Spores germinate at wound sites, resulting in infection and eventual cankering. Spore-producing structures ultimately form in the new cankers, producing more spores for subsequent infections. The spore-producing structures generally form 4 to 6 weeks after a cankered branch dies. The fungus overwinters in diseased tissue of living hosts and in stem debris on the ground. If cankers are allowed to remain for several years, a second spore-producing structure, the perithecium, develops in the diseased tissue and produces ascospores.
Infection can occur anytime during the year, except during very hot and dry, or cold weather.
In Idaho, most infections occur during spring and early summer when temperatures are mild and moisture from rainfall is high. There is currently no cure for infected trees. Prevention and sanitation practices are the best management approaches. Use the following four steps concurrently. Winter injuries are the most common infection sites.