Blue to violet spots appear on the shoots and the bark bursts open. Subsequently, the spore cushions form blisters on the shoots. The plant drops its leaves early in the year. In spring the affected shoots do not sprout.
The pathogen enters the plant with humid spring weather and hibernates in the affected shoots.
Remove infected shoots. After an infection, use a plant fortifier, so the plants are able to fight the fungi. You can choose more resilient varieties, such as Glen Moy, Glen Rosa, Julia, Malling Admiral or Leo.
Fungicides based on Lime Sulfur or Captan/Fenhexamid mixtures can be used.