Downy Mildew / Míldio

This disease, which mainly affects the leaves and bunches of grapes, only began to cause significant damage to Madeiran vineyards in 1912. The white powdery spots that characterize it are due to a fungus of the Peronosporaceae family – Plasmopara viticola – whose branches emerge through the stomata of the leaf and form conidia at the ends of their last ramifications. The mycelium of the fungus lives inside the green organs of the vine and directly harms the plant. The spread of downy mildew occurs not only through spores (conidia), but also through eggs or oospores resulting from the fusion of two dissimilar cells. Bordeaux mixture has been effective in the preventive treatment of downy mildew.