APPLE DISEASES 



65 



Symptoms. 



The presence of apple-rust in any locality may be detected 

 by examining the apple or the cedar. On the apple leaves 

 young spots may be found from April to June. At first these 

 are seen on the upper surface as minute pale-yellow areas 



FIG. 17. 



Apple-rust; on lower surface (on leaf at extreme left), and on 

 upper surface (three leaves on right). 



(Fig. 17, right). These enlarge, become darker, and finally 

 are orange-colored. On the upper surface of the spots the 

 fruiting bodies of the pathogene develop, first as minute, yellow, 

 flask-shaped pustules, which finally turn black (Fig. 17). The 

 leaf tissues beneath the spots become swollen and on the lower 

 surface another kind of fruiting body is produced (Fig. 17, 

 left). This one is cup-shaped and considerably larger than the 



