On Crops: Parsley
Cool temperate climates where parsley is winter hardy
Plants grow normally until a late summer or early fall, when individual plants wilt and then collapse following a period of heavy rain. If you pull the plant it will break off at the crown, and the crown will have a tan, corky appearance. Individual plants may fail, while others nearby continue to look healthy. Established plants being grown though winter may die at any time from root rot.
The fungi invade the plant's roots and crown, causing the plant to clog up and fail. Infected plants are inedible.
Rotate where you grow parsley, and consider using raised beds to enhance drainage. These fungi need very wet soil conditions to grow, so keeping parsley covered with a plastic tunnel through winter often prevents problems.
Pull up affected plants and compost them. Place a pile of compost on the spots where the diseased plants grew.