A white fungal growth is sometimes evident at the base of infected bulbs. Later, the stem plate tissue becomes pitted and shows a dry rot. Under dry conditions, the stem plate and dry outer scales crack open. Basal rot can continue in storage. The fungus survives indefinitely in soil.
Infection occurs through wounds or in the vicinity of old root scars at the base of the bulb.
Basal rot is more prevalent in transplanted onions than in direct seeded onions. Avoid fields with a history of basal rot problems and rotate 3 to 4 years out of onions, garlic, and leeks. Control soil insects and foliage diseases. Cure onions properly before storage. Store at cool temperatures since infection is favored by warm conditions.