Definition: black rot

A vine disease caused by a microscopic fungus that parasitises shoots, forming brown-black spots on the leaves and berries, which cause the grapes to wither. This disease appeared very late in Switzerland (1989). Prophylactic measures to reduce the potential for infection in vineyards are important, particularly the removal of abandoned vines. Chemical control remains essential, but is preventive. Susceptibility to black rot is highest from the pea stage until the bunches close. From this stage until veraison, susceptibility decreases. As soon as the berries contain 8% sugar, the risk of contamination is virtually zero.