Phylloxera, common name for insects which include the grape phylloxera of American origin, which, accidentally introduced into France about 1859 on native American grape vines, spread through the principal wine districts of southern Europe and then throughout the world, causing enormous damage. In the United States the scourge was generally confined to European vines grown from their own roots. After these were uprooted, the problem abated. American vines were thought to be immune because of greater natural vigor and the thicker bark covering of their roots. But in the early 1990s grape phylloxera returned to the Napa and Sonoma valleys of California, and winegrowers were forced once again to replace damaged vines with more resistant stock.
The grape phylloxera occurs in four forms: the leafgall form (gallicola), the root form (radicicola), the winged or colonizing form, and the sexual form. The sexual insect lays the winter egg on the old wood. The young aphid hatching in the spring proceeds to a young leaf and deposits itself upon the upper surfaces. A gall that projects from the lower side of the leaf is gradually formed. The aphid reaches full growth in 15 days and gives birth to living young that migrate to all parts of the vine to form new galls.
Six or seven generations of these wingless females follow one another through the summer, frequently covering the leaves with galls. At the approach of cold weather the young proceed to the roots, remaining dormant until spring. In the spring the root is attacked by a series of generations of wingless females, which produce swellings on the rootlets. In late summer and autumn some of the root lice give birth to winged females, which escape through the soil and fly to neighboring vines, laying their eggs on the bark. Thus, the life cycle continues.
Scientific classification: Phylloxera make up the family Phylloxeridae of the order Homoptera. The grape phylloxera is classified as Viteus vitifolii.