GRAPE DISEASES 239 
only a slight change in color; within this area are found numer- 
ous brown punctations, which do not unite to form a dead, 
brown spot in the leaf-tissue. The disease on the lower surface 
of the leaf is at first similar to that on the upper, but is very 
soon covered by a downy, white growth (Fig. 61) which is 
most pronounced just beneath the 
greenish yellow portion mentioned 
above. On the brown portion the 
whitish felt, the mildew-pathogene, 
soon disappears. The amount of 
mildew on a leaf depends on weather 
conditions and on the variety. The 
lower portion of a vine may be de- 
nuded of its foliage. 
The canes, leaf-petioles and ten- 
drils are subject to attack, especially 
in wild varieties. At first the af- 
fected portion has a water-soaked, 
shiny appearance, which is attended 
by a local swelling of the tissue. 
The lesion is bare at first, but soon 
the mildew covers it. In older 
cases the affected area becomes 
brown and dead, and a depression 
results. In cases of severe attack 
the cane is dwarfed, the leaves 
remain small, and the cane may Fi. 62. — Downy-mildew on 
_ : grape-shoot. 
die (Fig. 62). : 
The fruit (Fig. 63) and flowers of wild varieties commonly 
show the downy-mildew. The attack may come at any time 
from flowering to maturation. The first sign of the trouble 
on the fruit is a hardening of the berry, together with a change 
from its normal color to a grayish blue lead-color. It is during 
this stage that the mildew appears. In later stages the berry 
