Plants affected by basal rot show progressive yellowing and dieback from tips of leaves. Affected roots are dark brown to dark pink. A white fungal growth is sometimes evident at the base of infected bulbs. When an infected bulb is cut vertically, a brown discoloration at the base of the plant is apparent. Later this tissue becomes pitted and shows a dry rot. Under dry conditions, the base of the plant and dry outer scales crack open.
Solutions
The basal rot fungus survives indefinitely in soil. Avoid garden sites with a history of basal rot problems and rotate 3 to 4 years out of onions and garlic. Control soil insects and foliage diseases, as infection occurs through wounds or in the vicinity of old root scars at the base of the bulb. Plant in cool weather; the disease is favored by soil temperatures in the range of 57 to 90°F. Direct seed onions; basal rot is more prevalent in transplanted onions. Store at low temperatures because infection is favored by warm conditions.
