Orchard Pests and their Control 389 



strained through a strainer with openings the size of a pinhead. 

 This prevents the clogging of the nozzles with any of the coarse 

 material left after slaking. The copper sulfate should be dis- 

 solved in warm water if wanted for immediate use. It may be 

 dissolved in a considerable quantity of cold water by suspending 

 it in a sack just beneath the surface. If to be used in large 

 quantities, it is well to make up a stock solution by dissolving 

 fifty pounds in twenty-five gallons of water. Keep well covered 

 to prevent evaporation. Two gallons of this solution contain the 

 four pounds of copper sulfate called for in Formula A, or one 

 gallon contains the two pounds called for in Formula B. The re- 

 quired amount of this solution should be diluted to at least thirty 

 gallons before the lime water is added. The lime may be slaked 

 in large quantities, in which condition it will keep well all summer, 

 and the amount of lime water or paste required may be deter- 

 mined by a chemical test. 



For this test potassium ferrocyanide may be secured of any 

 druggist and prepared for use by dissolving in ten times its bulk 

 of water. A quantity of lime water is then added to the diluted 

 copper solution, stirred well, and a drop of cyanide dropped upon 

 the surface. If it gives a reddish brown color to the mixture, 

 more lime must be added and the test repeated until no reaction 

 occurs. This indicates that all harmful acids of the copper 

 have been neutralized, and the mixture is ready for use. Red 

 litmus paper may be used and lime added until the solution turns 

 the paper to a blue color. 



Bordeaux mixture is used in combating plant diseases. ] 

 has no effect on insects, except that it acts as a repellent. It 

 has been used successfully in this way in ridding potatoes and 

 other vegetables of flea-beetles. 



Bordeaux mixture deteriorates rapidly and should be used as 

 soon as prepared. While being sprayed it requires constant 

 stirring. In the preparation of the mixture no metal vessels or 

 tools other than copper or brass should be used. Apply to apple 

 and to pear trees only on bright days, otherwise the mixture is 

 likely to injure both fruit and foliage. 



Whitewash. Whitewash is much used in California to protect 



