Phylloxera is a pest of grapevines worldwide, originally native to the Mississippi valley in North America. These tiny, pale yellow sap-sucking insects, related to aphids, feed on the roots of grapevines. In grapevines, phylloxera can result in premature defoliation, reduced shoot growth, gradually cutting off the flow of nutrients and water to the vine, reduced yield and quality of the crop. Nymphs also form protective growths on the undersides of grapevine leaves and overwinter under the bark or on the vine roots.
In the late 19th century the phylloxera epidemic destroyed most of the vineyards in Europe, most notably in France. Phylloxera was inadvertently introduced to Europe in the 1860's, on imported North American vine-stocks / plants.
Because Phylloxera is native to North America, the native grape species there are partially resistant. By contrast, the European wine grape is very susceptible. The epidemic devastated most of the European wine growing industry. In 1863, the first vines began to deteriorate in the southern Rhone region of France, then the problem spread rapidly across the continent. In France alone, total wine production fell from 84.5 million hectolitres in 1875 to 23.4 million h/l. Some estimates hold that between 70-90% of all European vineyards were destroyed, almost 2.5 million ha / 6.2 million acres.
In France, some grape growers were so desperate that they buried a live toad under each vine. Areas with sandy soils were spared, and the spread was slowed in dry climates, but gradually it spread across the continent. A huge amount of research was devoted to finding a solution to the Phylloxera problem, and two major solutions gradually emerged: hybridization and resistant rootstocks that have been used the world over.
The only European grape that is natively resistant to Phylloxera is the Assyrtiko grape which grows on the volcanic island of Santorini, Greece, although it is not clear if the resistance is due to the rootstock itself or the volcanic ash on which it grows.