Plant growth inhibiting composition
BACKGROUND OF THE INVENTION 
     The present invention relates to a plant growth regulating composition, and particularly to a plant growth regulating composition which comprises the choline salt of 6-hydroxy-3(2H)-pyridazinone (hereinafter referred to as MH) and, as adjuvants, a polyoxyethylene oleyl ether and a triethanolamine alkylsulfate. 
     Heretofore, various salts of MH have widely been used as sucker (axillary bud) inhibitors for tobacco plants, sprouting inhibitors for onions or Irish potatoes in storage, or growth regulating agents for wild weeds. However, such conventional salts of MH do not have sufficient penetration and transferability, and accordingly do not provide adequate effectiveness. 
     Accordingly, it has long been desired to develop an MH composition which has low toxicity, provides easy handling, has good penetration and good transferability and provides adequate effectiveness under all natural conditions. 
     SUMMARY OF THE INVENTION 
     Under the circumstances, the present inventors have conducted an extensive research on it, and as a result, have found that a composition prepared by mixing the choline salt of MH with a polyoxyethylene oleyl ether and a triethanolamine alkyl sulfate as adjuvants, has low toxicity, lets MH be absorbed from the leaf surfaces of plant in a short period of time thereby improving its effectiveness, whereby the amount of use can be reduced and the rain resistance can be improved. This invention has been made on the basis of the above discovery. 
     In one aspect of this invention, there is provided a plant growth regulating composition which comprises the choline salt of 6-hydroxy-3(2H)-pyridazinone and as adjuvants, polyoxyethylene oleyl ether and triethanolamine alkylsulfate. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     Choline of the choline salt of MH constituting the main effective component of the plant growth regulating composition of the present invention, is widely distributed in animal or plant bodies and has little toxicity and a strong affinity to plants thus providing a merit that the penetration and transferability is good. Furthermore, choline is industrially readily available and therefore economical. 
     The polyoxyethylene oleyl ether to be used as an adjuvant is preferably an addition product containing 2 to 35 moles of oxyethylene. As the triethanolamine alkyl sulfate, the one having an alkyl group of 8 to 18 carbon atoms is preferred, and particularly preferred is triethanolamine laurylsulfate. The ratio of the polyoxyethylene oleyl ether to the triethanolamine alkylsulfate is preferably within a range of 1:1 to 1:0.5 (by weight). The ratio of the choline salt of MH to the adjuvants is preferably within a range of 1.36:1 to 5.2:1 (by weight). 
     According to the present invention, unexpectedly high effectiveness is obtainable by the combination of the choline salt of MH and the above-mentioned adjuvants. It is not possible to improve the effectiveness of the MH salt by using, instead of the polyoxyethylene oleyl ether, a well-known non-ionic surface active agent such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether or polyoxyethylene fatty acid ester, or by using, instead of the triethanolamine alkylsulfate, a well-known anionic surface active agent such as an alkyl benzene sulfonate, an alkyl sulfosuccinate or an ammonium salt of laurylsulfuric acid. 
     The plant growth regulating composition of the present invention may be prepared by mixing or dissolving, for example, in water the choline salt of MH and the adjuvants in the above-mentioned ratios. It is possible to add a hydrophilic solvent, for instance, a C 1  -C 4  lower alcohol such as methanol, ethanol or isopropanol, or C 1  -C 4  alkylether of a glycol such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, ethyl carbitol, or butyl carbitol; a turbidity inhibitor effective at a low temperature such as urea, glycerin, polyethylene glycol (molecular weight of up to 1000) or polypropylene glycol (molecular weight of up to 1000); or a defoaming agent such as methylsilicon, alkyl phosphate, or fatty acid. 
     It is preferred to prepare the composition of the present invention in a form of a concentrated solution containing, for instance, 30 to 55% by weight of the choline salt of MH and to dilute it for use with water, for example, 30 to 150 times (preferably 60 to 120 times) in the case of tobacco leaves or 60 to 200 times (preferably 60 to 150 times) in the case of eradication of weeds. 
    
