THE DISEASES OF PLANTS 



III 



This scab is caused by a fungous growth upon the surface 

 of the potato. It of course lessens the selling price of the 

 potatoes. If seed potatoes be treated to a bath of for- 

 malin just before they are planted, the formalin will kill 

 the adhering fungi and greatly diminish the amount of 

 scab at the next harvest. 



Before planting, seed potatoes should be soaked in a weak 

 solution of formalin for about two hours. One half pint of 

 formalin to fifteen gallons of water makes a proper solution. 



FIG. 98. YIELD FROM Two FIELDS OF SAME SIZE 

 The one at top was sprayed ; the one at bottom was unsprayed 



One pint of formalin, or enough for thirty gallons of water, 

 will cost but seventy-five cents. Since this solution can be 

 used repeatedly, it will do for many bushels of seed potatoes. 



Late Potato Blight. The blight is another serious dis- 

 ease of the potato. This is quite a different disease from 

 the scab and so requires different treatment. The blight 



