of each test compound, which was prepared using a wettable powder formulated by way of experiment in accordance with the above formulation example, was dropped onto the water surface with a measuring pipette. Three weeks after the application of each compound, fresh weights of aerial parts of each weed and rice plant were weighed to determine a control rate (%) using the following equation. 
     A control rate (%)=[1-(fresh weight of aerial parts of the treated weeds and rice plants)/(fresh weight of aerial parts of the untreated weeds and rice plants)]×100 
     The results obtained are shown in Table 1 and Table 2. 
     In these tables, symbols represent the following meanings; 
     A: Monochoria vaginalis, B: Scirpus juncoides, C: Sagittaria pygmaea, D: Cyperus serotinus, R: transplanted rice. 
     
                       TABLE 1______________________________________Herbicidal effects of single formulations (control rates (%))   Application RateCompound   (g a.i./ha) A       B   C     D   R______________________________________Compound   3           46      72  67    55  0(I-1)   4           65      80  71    60  0   6           72      85  82    75  0   9           87      94  95    90  0   10          93      98  98    95  0   12          98      99  99    98  0Compound   1           65      47  23     5  0(II)    3           88      87  75    20  0   4           92      95  80    31  5   6           98      99  92    42  28______________________________________ 
    
     
                                           TABLE 2__________________________________________________________________________Herbicidal effects of the composition of the present invention;actually found values (F) and expected values (E) (control rates (%))  Application        Plant  Rate  A    B    C    D    RCompound  (gai/ha)        (F)           (E)             (F)                (E)                  (F)                     (E)                       (F)                          (E)                            (F)                              (E)__________________________________________________________________________Compound  3 + 1 100           81             100                85                  100                     75                        86                          57                            0 0(I-1) + (II)  3 + 3 100           95             100                97                  100                     96                       100                          64                            0 0  9 + 1 100           94             100                96                  100                     92                        96                          91                            0 0  9 + 3 100           98             100                99                  100                     99                       100                          92                            0 0__________________________________________________________________________ (In the table, the expected values are those calculated with the above Colby&#39;s equation. In the application rate of active ingredient of the mixture composition, a left value is the application rate of Compound (I1 and a right value is the application rate of Compound (II).) 
    
     
                       TABLE 3______________________________________Herbicidal effects of single formulations (control rates (%))    Application RateCompound (g a.i./ha) A       B   C     D   R______________________________________Compound 3           39      65  60    43  0(I-2)    4           64      75  70    55  0    6           70      84  78    71  0    9           85      90  95    86  0    10          95      97  96    96  0    12          98      99  99    98  0______________________________________ 
    
     
                                           TABLE 4__________________________________________________________________________Herbicidal effects of the composition of the present invention;actually found values (F) and expected values (E) (control rates (%))  Application        Plant  Rate  A    B    C    D    RCompound  (gai/ha)        (F)           (E)             (F)                (E)                  (F)                     (E)                       (F)                          (E)                            (F)                              (E)__________________________________________________________________________Compound  3 + 1 100           79             100                81                  100                     69                        83                          46                            0 0(I-2) + (II)  3 + 3 100           93             100                95                  100                     90                        90                          57                            0 0  9 + 1 100           95             100                95                  100                     96                       100                          87                            0 0  9 + 3 100           98             100                99                  100                     99                       100                          89                            0 0__________________________________________________________________________ (In the table, the expected values are those calculated with the above Colby&#39;s equation. In the application rate of active ingredient of the mixture composition, a left value is the application rate of Compound (I2 and a right value is the application rate of Compound (II).) 
    
     Test Example 2: Test on Herbicidal Effect by Growing Stage Treatment Under Flooded Condition 
     An alluvial soil was placed in 1/5000 are Wagner pots and then water was poured thereinto to puddle the soil to prepare a flooded condition with 4 cm of the depth of water. Seeds of barnyardgrass (Echinochloa crus-galli) and rice are sown. When the barnyardgrass grew to 2.5-leaf stage, a diluted solution of test compound was dropped onto the water surface with a measuring pipette so that predetermined amount of the compound was applied. Three weeks after treatment with the compound, herbicidal effects on the barnyardgrass and rice were evaluated according to the following criteria. The results obtained are shown in Table 5. 
     Evaluation Criteria 
     5: Completely killed or control rate is at least 90%; 
     4: Control rate is at least 70% to less than 90%; 
     3: Control rate is at least 40% to less than 70%; 
     2: Control rate is at least 20% to less than 40%; 
     1: Control rate is at least 5% to less than 20%; 
     0: Control rate is less than 5%. 
     The control rate was determined on the basis of visual observation. 
     
                       TABLE 5______________________________________   Application Rate               PlantCompound  (g a.i./ha)   Barnyardgrass                              Rice______________________________________Compound  3             2          0(I-1)     9             3          0Compound  3             2          0(I-2)     9             3          0Compound  3             0          0(II)      9             1          1Compound  3 + 1         4          0(I-1) + (II)     3 + 3         5          0     9 + 1         5          0     9 + 3         5          0Compound  3 + 1         4          0(I-2) + (II)     3 + 3         5          0     9 + 1         5          0     9 + 3         5          0______________________________________ 
    
     As apparent from the above results, the composition of the present invention provides much higher effects, which is synergistic effects, than additive effects expected from Compound (I-1), Compound (I-2) and Compound (II). The composition of the present invention can selectively control target weeds with a lower dose as compared with conventional herbicidal compositions.