Black Rot

fungal disease which is one of the most economically important diseases of vines in the north-eastern United States, Canada, and parts of Europe and South America. The disease is native to North America and was probably introduced to other countries by contaminated cuttings. It was introduced to France, for example, on phylloxera-tolerant rootstocks as early as 1885. The disease is caused by the fungus Guignardia bidwelli, which attacks young shoots, leaves, stems, and berries. The disease spreads only in mild, wet weather. Crop losses can be high, up to 80%. Control of the disease is based on fungicides sprayed from spring up to fruit ripening and removing from the vineyard infected mummified berries. The disease is causing renewed concern because of its recent spread in Europe. As might be expected from the origin of the disease, some native American species are tolerant.