COPPER SALTS 191 



Among the fungicides the two principal substances used are some 

 copper salt and some form of sulfur. 



Copper Sulfate. — Of the copper salts by far the most im- 

 portant is copper sulfate, which is used either in the form of a 

 plain solution on dormant trees or as Bordeaux mixture. This 

 plain solution has the advantage of being as easy to apply as 

 water, and where the grower does not Have to fight any scale 



FiQ. 87. — Spray injury on apples. Any copper salt is likely to cause this under certain con- 

 ditions of weather. 



insects, especially San Jose scale, it makes an excellent dormant 

 spray. It is usually applied at the strength of 3 or 4 pounds 

 of copper sulfate to 50 gallons of water. 



Bordeaux Mixture. — Where it can be used without danger, 

 Bordeaux mixture is still probably the most efficient fungicide 

 on the list. There seem to be two dangers from its use. On 

 apples, in certain seasons, especially where there are many rains 

 or a great deal of foggy weather, it may produce a russeting 

 of the surface of the fruit that injures its appearance and some- 

 times its keeping quality (Fig. 87). This damage is sometimes 

 very severe, in particularly bad cases even cracking the fruit 

 open. It affects some varieties more than others. In some 



