White rot is a plant disease, caused by the fungal pathogen Sclerotium cepivorum in onions, leeks and garlic. Sclerotium cepivorum forms small black bodies which are the sclerotia or survival structures of the fungus.

The fungal sclerotia can remain dormant in the soil for as long as 20 years. White rot only affects allium crops particularly onion, leek and garlic crops, infection can occur at any stage of crop development if conditions are conducive. The pathogen spreads through physical movement in the soil and can cause root rot, white fluffy fungal growth at the base of the bulb, wilting of leaves, and yellowing and dieback of leaf tips.