180 



PRINCIPLES OF PLANT CULTURE 



330. Bordeaux mixture is made of copper sulfate 

 (blue vitriol) and lime. There may be a considerable 

 variation in strength or proportions of the ingredients, 

 according to plant or conditions. A formula in common 

 use is the " 5-5-50," i.e., 5 pounds of copper sulfate, 5 

 pounds of lime and 50 gallons of water ; although weaker 

 mixtures, 4-4-50, or even 3-3-50 are gaining in favor. 



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Fig. 82. — Diagrammatic section through an infection by the apple- 

 scab fungus. 



To prepare the mixture, dissolve the copper sulfate in 

 one vessel, dilute with about one-half the total amount 

 of water to be used (25 gallons). Slake the lime in another 

 vessel, dilute with the balance of the water (25 gallons) ; 

 then strain the two together and stir thoroughly. The 

 light blue compound formed is the essential thing in the 

 fungicide. If allowed to stand, it gradually settles and 

 loses some of its fungicidal value, hence it is necessary 

 to have an agitator attached to the spray pump (304) 

 and the mixture should be freshly made as used. Since 

 the copper corrodes iron and other common metals, the 

 mixture is best made in wooden vessels and the pump 

 should have brass working parts. 



