Minute brown fruit bodies known as cleistothecia can form on the aging colonies. Infection of a Granny Smith pedicel. Infection results in a the production of a net-like pattern on the fruit surface. Fruit is most susceptible during the period around petal fall. The fungus overwinters as mycelium in dormant infected buds.
Leaves are susceptible for only a few days after emergence.
Early-season secondary infections are limited mostly by low temperatures. The amount of overwintering inoculum is proportional to the severity of the winter, i.e. less inoculum survives a severe winter. Healthy buds can survive temperatures 2-10 C lower than infected buds. Conidia are very sensitive to temperature. The inoculum for pear fruit comes from infested apple orchards.