'204: A Copper Emulsion as a FiukjIcUIc 



Plot II. Unsprayed. 



Total 



Plot III. Sprayed twice with emulsion containing approximately 

 the equivalent of 0-8 per cent. CUSO4 . SHoO. 



Total 88| „ 



From these experiments, it would appear that the copper emulsion 

 at the lower strength (containing the equivalent of 0-4 per cent. 

 CUSO4 . 5H2O and 2 per cent, soft soap) is an efficient preventive 

 against blight when used on potato foliage, and when carefully prepared 

 with rain water it can be apj)lied without difficulty. Further experi- 

 ments^ however, are necessary, particularly with respect to its preparation 

 when only hard water is available, before it can be generally recom- 

 mended as a practical spray fluid. Although this fluid was originally 

 prepared and examined from another point of view, on account of the 

 small amount of copper used in its preparation and of its fungicidal 

 value, it is worth while trying to overcome the difficulty experienced in 

 making the emulsion under practical conditions. From an economic 

 point of view, the large amount of soap required is partly compensated 

 for by the small amount of copper necessary and the property of 

 spreading over the foliage which soap gives to the fluid. 



The fungicidal value of the emulsion, which contains much less 

 copper than Burgundy or Bordeaux mixtures as commonly used, is 

 probably due, in part, to the fact that the particles, owing to their 

 extreme fineness, must come in intimate contact with the leaf 

 surface and to the adhesive nature of the copper compound which 

 it contains. 



Summari/. An emulsion containing the equivalent of 0- J per cent, 

 copper sulphate (CUSO4 . SHgO) can be made by mixing solutions of 

 copper sulphate and soft soap, and this exhibits preventive action 

 against the attacks of the potato blight fungus. 



