Brown rot is a fungal disease of fruit that causes them to turn brown, shrivel and rot. It can happen while the fruit is developing on the tree from mid-summer onwards, or when the picked fruit is in storage. Affected areas are inedible, making the whole fruit inedible once the disease coverage is more-or-less complete.
Sometimes, as the affected fruit rots, buff-coloured pustules, often in concentric rings, appear on the surface of the fruit.
Affected fruit don’t always fall from the tree in autumn and remain on the tree throughout winter as shrivelled, “mummified” fruit. Where these touch the bark they create cankerous infections.
Sometimes in spring, during flowering, the flowers and the leaves on the fruiting spurs turn brown and shrivel up. This problem is known as blossom wilt and is caused by the same fungi. This forms a further source of the fungus to attack the fruit later in the year.