PREPARATION OF THE COPPER SPRAYS. 151 



growers, but the ofeneral principles involved remain the same. As a 

 common example, the manner of preparinj^- the o-pound formula \vill 

 be described: In a -15 or 6<> gallon })arrel place 5 pounds of copper sul- 

 phate and add 10 or 12 gallons of water. Pound and stir the copper 

 suipliate until wholly dissolved. In a half barrid slake 5 pounds of 

 quicklime and reduce with 10 or 12 gallons of water. Strain the milk 

 of lime into the copper solution, stir thoroughly, and add suJlicient 

 water to make 45 gallons in all. The copper and lime solutions should 

 both bo cold when united. When the water is added and the whole is 

 well stirred the spray is ready to be applied. 



For the manner of preparing the stock solution of copper sidphate to 

 be used for Bordeaux mixture the reader is referred to pages 148 and 

 149, where full instructions will ]»e found. In respect to the addition of 

 lime to the copper solution, it may be said that tli(> milk of lime result- 

 ing from the slaking of 2 pounds of good quicklime in (j or 8 gallons 

 of water is sufficient to neutralize a solution of 3 pounds of copper 

 sulphate. Larger amounts of copper should receive larger amounts 

 of lime in proportion. In case foliage is to be treated, however, it is 

 well before using the mixture to test it according to one of the methods 

 given, ^ or to bring the weight of quicklime used to three-fourths, 



until April, when unprotected buds swelled perceptibly during warm days late in 

 February and early in March; whitened buds blossomed three to six days later than 

 unprotected buds; 80 per cent of whitened buds passed the winter safely, and only 

 20 per cent of unwhitened buds passed the winter unharmed. These facts point to 

 those sprays having large amounts of lime as most valuable in protecting buds, and 

 they should be considered in those sections of the coimtry where the buds are liable 

 to winter injury. A fall spraying may also be a decided advantage in such situations 

 in addition to the early spring spraying for curl. 



See also on this subject the January niunber of the Canadian Horticulturist, 1899, 

 pp. 18-20. 



^ There are at present several convenient methods practiced in making Bordeaux 

 mixture to determine if enough lime has been added to the copper sulphate solution 

 to prevent injury when the mixture is applied to foliage. We adapt the following 

 two tests from Farmers' Bulletin No. 38 of this Department, p. 7: (a) After the 

 milk of lime and copper sulphate solutions have been united and thoroughly stirred, 

 hold the blade of a penknife in the mixture for at least a minute. If metallic copper 

 forms on the blade or the polished steel surface assumes the color of copper plate, 

 the mixture is still corrosive and should receive more milk of lime. If the blade 

 remains michanged, the mixture may be safely applied to most foliage under favor- 

 able weather conditions, (b) Pour some of the mixture into a saucer, hold between 

 the eyes and the light, and breathe gently upon it for at least half a minute. If the 

 mixture is properly made, a thin pellicle, looking like oil on water, will begin to 

 form on the surface. If no pellicle forms, more milk of lime should be added. A third 

 test (c) may be made with a 20 per cent solution of ferrocyanide of potassium : After 

 the milk of lime is added to the copper sulphate solution, and the whole is thoroughly 

 stirred, dip up a coffee cup full and add to this a few drops of the ferrocyanide of potas- 

 sium solution. Allow the cup to stand a few minutes and then pour off the mixture 

 carefully. If a red precij^itate is found at the liottom of the cup, the mixture requires 

 more milk of lime, which should be added until no such red precipitate is formed 

 when the test is repeated. 



