Gummosis is usually associated with the cankers. The canker fungi overwinter in active cankers in living wood or in dead wood. Infection occurs where the bark is damaged or injured. Infection following cold injury frequently occurs in the crotch angles of affected trees. Other ports of entry for these fungi include pruning wounds, mechanical damage, insect damage and leaf scars.
Moisture is required for spore production, spore dissemination, and infection.
The rate of canker development following infection depends on temperature and the species of fungus involved. When temperatures do not favor fungal activity, calluses form. Canker activity resumes when temperatures again favor the fungus. This back and forth battle between the tree and the fungus usually ends with the fungus winning. Once the disease becomes established, it becomes increasingly difficult to control.