393 



Plant Sanitation. 



convenient place to do the work. The platform can be arranged with a roadway on 

 its upper side so that the lime and bluestone can be delivered there, while the spray 

 tank is being filled from the lower side. 



The Water Supply. — A water supply of some sort is necessary; a tank filled by 

 a windmill pump and elevated so as to be a few feet above the dilution tanks, or an 

 iron pipe with a spigot may be placed over each tank. Each dilution tank should 

 hold half the quantity it is desired to make up at one time— that is, if a 200-gallon 

 spray tank is to be filled the dilution tanks must hold about 100 gallons each. There 

 is no objection to adding a few extra gallons of water, but it is better to have the 

 tanks hold just the right quantity. 



Methods of Mixing the Solutions. — Either of two methods of mixing can be 

 employed : one in which the spray material is conducted directly from the dilution 

 tanks into the spray tank and actually mixed in this tank ; the other in which a 

 mixing tank sits just below the dilution tanks and from which the spray, after being 

 mixed up, is conducted by gravity into the spray tank. In certain ways the latter is 

 more convenient than mixing directly iuto the tank, but unless the operations are 

 somewhat extensive it will hardly justify the extra expense. In very large oper- 

 ations, however, a separate mixing tank is recommended— or perhaps even two of 

 them side by side — so that batches of the mixture can be kept on hand for a few 

 moments awaiting the spray wagons. 



TESTING BORDEAUX MIXTURE. 



When Bordeaux mixture is properly prepared it is of a brilliant sky-blue 

 colour. If the lime is air-slaked or otherwise inferior in quality, resulting in a bad 

 mixture, the preparation will have a greenish cast, and if this is very pronounced, 

 the mixture will inj ure the foliage. 



In order to make certain that the copper sulphate is properly neutralized by 

 the lime, the yellow prussiate of potash test may be used. A small bottle contain- 

 ing a 10 per cent solution of yellow prussiate of potash can be secured from a drug- 

 gist. After stirring the Bordeaux mixture, a drop of this solution is allowed to fall 

 on the surface of the preparation. If free copper is present, the drop will imme- 

 diately turn reddish-brown in colour. Lime should then be added until the brown 

 colour fails to appear. If the reaction is complete, the yellow prussiate of potash 

 solution will remain a clear yellow until it disappears in the mixture. 



ADDING INSECTICIDES. 



One advantage of Bordeaux mixture is the possibility of adding arsenical 

 insecticides to the preparation, and thus of spraying at the same time for diseases 

 and the codling moth and leaf -eating insects. Paris green, at the rate of one-quarter 

 pound to fifty gallons of Bordeaux mixture, may be considered as the standard for- 

 mula for this purpose. London purple, arsenate of lead, and other arsenicals may 

 be used in the same way. Bordeaux mixture may be considered as so much water in 

 the formulas for this class of insecticides. As a matter of fact, the slight excess of 

 lime in the standard mixture renders it an especially suitable medium for distributing 

 those insecticides. 



DUST BORDEAUX MIXTURE. 

 Formula.— The formula given by Mr. W. M. Scott, of this Bureau, for dust 

 Bordeaux mixture and the method of preparation are as follows : 



4 pounds of copper sulphate in 4 gallons of water. 

 4 pounds of lime in 4 gallons of water. 

 60 pounds of slaked lime dust. 



