The fungus overwinters in mummies formed the previous season, in blighted twigs and in cankers. An additional source of conidia are produced on apothecia. Apothecia are fruiting structures of the fungus which form on mummies that have fallen on the orchard floor. The first fungus spores are formed about the time the blossoms begin to open. Upon wetting, the spores are forcibly ejected into the air to be blown by the wind to blossoms.
Infected blossoms serve as a source of the fungus for future fruit infections.
Environmental conditions are important for the development of the disease. Warm, wet, or humid weather is very favorable for disease development. The severity of brown rot increases as the fruit ripens. Wounded fruit are more susceptible to infection. Mature fruit can completely decay in two days from the time of infection under favorable weather conditions.