56 FUNGOUS DISEASES AND SPRAYING 



spores before or immediately after they germinate without 

 injuring the host plant. Such a substance is called a/t/.n^icic?e. 

 The method of application is usually b}^ spraying. 



Fungicides. Only a few of the more useful fungicides will be 

 considered here. 



Copper sulphate ( common names, blue vitriol, blue stone ) 

 is the most generally used fungicidal substance ; it is used both 

 in a simple solution and as the basis of Bordeaux mixture. 



The simple solution is made by dissolving one pound in 

 twenty-five gallons of water. This is useful for disinfecting 

 trees and shrubs when not in foliage. 



The simple solution of blue vitriol when applied to leaves or 

 other green parts of plants will cause '' burning" ; the addition 

 of lime to the solution will prevent this injury. This combina- 

 tion is called Bordeaux mixture. 



The following is a good formula for the Bordeaux mixture : 



Blue vitriol ... 5 lbs. 

 Lime ( fresh ) . . . 5 lbs. 



Water .... 50 gallons. 



Dissolve the vitriol in water, hot water will do it more 

 rapidly ; slack the lime ; dilute each with as much water as can 

 be done conveniently, the more the better, then mix and stir 

 thoroughly. 



If much spraying is to be done, considerable time may be 

 saved by making a stock solution of blue vitriol. If this is 

 made of such strength that two quarts contain one pound it 

 can be measured readily ; the quantity required for a barrel of 

 the mixture will be two and one half gallons. The lime also 

 may be slacked beforehand provided it is kept covered with 

 water until used. In this condition, however, the lime is not . 

 so conveniently measured ; a good way is to use a test to de- 

 termine when suflScient lime has been used. If a little yellow 

 prussiate of potash is dissolved in water and a few drops 

 added to the Bordeaux mixture no change will be noted, beyond 

 perhaps a slight yellow color, if enough lime has been used ; 

 if, however, too little has been used, a brown color will appear 

 and more lime must be added ; a small excess of lime will do 

 no harm. An ounce of the yellow prussiate, which may be 



