Heteric EO/PO block copolymers as adjuvants for herbicidal formulations
FIELD OF THE INVENTION 
     The invention relates to the use of liquid heteric EO/PO, wherein EO is ethylene oxide and PO is propylene oxide, block copolymers, containing at least 30% by weight EO, as a tank mix adjuvant for enhancing the weed controlling activity of herbicidal formulations. 
     BACKGROUND OF THE INVENTION 
     The use of surfactants as adjuvants for enhancing herbicide uptake is known. Detailed discussions of the use of surfactants in agrochemical formulations are described in Surfactants in Agrochemicals, Tharwat F. Tadros, Marcel Decker, Inc. Surfactant Science Series, 1995 and Adjuvants for Herbicides, Weed Science Society of America, 1982, both publications incorporated by reference herein. 
     Further, U.S. Pat. No. 4,931,080, issued Jun. 5, 1990 to Chan and U.S. Pat. No. 5,047,079, issued Sep. 10, 1991 to Djafar et al, both disclose solid weed killing compositions comprising N-phos-phonomethyl-N-carboxymethyl herbicides and nonionic surfactants such as PLURONIC® surfactants which are EO/PO block copolymers. In U.S. Pat. No. 5,104,647, issued Apr. 14, 1992, Policello discloses a surfactant blend comprising an organosilicone compound and a polyalkylene oxide copolymer, such as PLURONIC® surfactant, useful as an agricultural adjuvant. Finally, U.S. Pat. No. 5,187,191, issued Feb. 16, 1993 to Otten et al, discloses physically stable aqueous pesticide compositions comprising water insoluble pesticides, polyoxyalkylene copolymer and water. Said polyoxyalkylene copolymer is heteric, i.e. it is comprised of EO and PO units, wherein some PO is incorporated into the EO blocks, e.g. (EO/PO) (PO) (EO/PO), in order to provide a liquid surfactant which is more easily used than a paste. 
     However, the use of these liquid heteric EO/PO block copolymers as adjuvants to increase the uptake of herbicides has not been described. Prior to the invention described herein, non-heteric EO/PO blocks with higher amounts of EO (i.e. &gt;30%) had not been previously tested in tank mixes because their physical form (paste) rendered them impractical for this application. 
     Applicants have now surprisingly discovered that liquid heteric EO/PO block copolymers, wherein the EO content is at least 30% by weight, are useful for enhancing the efficacy of herbicides and, thus, enhancing weed controlling activity. 
     SUMMARY 
     A method of enhancing the weed controlling activity of a broad spectrum herbicide comprising the administration of said broad-spectrum herbicide wherein a heteric EO/PO copolymer is used in conjunction with said broad-spectrum herbicide and said heteric EO/PO copolymer has surface active properties, and the formula: 
     
         Y[(EO, PO).sub.m (PO).sub.n (EO,PO).sub.m,H].sub.x 
    
     wherein Y is the nucleus of an organic reactive hydrogen compound having x reactive hydrogen atoms and up to 6 carbon atoms, x is an integer, EO is ethylene oxide, PO is a propylene oxide hydrophobe having an oxygen/carbon ratio of not more than 0.40, (EO,PO) represents a hydrophilic heteric block (a block of EO with PO molecules interspersed) having an oxygen/carbon ratio of more than 0.40, m, m&#39; and n are numbers such that the total molecular weight of said hydrophilic heteric block is from about 660 to 11,400, the total molecular weight of said PO hydrophobe is from about 1500 to 3600 and the total molecular weight of said copolymer ranges from about 2200 to 15,000, said copolymer being at least 30 weight percent hydrophilic (weight of the hydrophilic block) with said hydrophilic heteric block comprising from about 5 to 40 weight percent of PO; 
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a method of enhancing the systemic weed controlling activity of a broad spectrum herbicide comprising the administration of said broad-spectrum herbicide wherein a heteric EO/PO copolymer is used in conjunction with said broad-spectrum herbicide and said heteric EO/PO copolymer has surface active properties, and the formula: 
     
