Just like at other winemakers, our vines risk getting attacked by two types of this horrible fungal disease. It comes in the varieties of powdery and downy mildew.
Powdery mildew, also known as Oidium, can infect all green parts of the grapevine. Infection usually appears first on the underside of basal leaves as a white powder. Later on, the fungus can cause mottling, curling and withering of the leaves. Eventually, leaves dry out and drop off. Symptoms of infection on green shoots appear as dark brown to black lesions. On the canes, an old infection appears as reddish, brown areas. During the shoot period, petioles and other cluster parts can get infected, and berries are more likely to get infected 3-4 weeks after the bloom. An infection on the berries can appear as white and powdery, or dark and dusty. Powdery mildew can result in shrivelling or cracking of the berries, which then dry up or never get ripen.
Downy Mildew also attacks all green parts of the grapevine and is characterised by the presence of oil spots on the surface of leaves and white down that can be seen on the underside of the leaves, canes and bunches in periods of high humidity. It can cause significant impact on yield if control measures are not implemented. It can also cause leaves to drop off and berries to shrivel and crack if not treated in a timely matter.
Prevention is key. So we treat our vines with organic certified copper and sulphur based spraying solutions just after winter pruning, before flowering. Depending on the weather we do it several times during the vegetative season.