The incidence of brown rot and blossom blight is related to temperature and duration of wetness.
As little as 3–5 hours of wetting at 20C may lead to significant infection.
Within 24 hours of wetting, severe blossom infection may occur regardless of temperature.
Optimum conditions for blossom infection of peach and cherry is 20–25C with showery conditions and cool nights.
Temperatures above or below the optimum range may delay infection but not prevent it. Frequent rain periods and warm conditions at or near harvest lead to fruit infection within 48 hours.
Control of the disease without the use of fungicides is usually not possible.
However, measures can be taken to reduce the amount of the disease in the current and subsequent seasons.
In particular, it is important to collect and destroy any diseased fruit or flowers whether they are still attached to the tree or have fallen.
Mummies are diseased fruit that have dried. The spores on mummies provide inoculum for infection in the subsequent season. Consistent collection and destruction of mummies reduces the amount of disease present in orchards.
Control insect pests that spread the disease. Brown rot spores need a wet surface to germinate and infect tissue, and injury can provide a surface wet with sap or fruit juice.
Control insect pests that cause fruit injury such as oriental fruit moth, light brown apple moth and dried fruit beetles.
Good insect pest control is essential for successful brown rot control.
See this article in Tree Fruit Oct 2019