This vine disease (also known as dry rot) originated in North America and, after phylloxera and the two types of mildew, reached Europe as a "fourth import" in the early 1880s. It should not be confused with black spot disease. Black rot was identified in 1883 by the French viticulture expert Pierre Viala (1859-1936) in the laboratory of Montpellier. It occurs mainly in France, Italy, southern Switzerland and occasionally in German wine-growing regions and is spreading more and more. The disease is caused by the fungus Guignardia bidwelli (rust fungi). Prolonged rainfall in May and June with warm weather promotes the development and spread.