Powdery mildew produces ash-grey spores on leaves.
Flag shoots are the main source of infection. Phote courtesy of T. Wicks, Senior Plant Pathologist, South Australian Research and Development Institute. Red-brown to black blotches on mature canes are caused by powdery mildew infection early in the season. Mildew infection can cause delayed maturity, retarded growth and splitting of berries. A spray strategy for controlling powdery mildew.