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Phylloxera, a North American insect that kills the vine by feeding on the root, was not identified until the late 19th cent. It caused the failure of early plantings of European grapes in the E United States and, beginning about 1860, spread around the world, probably traveling on resistant American vines, infecting V. vinifera from France to Australia to California. French and American researchers finally saved the world's wine industry by grafting phylloxera-susceptible European vines onto resistant E American roots. Virtually all wine grapevines in Europe and California are grafted to rootstocks of E American origin. In 1979 phylloxera B overcame the resistance of the dominant rootstock in Northern California vineyards; thousands of acres subsequently were replanted with more resistant rootstocks.
Besides phylloxera, the V. vinifera of the Pacific slope is harassed by a variety of pests and diseases, including black measles, little-leaf, nematodes, red spiders, rabbits, and gophers. Among the afflictions of vineyards in the E United States are mildew, a devastating fungal disease; the grape-berry moth, which destroys fruit by causing it to color prematurely; the grapevine beetle, which eats the new buds in spring; climbing cutworms, which hide in the ground during the day and feed on the buds at night; black rot, which shrivels the fruit; and crown rot, which destroys the vines of some varieties.
Prophylaxis of healthy vines and treatment of afflicted ones are but two of the intensive, continuous aspects of viticulture. From the early stages of tending a vineyard, when appropriate vines must be selected and congenial soil chosen for them, through the operations of cutting, layering, grafting, planting, and fertilizing, up to the gathering of the crop, the grower must apply equal measures of skill, knowledge, and industry.
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