Pocket plum disease

 This summer there have been some spectacular local outbreaks of pocket plum disease, affecting sloes on blackthorn on the Durham coast near Hawthorn dene  and bird cherry fruits in Weardale. It's caused by the fungus Taphrina pruni, which induces the fruits to swell, become spongy and fill with watery fluid. In bird cherry (bottom picture) the normally spherical, shiny black fruits become banana-shaped. No seeds are formed inside these deformed fruits, instead there is an empty 'pocket'.