Downy mildew (vine) / vine peronospora [Plasmopara viticola]
The more humid the months of April and May are, the earlier a Peronospora primary infection might occur. The over-wintering spores only germinate under humid weather conditions and at a 24 hours average temperature of at least 8 °C.
Pattern of damage
Round, yellowish bright, oily shining spots on the upper side of the leaves (Picture 1). A dense, white fungal lawn develops on the underside. Infected grapes turn reddish-brown and the surface leathery (Picture 2).