206 MANUAL OF AMERICAN GRAPE-GROWING 



first insect after hatching making its way to the leaves where 

 it becomes a gall-maker and gives rise to a new generation of 

 egg-laying root-feeders. On varieties and in regions where 

 the gall form is not found, the insect probably goes directly 

 from the winter egg to the roots. Once the pest is established 

 on the roots, generation follows generation throughout the 

 growing period of the vines, as many as seven or eight occurring 

 in one season. 



From midsummer until the close of the growing season, some 

 of the eggs deposited by the root-feeders develop into nymphs 

 which acquire wings and emerge from the soil to form new 

 colonies from eggs deposited on the under side of the leaf. 

 An individual insect deposits from three to six eggs of two sizes, 

 from the larger of which come the females and these, after 

 fertilization, move to the rough bark of the vine and deposit 

 the winter egg for the renewal of the cycle. 



Several methods of control ha\'e been employed in Europe 

 and California, as treatment by carbon bisulfide injected in 

 the soil ; flooding in vineyards that can be irrigated ; confining 

 the vines to sandy soils; and, most important, planting vines 

 grafted on resistant stocks, there being great variation in im- 

 munity of species of American grapes to phylloxera. The 

 subject of stocks resistant to this pest has been discussed in 

 Chapter IV and need not be taken up again. East of the 

 Rockies, treatment is not necessary with American grapes. 



TJtc grape root-worm. 



The grape root-worm is the most harmful of the insect 

 pests of grapes in the grape-belt along the shores of Lake 

 Erie in Ohio, Pennsylvania and New York. This root-worm 

 (Fig. 37) is the larva of a grayish-brown beetle (Fidia 

 viticida), shown in Fig. 38. The worms feed at first on 

 the rootlets and later on the bark of the larger roots 

 of the vines so that the hijured ])lants show roots de- 