    
     Now, the invention will be described with reference to the following examples. 
     EXAMPLE 1 
     To 88 parts by weight of an aqueous solution of the choline salt of MH (hereinafter referred to as C-MH aqueous solution), 12 parts by weight of the adjuvants were mixed to obtain a plant growth regulating composition. The C-MH aqueous solution contained 30.5% of MH, 58.8% of the choline salt of MH and the rest being water. 
     Said composition was diluted 300 times and applied to tobacco leaves (Virginia 115) cultured in the Wagner pot of 10 ares×1/50,000 after topping in early flower stage, at a rate of 5 ml per plant. The experiment was made with 4 series per section, and after expiration of 14 days, an average weight of suckers per plant was measured to determine the inhibition rate. The inhibition rate was calculated in accordance with the following formula. The results obtained are shown in Table 1. The numerals (p) in the brackets in the column for the adjuvants represent moles of the polyoxyethylene addition. Further, a comparison is made with compositions prepared by other than the present invention. ##EQU1## 
     
                                           TABLE 1                                 
__________________________________________________________________________
       Composition               MH concentra-                            
       Aqueous MH                tion at the                              
                                         Average                          
       solution                                                           
              Adjuvants                                                   
                    Adjuvants (kinds and                                  
                                 time of weight of                        
                                              Inhibition                  
       (parts by                                                          
              (parts by                                                   
                    mixing proportions)                                   
                                 application                              
                                         suckers                          
                                              rates                       
       weight)                                                            
              weight)                                                     
                    [wt %]       [%]     [g]  [%]                         
__________________________________________________________________________
Products                                                                  
        88    12    Polyoxyethylene (-p = 8)                              
                                 0.089   1.35 83.5                        
of the              oleyl ether/trietha-                                  
present             nolamine laurylsulfate/                               
invention           methyl cellosolve/water                               
                    = 21:21:16:42                                         
        88    12    Polyoxyethylene (-p = 20)                             
                                 0.089   1.13 86.2                        
                    oleyl ether/triethanol-                               
                    amine laurylsulfate/                                  
                    methyl cellosolve/                                    
                    water = 30:23:12:35                                   
Comparative                                                               
       100    0     Not added    0.1     2.1  74.2                        
products                                                                  
       100    0     Not added    0.1     2.7  66.9                        
       (A-MH)                                                             
       100    0     Not added    0.1     3.4  58.3                        
       (K-HM)                                                             
Con-   No Treatment              --      8.16 --                          
trol                                                                      
__________________________________________________________________________
 (Note)                                                                   
 In the above Table, AMH represents the diethanolamine salt of MH (an     
 aqueous solution containing 30.5% of MH), KMH represents the potassium   
 salt of MH (an aqueous solution containing 30.5% of MH) and an aqueous MH
 solution without notes represents an aqueous CMH solution.               
 
    
     It is apparent from Table 1 that the compositions of the present invention exhibit superior efficacy of sucker control to C-MH, A-MH, or K-MH, using no adjuvants, and that C-MH has a superior penetrability than A-MH or K-MH. 
     EXAMPLE 2 
     The following compositions were prepared in a manner similar to Example 1 and sucker inhibition experiments were carried out with respect to tobacco leaves. 
     The results obtained are shown in Table 2. 
     
                                           TABLE 2                                 
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Composition                                                               
Aqueous                          MH concentra-                            
C-MH                             tion at the                              
                                         Average                          
                                              Sucker                      
solution   Adjuvants                                                      
                 Adjuvants (compositions                                  
                                 time of weight of                        
                                              inhibition                  
(parts by  (parts by                                                      
                 and mixing proportions)                                  
                                 application                              
                                         suckers                          
                                              rates                       
weight)    weight)                                                        
                 [wt %]          [%]     [g]  [%]                         
__________________________________________________________________________
Products                                                                  
      80   20    Polyoxyethylene (-p = 9) oleyl                           
                                 0.08    1.7  80                          
of the           ether/triethanolamine                                    
present          laurylsulfate/methanol/water                             
invention        = 15:24:25:36                                            
      80   20    Polyoxyethylene (-p = 20) oleyl                          
                                 0.08    1.7  80                          
                 ether/triethanolamine                                    
                 laurylsulfate/methanol/water                             
                 = 30:20:20:30                                            
      80   20    Polyoxyethylene (-p = 30) oleyl                          
                                 0.08    1.3  83                          
                 ether/triethanolamine                                    
                 laurylsulfate/methanol/water                             
                 = 30:20:20:30                                            
Compara-                                                                  
      80    0    Not added       0.08    2.7  65                          
tive  100   0    Not added       0.1     2.3  70.0                        
products                                                                  
Con-  No treatment               --      7.7  --                          
trol                                                                      
__________________________________________________________________________
 
    
     EXAMPLE 3 
     The following compositions were prepared in a manner similar to Example 1, and sucker inhibition experiments were carried out with respect to tobacco leaves. The results obtained are shown in Table 3. 
     
