FUNGICIDES * 



Bordeaux mixture. ''■>'• '''• ''■'''• ''•'^' ''^ — The 4-4-50 fonuula 

 (4 pounds of copper sulfate crystals and 4 pounds of stone- 

 lime to 50 gallons of water) is one in conunon use. 



According to the common formulas several times as much 

 lime is used as is necessary to precipitate the copper. A 

 mixture used abroad, known as the Woburn mixture, calls for 

 a solution of copper sulfate with lime water and subsequent 

 dilution as contrasted with milk-of-lime used in the ordinary 

 Bordeaux mixture. According to Pickering ordinaiy Bor- 

 deaux mixture and the Woburn mixture, containing only 

 one-sixth as much copper, seem to be equivalent in fungicidal 

 action. 



To make large quantities of Bordeaux mixture, or small 

 amounts repeatedly, it is desirable to prepare separate con- 

 centrated stock solutions of copper sulfate and of lime. 

 These are made up at the rate of approximately one pound 

 of each to the gallon. In preparing a stock solution of 

 copper sulfate, a weighed amount of the commercial crystals, 

 "bluestone," is placed in a sack and suspended in water in a 

 barrel or other wooden vessel. The volume of the water 

 should equal in gallons the weight of the copper sulfate in 

 pounds. The solution, as formed, will flow to the bottom, 

 leaving comparatively fresh water in contact with the re- 

 maining crystals. Stirring partially defeats the purpose of 

 this method by increasing the concentration of copper 

 sulfate in the liquid in contact with the undissolved part. 

 If the copper sulfate is placed in the bottom of the barrel, it 

 will dissolve but slowly even with frequent stirring. When 

 dissolved, the solution should be made uniform by stirring. 



In preparing the stock solution of lime (the term in com- 

 * Prepared by W. A. Ruth. 

 440 



