Insect and Fungous Enemies ofthe Grape. ~§ 58 
ground when disturbed. This stage of the disease is sometimes called 
“brown-rot.” 
Besides the summer spores mentioned, there is also produced within 
the diseased tissues of the leaves another form of reproductive 
body, sometimes called a winter or resting spore. ‘These spores are 
produced in much smaller numbers than the summer spores and are 
provided with a rather thick, dark-colored outer covering apparently 
intended for their protection during the winter. 
Fie. 58.—The fungus causing downy mildew. 
a, Fertile filaments of the downy mildew fun- 
gus, Showing the manner in which the summer’ Fie. 59.—A bunch of young grapes 
spores are borne; b, two Summer spores; ¢, 9 partially destroyed by ‘ gray-rot.” 
winter, or resting spore. (All highly magni- This is a form of the downy mil- 
fied.) dew affecting the very young fruit. 
This disease, like the black-rot and many others, develops most 
rapidly and does most injury during hot, wet weather and does not 
cause trouble in arid regions. 
TREATMENT. 
It is desirable to destroy as many as possible of the old diseased 
leaves, shoots, and berries, which may contain the winter spores. 
Thorough spraying on the under sides of the leaves, as recommended 
for the black-rot, will effectively control this disease. 
