THE GRAPEVINE ROOT-BORER 



249 



The grapevine phylloxera attacks both the leaves and the roots 

 of the grapes. It is seldom serious except in California and in 

 foreign grape growing regions. This is true at least of the root 

 forms. Leaf-galls are often found on American grapes in other 

 sections. When the roots are seriously attacked, they are appa- 

 rently poisoned by the insect and decay follows. The vines are 



Fig. 177- 



-Downy mildew disease causes green fruit to become hard and dry; the riper 

 fruits shrivel and turn brownish in color. (Minnesota Station.) 



frequently killed. Resistant varieties must be used for stocks in 

 order to control the root form of this pest. If European grapes are 

 grafted upon American stocks, they are usually not seriously 

 affected by this enemy. 



The grapevine root-borer feeds on the roots of the grape some 

 distance under the ground. Its work is not usually noticed until 