         Y[(EO,PO).sub.m (PO).sub.n (EO,PO).sub.m,H].sub.x 
    
     wherein Y is the nucleus of an organic reactive hydrogen compound having x reactive hydrogen atoms and up to 6 carbon atoms, x is an integer, EO is ethylene oxide, PO is a propylene oxide hydrophobe having an oxygen/carbon ratio of not more than 0.40,(EO,PO) represents a hydrophilic heteric block having an oxygen/carbon ratio of more than 0.40, m, m&#39; and n are numbers such that the total molecular weight of said hydrophilic heteric block is from about 660 to 11,400, the total molecular weight of said PO hydrophobe is from about 1500 to 3600 and the total molecular weight of said copolymer ranges from about 2,200 to 15,000, said copolymer being at least 30 weight percent hydrophilic with said hydrophilic heteric block comprising from about 5 to 40 weight percent of PO; 
     THE BROAD SPECTRUM HERBICIDE 
     Broad spectrum herbicides useful in the practice of the present invention include, but are not limited to, bentazone, (3-isopropyl-1H-2,1,3-benzothiadiazen-4(3H)-one-2,2-dioxide); quinchlorac, (3,7-dichloro-8-quinolinecarboxylic acid); acifluorfen, (sodium 5-[2-chloro-4-trifluoroethyl]phenoxy]2-nitrobenzoate); sethoxydim, (2-[1-(ethoxyimino)butyl]-5-[2 ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one); and glyphosate, (isopropylamine salt of N-(phosphono-methyl) glycine). Most preferred are quinchlorac and acifluorfen. 
     THE EO/PO POLYMERS 
     Liquid heteric EO/PO copolymers having surface active properties, useful in the practice of the present invention have the formula: 
     
