Galls develop on infected junipers, and when mature produce reddish-brown, pointless, gelatinous horns during rainy spring weather. They release spores that are infectious to the other hosts. These spores are dispersed through wind at night and early morning to fruit or leaves of the broadleaf host (hawthorn). Infections will occur if moisture is available for 4-6 hours, and temperatures are adequate. When the spots appear on the surface of leaves, light colored bristles appear on the underside of these leaf spots. In late summer, these structures will release spores that will infect the juniper host, completing the life cycle.
Even though the bright red and orange leaf spots and the gelatinous galls calls attention to the leaves, the disease rarely causes serious damage to its hosts.
You can manage this with fungicide applications beginning when flowers are opening, use of resistant cultivars and avoiding planting the two hosts close together.