Internodal shortening is often pronounced. As the mildew colonies age they eventually turn gray or brown. 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.