         Y[(EO,PO).sub.m (PO).sub.n (EO,PO).sub.m,H].sub.x 
    
     wherein Y is the nucleus of an organic reactive hydrogen compound having x reactive hydrogen atoms and up to 6 carbon atoms, x is an integer, EO is ethylene oxide, PO is a propylene oxide hydrophobe having an oxygen/carbon ratio of not more than 0.40,(EO,PO) represents a hydrophilic heteric block having an oxygen/carbon ratio of more than 0.40, m,m&#39; and n are numbers such that the total molecular weight of said hydrophilic heteric block is from about 660 to 11,400, the total molecular weight of said PO hydrophobe is from about 1500 to 3600 and the total molecular weight of said copolymer ranges from about 2,200 to 15,000, said copolymer being at least 30 weight percent hydrophilic with said hydrophilic heteric block comprising from about 5 to 40 weight percent of PO; 
     The liquid heteric EO/PO polymers useful in the compositions of the present invention are described in detail in U.S. Pat. No. 5,187,191, incorporated by reference herein. 
     Preferred heteric EO/PO polymers useful in the compositions of the present invention are those with a PO block of at least 2400 molecular weight and between 30-60% EO. The heteric EO/PO polymers preferred in the practice of the present invention are commercially available as PLURAFLO® L860 (a 2400 molecular weight PO block with 60% EO, i.e., 60% by weight hydrophilic); PLURAFLO® L1030 (a 3000 molecular weight PO block with 30% EO, i.e., 30% by weight hydrophilic) and PLURAFLO® L1060 (a 3000 molecular weight PO block with 60% EO, i.e., 60% by weight hydrophilic), from the BASF Corporation, Mt. Olive, N.J. 
     TESTING OF THE COMPOSITIONS USEFUL IN THE METHOD OF THE PRESENT INVENTION 
     PLURAFLO L860, PLURAFLO L1030, and PLURAFLO L1060 were applied as surfactants with Poast® (sethoxydim--0.11 kg active ingredient/hectare (ai/ha), Basagran® (bentazone--0.56 kg active ingredient/hectare (ai/ha), Blazer® (acifluorfen--0.28 kg active ingredient/hectare (ai/ha), and Facet® (quinchlorac--0.14 kg active ingredient/hectare (ai/ha) (all products available from BASF Corporation, Mount Olive, N.J.). The PLURAFLO materials were added at 4.6, 2.3, 1.17 liter/hectare (1/ha). Treatments were applied in the laboratory with a laboratory track sprayer at 187 L/Ha and 276 Kpa (20 GPA, 40 psi). Bentazone and acifluorfen applications were made to soybeans with yellow nutsedge (Cyperus esculentus), prickly sida (Sida spinosa), velvet leaf (Abutilon theophrasti), redroot pigweed (Amaranthus retroflexus) and tall morning glories (ipomoea hederacea) and giant foxtail. Sethoxydim and quinchlorac were applied to soybeans, rice, barnyard grass (Echinochloa crus-galli), giant foxtail (Setaria faberii), large crabgrass (Digitaria sanguinalis), corn, shattercane (Sorghum vulgare), green sprangletop (Leptochloa dubia), broadleaf signalgrass (Bracharia platyphylla), and green foxtail (Setaria viridis), hempsesbania; and ladysthumb (Polygonum persicaria). In all trials the broadleaf weeds had four to six true leaves and grasses had three to four leaves. Weeds were generally larger in stature than plants grown outdoors having the same number of leaves. All plants were grown in an organic planting medium, Metro Mix 360 and fertilized with Osmocote slow release fertilizer. 
     The treatments described herein can also be prepared in the field as tank mixes according to methods known to those skilled in the art. 
     Tables 1 &amp; 2 show the results of the testing of the liquid heteric EO/PO polymers in enhancing quinchlorac and acifluorfen activity. 
     Specifically, in Table 1, the efficacy of the quinchlorac active as a weed controller is enhanced by the use of the EO/PO heteric copolymers, PLURAFLO L860, PLURAFLO L1030, PLURAFLO L1060, especially in controlling barnyard grass, when compared to the untreated control. Quinchlorac is a systemic rice herbicide and barnyard grass comprises up to 80% of the weed problems in the crops. Further, the use of these EO/PO heteric copolymers is more effective in enhancing barnyard grass control than a crop oil concentrate (COC). 
     The use of EO/PO heteric copolymers as adjuvants also enhances the weed killing effectiveness of quinchlorac on green foxtail and hempsesbania. 
     In Table 2, the efficacy of the contact herbicide acifluorfen as a weed controller is enhanced by the use of EO/PO heteric copolymers, particularly PLURAFLO L1030 and L1060, in tall morning glories and giant foxtail when compared to the untreated control. Further, the use of these EO/PO heteric copolymers is more effective in enhancing foxtail control than the COC. 
     Further, in both sets of data (Tables 1 &amp; 2), while the weeds are controlled, the rice is completely unharmed and soybean injury is minimal. The data also illustrate that the quinchlorac and acifluorfen can be applied at lower rates, i.e., the effectiveness at 1.17 1/ha can be just as effective or superior to applications at 2.3 1/ha and 4.6 1/ha. Thus, while the EO/PO heteric block copolymers enhance the systemic uptake or the contact area of these broad spectrum herbicides, there is no increase in injury to the cash crop. 
     
         TABLE 1
  - Effects of Surfactants on Quinchlorac Efficacy
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                                           TABLE 2                                 
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Effects of Surfactants on Acifluorfen Efficacy                            
                              RED-                                        
                          VEL-                                            
                              ROOT       YELLOW     GIANT                 
                                                         MORN-            
               SOY- COCKLE-                                               
                          VET PIG- PRICKLY                                
                                         NUTS- LADYS-                     
                                                    FOX- ING              
TREATMENT  L/HA                                                           
               BEANS                                                      
                    BUR   LEAF                                            
                              WEED SIDA  EDGE  THUMB                      
                                                    TAIL GLORIES          
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Untreated      0    0     0   0    0     0     0    0    0                
Acifluorfen    5    90    63  98   20    18    70   88   20               
Crop Oil Concentrate                                                      
               7    65    63  98   10    15    85   75   10               
PLURAFLO L860                                                             
           4.6 7    30    75  100  20    90    95   95   20               
           2.3 7    83    65  100  20    10    75   99   20               
           1.17                                                           
               7    75    75  100  15    10    75   100  15               
PLURAFLO L1030                                                            
           4.6 7    63    30  100  38    25    90   93   38               
           2.3 7    63    50  100  45    28    80   97   100              
           1.17                                                           
               7    100   100 100  35    20    90   90   95               
PLURAFLO L1060                                                            
           4.6 7    93    93  100  25    25    85   96   100              
           2.3 7    100   30  100  20    35    78   95   100              
           1.17                                                           
               7    63    45  100  20    25    75   98   100              
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