Worldwide distribution. Temperate as well as tropical countries. A fungus causes the head rot; it attacks many vegetables and also causes seedling 'damping-off'. An important disease.
It survives in soil either living on dying and dead plants or as dormant balls of fungal growth (called 'sclerotia') which are splashed onto plants to germinate, infect, and rot the leaves, binding them together with cottony fungal growth.
Cultural control: Grow seedlings in either soil-less potting mix, or in pasteurised soil, and clean trays or pots; avoid wounds to plants during cultivation; allow crop remains to decompose completely before replanting; grow root crops in rotation with cabbages.