178 



PRINCIPLES OF PLANT CULTURE 



in 40 gallons of water. Corrosive sublimate solution 

 (1 pint in 1000 of water) is used in a similar way, e.g., 

 with potatoes. 



Fig. 80. — Apple-scab on leaves. 



328. Spraying aerial parts with fungicides aims so to 

 coat the surfaces of the healthy leaves, fruit or branches, 

 that spores falling upon them will be destroyed. Its 

 purpose is always to prevent disease rather than to cure 

 it. The spraying must, therefore, precede the spread of 



