Infection by the fungus can take place anytime between mid-July and mid-September. Spores of the fungus are expelled during wet weather and must land and germinate in a wounded portion of a twig or branch. Germinating spores cannot penetrate directly through intact bark, and infection through needles is not known to occur. In the summer following that of infection, infected branches are girdled by the fungus and die. Browning of needles associated with branch death may occur rapidly with the onset of hot, dry weather in early summer.
Fruiting occurs 2-4 weeks after branch death and is evident by the appearance of clusters of small (1/16 inches diameter), cup-like structures in bark crevices and other openings. When dry, the structures are light brown and shriveled, but upon wetting they open to expose an orange inner surface characteristic of the fungus. Spores produced in these fruiting bodies are wind-disseminated to new sites of infection.
At present, there are no chemicals registered or recommended for control of Cenangium canker. Dead branches should be pruned and buried or composted. The combination of environmental factors necessary for severe disease incidence usually does not occur each year.
10/77 Prepared by: George W. Hudler, Associate Professor/Plant Pathology, Cornell University