🦠 Plasmopara viticola

Plasmopara viticola is the organism that causes downy mildew of grapevines. It looks like a fungus but in fact belongs to a different group. It comes from America. It reached Europe in the second half of the 19th century, around the same time as phylloxera, and did great damage.

The organism attacks leaves, shoots and bunches. Yellow oily spots appear on the leaves and a white bloom underneath. Infected berries shrivel and dry. The disease likes warm, damp weather, so it is especially dangerous in rainy years. The crop can be almost completely lost.

Mildew is fought by prevention: airy rows, proper pruning and sprays. The first remedy was Bordeaux mixture, a solution of copper sulphate and lime devised in France. Today resistant varieties are also bred. Plasmopara viticola counts as a vine disease and is tied to downy mildew. It has to be watched throughout the whole season.