As the fruit matures, it becomes more resistant to the fungus. The fungus overwinters as mycelium in infected shoots and dormant peach buds. Flower buds of infected shoots often do not survive the winter. These conidia are disseminated by air currents and rain, causing new infections on expanding leaves, shoots, and young fruit. Young leaves and immature fruit are more susceptible to mildew.
Fruit become resistant with pit hardening and the leaves become resistant with age.
The disease is favored by dry, warm weather with moisture in the form of fog, dew, or high humidity. Free moisture is not required for spore germination. Germination can occur at relative humidities of 43 to 100 percent. When environmental conditions are favorable, new lesions will develop within ten days. A total of one to ten infections and greater than ten infections represents moderate and high risk, respectively.