o 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 have 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 immunity 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.

_The 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 injured plants show roots devoid of rootlets and bark
channeled by the pest. So plain is the work of the root-worm that the
grower never need be at a loss as to the cause of vines injured by
this pest. The worms feed during the latter part of the growing
season, reaching full growth at this time. The next June they
transform into pupae and in late June or early July emerge as adult
beetles.

[Illustration: FIG. 37. The grape root-worm.]

[Illustration: FIG. 38. Root-worm beetle.]

The presence of the adult beetles is more easily detected on the
foliage than is that of the larvae on the roots, for the feeding
beetles ravenously devour the upper sides of the leaves, leaving
chain-like markings, shown in Fig. 39, their destructiveness
decreasing somewhat after a few days from their first appearance. A
fortnight after the beetles begin their attack on the foliage the