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 
Fic. 108. — Silver-leaf: leaves on upper shoot 
silvered ; leaves on lower shoot healthy. Twigs at 
right showing fruiting bodies of the causal fungus. 
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 
thesurfaces, 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- 
