336 



BULLETIN 226. 



young apple or on the leaf and there grows, sending its roots 

 (mycelium) into the tissues of the apple. At first the infected spot 



is invisible, later 

 it causes the skin 

 to take on a deep 

 olive-green color, 

 dom noticed until 

 season when it 

 the skin and 

 scab. Fig. 79 

 apple that has 

 this stage. The 

 the apple is 



the FlG ' 79- The outer skin (cuticle] ruptured. 



exposing the funsus 



\ 



but it is sel- 

 still later in the 

 breaks through 

 causes the black 

 shows an 

 just reached 

 outer skin of 

 breaking away 

 black fungus, 

 "gone to 



exposing 



1-1 i 

 which has now 



seed." In time the spores are blown and washed away and some of the 

 fungus cells and dead tissue are more or less worn away so that the color 



may become a reddish-brown, 

 due to the exposed dead corky 

 tissue. The scab spots on the 

 left in Fig. 80 show the spores 

 and fungus cells beginning to 

 leave from the center of the 

 spot. The large scab on the 

 right shows the rusty scar that 

 is left after the disease tissue 

 has scaled off. Farmers describe 

 this change by saying that " the 

 fungus leaves the apple," or 

 " the fungus changes to rust." 

 If this takes place before the 



FIG. 80. The diseased tissue scaling off from 

 the apple. 



apple is picked, the appearance 



