246 FARM FRIENDS AND FARM FOES 



vents them from growing to as large a size as they would 

 if not affected. The extent of this dwarfing is illustrated 

 in the figure below. The disease may be prevented by 

 spraying with fungicides, the self-boiled lime-sulphur wash 

 being one of the best for this purpose. 



DWARFED BY 

 APPLE SCAB 



A closely related fungus causes the Pear Scab, which is 

 often destructive to certain varieties of pears. Its life his- 

 tory and control are practically the same as the Apple 

 Scab. 



BITTER ROT OF APPLE 



This disease causes losses of millions of dollars in the 

 United States almost every year. It is generally noticed 

 upon the fruit, especially as it approaches full size. Small 

 brownish spots may be seen at first ; these gradually en- 

 large and commonly spread over much of the apple, caus- 

 ing it to fall. Many of the smaller fruits, however, re- 

 main upon the tree, shriveling to a mummified condi- 

 tion, in which they may hang to the twigs until the next 

 spring. 



After the mycelium of the fungus has been growing in 

 the fruit tissues for a time, it develops upon the surface 

 characteristic blackish pustules in which great numbers of 



