Note 5 — Chapter I · THE OLD WORLD GRAPE

The phylloxera (Phylloxera vastatrix Planch.) has four forms: the leaf-gall form, the root form, the winged form, and the sexual form. Individual leaf insects produce from 500 to 600 eggs, the root insect about 100, the winged insect from 3 to 8, and the sexual insect but 1. The last is laid in the fall on old wood; the following spring a louse hatches from it and at once goes to the upper surface of a leaf and inserts its beak. The irritation thus produced causes a gall to form on the lower side of the leaf. In fifteen days the louse becomes a full-grown wingless female and proceeds to fill the gall with eggs after which it dies. In about a week females hatch from the eggs and migrate to form new colonies. Several generations of females occur in a summer. At the approach of winter the lice go into the ground where they remain dormant until spring when they attack the roots forming galls analogous to those on the leaves and passing through a series of generations similar to those above ground. In the fall of the second year some of the root forms give rise to winged females which fly to neighboring vines. These lay eggs in groups of two or four on the wood of the grape. The eggs are of two sizes; from the smaller size, males hatch in nine or ten days; from the larger, females. In the sexual stage no food is taken and the insects quickly pair. The female produces an egg which fills its entire body and after three or four days lays it, this being the winter egg, the beginning of the cycle.

There are no remedies worthy the name and the only efficient preventive is to graft susceptible varieties on resistant stocks. Species are resistant about in the order named: V. rotundifolia, V. riparia, V. rupestris, V. cordifolia, V. berlandieri, V. cinerea, V. aestivalis, V. candicans, V. labrusca, V. vinifera.