                                           TABLE 3                                 
__________________________________________________________________________
       Composition                                                        
       Aqueous                   MH concentra-                            
       MH                        tion at the                              
                                         Average                          
                                              Sucker                      
       solution                                                           
            Adjuvant                                                      
                 Adjuvants (compositions                                  
                                 time of weight of                        
                                              inhibition                  
       (parts by                                                          
            (parts by                                                     
                 and mixing proportions)                                  
                                 application                              
                                         suckers                          
                                              rates                       
       weight)                                                            
            weight)                                                       
                 [wt %]          [%]     [g]  [%]                         
__________________________________________________________________________
Products                                                                  
       70   30   Polyoxyethylene (-p = 9) oleyl                           
                                 0.07    1.42 79.0                        
of the           ether/triethanolamine                                    
present          laurylsulfate/methanol/water                             
invention        = 23:21:24:32                                            
       70   30   Polyoxyethylene (-p = 20) oleyl                          
                                 0.07    1.11 83.6                        
                 ether/triethanolamine                                    
                 laurylsulfate/methanol/water                             
                 = 33:18:21:28                                            
       70   30   Polyoxyethylene (-p = 30) oleyl                          
                                 0.07    1.45 78.5                        
                 ether/triethanolamine                                    
                 laurylsulfate/methanol/water                             
                 = 33:18:21:28                                            
Comparative                                                               
       70   30   Polyoxyethylene (-p = 20) oleyl                          
                                 0.07    3.20 55.3                        
products                                                                  
       (K-MH)    ether/polyoxyethylene (-p = 20)                          
                 nonyl phenyl sodium sulfate/                             
                 methanol/water = 33:18:21:28                             
       70   30   Polyoxyethylene (-p = 20) oleyl                          
                                 0.07    2.98 54.8                        
       (K-MH)    ether/triethanolamine                                    
                 laurylsulfate/methanol/water                             
                 = 33:18:21:28                                            
       70   30   Polyoxyethylene (-p = 20) oleyl                          
                                 0.07    2.18 70.1                        
                 ether/polyoxyethylene (-p = 20)                          
                 nonyl phenyl sodium sulfate/                             
                 methanol/water = 33:18:21:28                             
       70   0    Not added       0.07    2.59 61.7                        
       100  0    Not added       0.1     2.11 68.8                        
Con-   No treatment              --      6.75 --                          
trol                                                                      
__________________________________________________________________________
 (Note)                                                                   
 In the above Table, KMH represents the potassium salt of MH (an aqueous  
 solution containing 30.5% of MH) and an aqueous MH solution without notes
 represents CMH aqueous solution.                                         
 
    
     EXAMPLE 4 
     In a manner similar to Example 1, a homogeneous liquid composition was obtained by adding 33 parts of the adjuvants of the present invention to 67 parts of C-MH aqueous solution. This composition was diluted 60 times and applied to tobacco leaves (Virginia species: Va-115) cultivated in an agricultural field after topping in early flower stage at a rate of 20 ml per plant. The experiment was carried out with 4 series per section, and after expiration of 20 days the evaluation was made. A few compositions other than those of the present invention were tested for the purpose of comparison. The results obtained are shown in Table 4. 
     
                                           TABLE 4                                 
__________________________________________________________________________
       Compositions                                                       
       Aqueous                    MH concentra-                           
                                          Suckers                         
       MH                         tion at the                             
                                          inhibi-                         
       solution                                                           
            Adjuvants                                                     
                  Adjuvants (kinds and                                    
                                  time of tion                            
       (parts by                                                          
            (parts by                                                     
                  mixing proportions)                                     
                                  application                             
                                          rates                           
       weight)                                                            
            weight)                                                       
                  [wt %]          [%]     [%]  Toxicity                   
__________________________________________________________________________
Product                                                                   
       67   33    Polyoxyethylene (-p = 8) oleyl                          
                                  0.34    98.4 None                       
of the            ether/triethanolamine                                   
present           laurylsulfate/methanol/water                            
invention         = 23:22:23:32                                           
       67   33    Polyoxyethylene (-p = 20) oleyl                         
                                  0.34    98.7 None                       
                  ether/triethanolamine                                   
                  laurylsulfate/methanol/water                            
                  = 33:18:21:28                                           
Comparative                                                               
       67   33    Polyoxyethylene (-p = 8) oleyl                          
                                  0.34    85.3 None                       
product 1         ether/methanol/water                                    
                  = 34:21:45                                              
Comparative                                                               
       67   33    Triethanolamine laurylsul-                              
                                  0.34    83.5 None                       
product 2         fate/methanol/water                                     
                  = 23:21:56                                              
Comparative                                                               
       99   1     Polyoxyethylene alkylphenol                             
                                  0.5     98.0 None                       
product 3                                                                 
       (A-MH)     ether/polyoxyethylene                                   
(sold on the      dodecyl ether/sodium                                    
market)           laurylsulfate = 20:60:20                                
__________________________________________________________________________
 (Note)                                                                   
 In the above Table, AMH represents the diethanolamine salt of MH (an     
 aqueous solution containing 30.5% of MH) and an aqueous MH solution      
 without notes means an aqueous CMH solution.                             
 
