27 



With good lime it only needs about one pound to act on all the cop- 

 per; the excess given, three pounds, covers all danger which might arise 

 from the use of a poor article. A large excess of lime is a disadvantage, — 

 it causes the Bordeaux mixture to exert a slow fungicidal action, it is apt 

 to cause the machinery to clog and to cause an uneven application, and 

 the particles of lime offering more resistance to rain, will cause the mix- 

 ture to be more rapidly washed from the trees. It may be an advantage, 

 however, in a very wet season, by causing the Bordeaux to retain its 

 efficiency longer and by allowing less injury to be done to foliage. Orch- 

 ardists are inclined to use a less proportion of lime, and the following 

 formula is recommended : 



CuS0 4 (crystallized copper sulphate) 6 pounds. 



CaO (quick lime) 4 



Water 40 gallons. 



As both copper sulphate and lime dissolve and slake, respectively, 

 much quicker in hot water than cold, it is better to use heated water in 

 order to save time. The very best lime obtainable is used, and if freshly 

 burned, all the better. In slaking do not use an excess of water, but just 

 enough to keep the lime moist. When the action is completed enough 

 water is added to make a thin whitewash and then the whole is strained 

 through coarse sacking to remove any lumps which would clog the nozzle 

 of the spray pump. This done, enough water is added to make the volume 

 up to one-half of what the final mixture will amount to. The copper 

 sulphate solution is diluted to the same extent. The two are now mixed, 

 the operation being best performed by two men, each with a bucket, one 

 handling the lime and the other the copper sulphate. They are poured 

 into the spray tank, two bucketsful at a time, until the whole is brought 

 together. In this way a precipitate is obtained which will remain in 

 suspension with only occasional agitation. If mixing is done before 

 dilution, a very coarse precipitate is formed which settles rapidly to the 

 bottom of the spray tank and requires almost constant stirring. 



If large quantities of spray mixture are eoing to be used, it is an 

 excellent plan to make up "stock" solutions of the copper and lime. This 

 can be done by dissolving, say, one pound of copper sulphate in each 

 gallon of water and making up a barrel full' of it. Each gallon of the 

 solution taken then represents one pound of the bluestone. The salt can 

 be conveniently dissolved by filling the barrel with water and then sus- 

 pending it therein, enclosed in a canvas sack. The lime can be handled 

 in the same way, being sure, of course, that the contents of the barrel 

 are thoroughly stirred up before dipping out any portion. Keep the 

 barrels covered when not in use. 



Precautions to be Used in Making. Before Bordeaux mixture is 

 sprayed, it is absolutely necessary that all copper should be in the form 

 of the sky-blue precipitate, i.e., enough lime must be used to act on all 

 the bluestone. Formulae advocated by the experiment stations always 

 contain enough lime to precipitate all the copper, but it may sometimes 



