370 



MANUAL OF FRUIT DISEASES 



Symptoms. 



In the beginning the disease is confined to a single branch or 

 twig ; but from year to year other branches are affected until the 

 whole tree is involved. Very frequently one or more twigs are 



killed before the 

 trouble extends to 

 the rest of the tree. 

 In many cases three 

 to six years elapse 

 before the tree is 

 wholly killed. 



The external 

 signs of the disease 

 are confined to the 

 leaves. Affected 

 foliage generally re- 

 mains normal as to 

 size and form, but 

 the surfaces, instead 

 of exhibiting the 

 normal green color, 

 show a peculiar 

 ashen gray luster; 

 the color more 

 nearly approaches 

 that of lead than 

 any other which 

 has been suggested 

 (Fig. 108). This 

 peculiarity is no- 

 ticeable at a great 

 distance from the 

 trees as well as 

 upon closer exami- 



FIG. 108. Silver-leaf : leaves on upper shoot 

 silvered ; leaves on lower shoot healthy. Twigs at 

 right showing fruiting bodies of the causal fungus. 