    
     It is apparent from Table 4 that the compositions of the present invention have superior efficacy of sucker control to the conventional A-MH product sold on the market although the effective concentration of MH was lower in the compositions of this invention, and that an synergistic effect is obtainable by the combination of polyoxyethylene oleyl ether and triethanolamine laurylsulfate. 
     EXAMPLE 5 
     A homogeneous liquid composition was obtained by mixing 70 parts of an aqueous C-MH solution and 30 parts of the adjuvants of the present invention in a manner similar to Example 1. The composition was diluted 60 times and applied to Dandelion Blowballs cultured for 50 days, after their sprouting in the Wagner pot of 10 ares×1/50,000, at a rate of 2 ml per plant and the MH absorption rates in the Dandelion Blowballs were measured after 2, 6, 24 and 30 hours. 
     The absorption rates were calculated by the following formula. ##EQU2## 
     The MH amounts attached to leaves and stems were obtained by washing the test samples with an aqueous solution containing 1% of sodium hydroxide and subjecting it to a quantitative analysis. 
     The results obtained are shown in Table 5. 
     
                                           TABLE 5                                 
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       Compositions                                                       
       Aqueous                               MH concen-                   
       MH                                    tration at                   
       solution                                                           
            Adjuvants                                                     
                  Adjuvant (kinds and                                     
                              MH absorption rates (%)                     
                                             the time of                  
       (parts by                                                          
            (parts by                                                     
                  mixing proportions)                                     
                              time (hr)      application                  
       weight)                                                            
            weight)                                                       
                  [wt %]      0.5                                         
                                 2  6  24 30 (%)                          
__________________________________________________________________________
Products                                                                  
       70   30    Polyoxyethylene (-p = 8)                                
                              15 46 79 91.2                               
                                           92                             
                                             0.35                         
of the            oleyl ether/triethanol-                                 
present           amine laurylsulfate/                                    
invention         methanol/water =                                        
                  23:22:23:32                                             
Comparative                                                               
       100  0     Not added   5.2                                         
                                 21 35 63 70.2                            
                                             0.5                          
products                                                                  
       Standard A-MH          10.1                                        
                                 30.3                                     
                                    47 69.7                               
                                          79.3                            
                                             0.5                          
__________________________________________________________________________
 (Note)                                                                   
 In the above Table, Standard AMH represents the same product as          
 Comparative product 3 in Table 4 and, without any specific indication, an
 aqueous CMH solution is meant.                                           
 
    
     It is apparent from Table 5 that the compositions of the present invention give very high absorption rates. 
     EXAMPLE 6 
     A homogeneous liquid composition was obtained by mixing 83 parts of C-MH and 17 parts of the adjuvants of the present invention in a manner similar to Example 1. The composition was diluted 60 times and applied to Horse Weed cultured to a height of 36 cm in an agricultural field, at a rate of 72 liters per 10 ares at the stems and leaves, and portions above the earth were cut off after 2, 4, 8, 24 and 96 hours after the treatment. Upon expiration of 30 days, the heights of newly-grown weed were measured to determine the inhibition rate. The inhibition rate was calculated by the following formula. ##EQU3## 
     
                                           TABLE 6                                 
__________________________________________________________________________
       Compositions                  Inhibition rates (%)                 
       Aqueous                  MH   Time for cutting off                 
       MH                       amounts                                   
                                     the portions above the               
       solution                                                           
            Adjuvants                                                     
                  Adjuvants (kinds and                                    
                                per  earth after the                      
       (parts by                                                          
            (parts by                                                     
                  mixing proportions)                                     
                                10 ares                                   
                                     application (hr)                     
       weight)                                                            
            weight)                                                       
                  [wt %]        (g)  2 4  8  24 96                        
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Product                                                                   
       83   17    Polyoxyethylene (-p = 20)                               
                                300  75                                   
                                       81.3                               
                                          87.5                            
                                             89.3                         
                                                98.3                      
of the            oleyl ether/triethanolamine                             
present           laurylsulfate/methanol/                                 
invention         water = 22:23:20:35                                     
Comparative                                                               
       Standard A-MH            360  43                                   
                                       65.2                               
                                          69.7                            
                                             78.3                         
                                                90.6                      
products                                                                  
       Inhibition rate upon expiration of 30 days after                   
                                300  26%                                  
       application of the above product of the present                    
       invention without cutting off the portions above                   
       the earth.                                                         
__________________________________________________________________________
 (Note)                                                                   
 In the above Table, Standard AMH represents the same product as          
 Comparative product 3 in Table 4.                                        
 
