Downy mildew (DM) of grapes caused by the pathogen Plasmopara viticola is a highly destructive disease of grapevines that occurs in most parts of the world is favoured by warm, wet conditions during the vegetative growth of the vine. Downy mildew affects the leaves, shoots, berries and fruits of grapevines. Severe yield losses even up to 100 % can occurs in one season