Insect and Disease Control 269 



rapid drying of dews and rains is doubtless advantageous. 

 Moreover, the mildews that occur on other hosts usually 

 yield quickly to sulfur sprays. Peach trees which are well 

 sprayed for the more serious diseases will rarely require 

 separate treatment to control the mildew. Should it become 

 threatening at any time, it is probable that the self-boiled 

 lime-sulfur mixture or flowers of sulfur in water w^ould be 

 effective. 



Frosty-mildeio {Cercosporella persicoe) 



This disease apparently occurs more frequently from the 

 central Atlantic states southward than in other peach regions. 

 However, it is not of special concern even in those regions 

 where it is most prevalent. 



The conditions described as favorable for powdery-mildew 

 are likewise favorable for this disease. 



Course of development. 



An area of infection appears on the upper surface of a 

 leaf as a pale yellowish spot, while the corresponding area 

 on the other side develops a delicate, frost-like growi;h 

 which consists of the fruiting bodies. 



Methods of control. 



Though little experimental work looking to the control of 

 this mildew has been done, as there is rarely any necessity 

 for specific action to that end, it is probable that the treat- 

 ment suggested for powdery-mildew would prove effective. 



Rust (Puccinia spinosoe) 



This disease is very widespread and has as its hosts prac- 

 tically all stone-fruits, besides some wild herbaceous plants. 



