INSECTS, DISEASES, AND INJURIES 165 



be covered with sheet tin, zinc, or iron, but the practice is not 

 to be recommended. 



4. Fungicides 



Spraying or dusting are of value in the control of leaf 

 diseases in the orchard and in the field, but very little informa- 

 tion is available concerning the application of these measures 

 to ornamental trees and shrubs. There seems to be no reason, 

 however, why they should not be effective. Fungicides should 

 be applied before rainy periods and before infection has taken 

 place (except in the case of surface fungi such as the mildews), 

 for they are generally preventive and not curative agencies. 

 The three commonest fungicides are bordeaux mixture, lime- 

 sulfur, and sulfur. 



Bordeaux mixture consists of a mixture of copper sulfate 

 (blue vitriol) and milk of lime, the active principle being the 

 metallic copper. A stock solution of copper sulfate is made by 

 dissolving the required number of pounds of crystals in as 

 many gallons of water. This is most easily accomplished by 

 placing the crystals in a bag and suspending this just below 

 the surface of the water. A wooden container should be used 

 for this solution, as it rapidly corrodes metallic surfaces. 

 The milk of lime is prepared by slaking stone lime and gradually 

 adding water until a thick smooth paste is obtained. Sufficient 

 water is then added to make the number of gallons equal the 

 number of pounds of lime. The spray is used in various 

 strengths, 4-4-50 being the average. This formula signifies 

 that four pounds of copper sulfate, four pounds of lime, and 

 fifty gallons of water make up the mixture. In preparing fifty 

 gallons at this strength, four gallons of the stock copper sulfate 

 solution should be placed in the tank and then thirty-two 

 gallons of water added. After this has been done, the four 



