Grape Powdery Mildew
Grape Powdery Mildew (Uncinula necator) can often result in reduced vine growth, yield, fruit quality and winter hardiness. The quality of wine can be affected when only 3% of the berries are infected.
The fungus first appears as tiny red flecks on the upper surface of the leaves. These symptoms lead to white/ grey patches of fungal growth on the leaves berry surface and ranchises. On young shoots and leaves infection if likely to be more sparce, however the most obvious symptom is a grey or purplish discolouration when viewed from a distance.
If blossom clusters are affected fruit set will be reduced and because Powdery Mildew attacks all green material, the cluster stems are often attacked resulting in berry drop. Later in the season infected berries are often covered in white, powdery growth or misshapen with brown spots on the surface.