Brown rot attacks apples and pears on trees and in storage, spreading easily by contact. Brown patches develop rings of pale spots, or fruit can turn entirely black.
Grey mould affects fruit, carrots and squashes, especially in overcrowded, badly ventilated stores. The fungus forms a fluffy grey mould, releasing clouds of spores.
Bacterial soft rot is common on root crops and onions. Soil-dwelling bacteria enter via wounds, initially causing foul-smelling lesions, and can rot the insides entirely, leaving only skin.
Onion neck rot is a fungus that develops after 10 weeks of storage. Outer scales soften and the neck browns. It does not spread in storage but may have infected many bulbs going into storage.
Potato dry rot causes dark brown lesions and discolored, mouldy flesh. Spores of this fungus are carried on adhering soil and enter wounded tubers in too-warm storage.
Article from The Garden Journal, RHS, Dec 2010