INSECTS AND tfUKGl. 267 



moulds, mildews, rusts, etc., but not until within a few 

 years has it been largely used for the purpose of destroying 

 these growths on cultivated trees, plants, and farm crops. 

 The form in which it is most used is that of copper sulphate 

 or blue vitriol, in which the copper is united with sulphuric 

 acid and is in the form of blue crystals. In this form it is 

 very soluble and very injurious to the growing parts of 

 plants unless used in a very dilute form; 1 part of copper 

 sulphate to 1500 or 2000 parts of water being as concen- 

 trated as it can be used without injury. In this form it is 

 quickly washed off by heavy rains and to prevent this lime 

 is used with it, forming what is known as the 



BORDEAUX MIXTURE. Formula: 4 Ibs. copper sul- 

 phate, 4 Ibs. caustic (unslaked) lime, and 50 gallons water. 



By combining the copper and lime it is found that the 

 copper sulphate may be used more freery and with less injury 

 than if used alone, and that it will adhere a long time to 

 the foliage. To make the Bordeaux mixture, dissolve the 

 copper in hot water (or if placed in a coarse sack or basket 

 and suspended in a tub of cold water it will dissolve in two 

 or three hours, while if put in cold water on the bottom 

 of a tub or vessel it remains undissolved for a long time). 

 Then in a separate tub slake the lime thoroughly and when 

 both are cold pour the two together, stirring constantly. 

 Dilute with water to make 50 gals, of liquid. In this 

 form it is more difficult to apply than a simple solution, 

 but the lime causes it to adhere for a long time and spray- 

 ing need not be so frequently done. Before using, the 

 mixture should be strained through a burlap or fine wire 

 strainer to take out the coarse particles of lime. The 

 Vermorel or some other adjustable nozzle that will throw 

 a very fine spray or mist must be used to distribute the 



