Fusarium basal rot

Fusarium basal rot (Fusarium oxysporum f.sp. cepae) is a plant pathogenic fungus. Losses to this disease can occur in the field and later when onions are in storage. Like pink root, Fusarium basal rot can build up in soils where onions are grown year after year.

Symptoms
Symptoms may be observed in the field as yellowing leaf tips that later become necrotic. This yellowing and/or necrosis may progress towards the base of infected plants. Sometimes leaves of infected plants may exhibit curling or curving. Infected bulbs, when cut vertically, will show a brown discoloration in the basal plate. This discoloration will move up into the bulb from the base. In advanced infections, pitting and decay of the basal plate, rotten sloughed-off roots, and white, fluffy mycelium are all characteristic symptoms and signs of Fusarium basal rot. Sometimes, infected bulbs may not show symptoms in the field but will rot in storage.

Prevention
Like pink root, growers use a long rotation (4 or more years) to non-related crops as the key management strategy for reducing losses to Fusarium basal rot. Growers set healthy transplants, avoid fertilizer injury, and control insects to help reduce losses. Storing onions at 1°C (34°F) will help minimize losses. Resistance to Fusarium basal rot has been identified in some commercial onion cultivars.