Pink spores appear in wet weather on the undersides of the leaves. It overwinters on fallen leaves and produces spores in the spring which infects leaves and twigs through clipping wounds and cracks. Other spots can also appear, developing into large necrotic areas with black streaks down the stem. Patches of grey fungus also appears on the lower leaf surface. Leaves will fall prematurely due to blight.
This disease is caused by two different fungi which may be present on the plant at the same time.
The best method of controlling this disease is to make sure that all tools are cleaned after use, fallen leaves are raked up, infected branches should be pruned out immediately and new plants planted in the garden should be disease free.