Most spores are released from bud swell to petal fall. None are released after September 1. The disease is most severe after winters in which mild spells are interspersed with cold periods. Periods of hot, dry weather during the growing season probably also predispose the plants to infection. The fungus overwinters in infected plant parts.
Symptoms first appear on smaller twigs.
The disease then spreads into larger branches and may affect the crown. It is possible for Phomopsis to spread downward in injured canes to the crown and then progress upward on new canes. This is rare and usually only occurs where the crown itself has been injured, after a particularly severe winter, or in highly susceptible cultivars. Young tissue initially shows no symptoms, then exhibit rapid wilting and dieback. Lesions, somewhat similar to those caused by Fusicoccum , but generally lacking the bulls-eye pattern, may appear on the stems.