Powdery mildew 

Powdery Mildew is a common fungus that affects a wide variety of plants. The first very small lesions (orange to black in colour) are frequently found on the underside of leaves. Then they become more apparent on the upper side of leaves as well. These lesions will increase in size and number if left unchecked. severeley infected leaves will become brittle and drop off. Their appearance then changes to the grey or whitish powder comonly seen, which can then infect berries. berries infected late in the season are then prone to splitting, making them susceptible to Botrytis.