Dark, dot-like spots appear on the leaves. Later the spots grow into each other and spread more or less over the whole leaf. The leaf margins roll up and wither. Infected leaves fall off at abnormal stages, and bushes are defoliated to a large extent in midsummer.
Anthracnose is caused by a fungus that hibernates on fallen leaves. In spring, spores grow on the old leaves and are carried by the wind to the young leaves, where they cause a new infection. In humid climates, the fungus forms new spores on the infected leaves. These help to spread the fungal spores and with them, the disease.
When you notice first spots, cut the affected leaves.
Always consider an integrated approach with preventive measures together with biological treatments if available. Fungicides of the strobilurins family, or those based on copper, fluazinam, pyraclostrobin or cyprodinil and fludioxonil can be applied.