    
     It is apparent from Table 6 that the composition of the present invention has good penetration and transferability into plants. Further, it is seen that a higher inhibition effectiveness is obtainable when the portions above the earth are cut off after the application of the composition and after the absorption of MH. 
     EXAMPLE 7 
     The composition of the present invention prepared in a manner similar to Example 4, was applied to onions and Irish potatoes cultured on earth in a green house, and the amounts of MH residue in the bulbs and tuberous roots were measured. The composition of the present invention was diluted 100 times with water, and applied at a rate of 80 liters per 10 ares. Upon expiration of 3 weeks after the application, the tubers and tuberous roots were dug out and the MH contents were measured. 
     The results are shown in Table 7. 
     
                                           TABLE 7                                 
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       Compositions                                                       
       Aqueous MH                  MH amount                              
       solution                                                           
              Adjuvants                                                   
                    Adjuvants (kinds and                                  
                                   per 10 ares                            
                                           MH contents (ppm)              
       (parts by                                                          
              (parts by                                                   
                    mixing proportions)                                   
                                   and concentra-                         
                                           Irish                          
       weight)                                                            
              weight)                                                     
                    [wt %]         tion (%)                               
                                           potatoes                       
                                                Onions                    
__________________________________________________________________________
Product                                                                   
       67     33    Polyoxyethylene (-p = 8) oleyl                        
                                   160 g   21.3 10.3                      
of the              ether/triethanolamine                                 
present             laurylsulfate/methanol/                               
                                   0.2%                                   
invention           water = 23:22:23:32                                   
Comparative                                                               
       Standard A-MH               240 g   18.7 8.9                       
product                            0.3%                                   
__________________________________________________________________________
 (Note)                                                                   
 In the above table, Standard AMH represents the same product as          
 Comparative product 3 in Table 4.                                        
 
    
     It is apparent from Table 7 that in spite of the fact that the amount of application of the composition of the present invention was less than that of A-MH, the composition of the present invention was absorbed in a greater amount thus indicating superior penetration and transferability. 
     EXAMPLE 8 
     1.6 kg of the composition of the present invention prepared by Example 1 was diluted 50 times by water and applied to leaves of Kudzu-vine grown at road sides at a rate of 80 liters per 10 ares (October 15) and the regeneration state was investigated next spring (May 12). For the purpose of comparison, 2 kg of Standard A-MH was diluted 40 times and applied at a rate of 80 liters per 10 ares. 
     The results obtained are shown in Table 8. 
     
                                           TABLE 8                                 
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       Compositions                                                       
       Aqueous                                 Amounts (g)                
       MH                    Covering                                     
                                    Number of  and con-                   
       solution                                                           
            Adjuvants                                                     
                  Adjuvants (kinds and                                    
                             rate of the                                  
                                    regenerated                           
                                           Length                         
                                               centrations                
       (parts by                                                          
            (parts by                                                     
                  mixing proportions)                                     
                             regenerated                                  
                                    Kudzu-vines                           
                                           of new                         
                                               (%) of MH                  
       weight)                                                            
            weight)                                                       
                  [wt %]     Kudzu-vine*                                  
                                    per m.sup.2                           
                                           vines                          
                                               per 10 ares                
__________________________________________________________________________
Product                                                                   
       88   12    Polyoxyethylene                                         
                             1      0.3    9.5 422 (g)                    
of the            (-p = 20) oleyl ether/       0.52 (%)                   
present           triethanolamine                                         
invention         laurylsulfate/methyl                                    
                  cellosolve/water =                                      
                  30:23:12:35                                             
Comparative                                                               
       Standard A-MH         1.5    0.5    10.3                           
                                               600 (g)                    
product                                        0.75 (%)                   
Con-   No application area   100    14.3   213 --                         
trol                                                                      
__________________________________________________________________________
 *Proportion (%) of the earth surface covered by the leaves of Kudzuvines.
 (Note)                                                                   
 In the above table, Standard AMH represents the same product as          
 Comparative product 3 in Table 4.