Pink Rot

Celery is susceptible to the pink rot fungus at all stages of plant growth, but the disease is most often observed on older plants when leaf canopies are well developed.

Initial symptoms appear as brown lesions on the petioles that develop at or near the soil line or up in the plant canopy. Lesions rapidly expand into soft, watery, decayed areas. The plant tissue surrounding the lesions may turn pink. In advanced stages of the disease, lesions may contain profuse white mycelia of the pathogen. Hard, black, irregularly shaped resting structures (sclerotia) ranging in size from 0.25 to 0.5 inches (6–12 mm) may develop on diseased tissue. Under conditions favorable to the pathogen, the entire petiole and plant base may collapse.

Leaf infections on newly forming leaves may also occur. Brown leaf lesions rapidly expand into the leaf petiole. As the leaf and petiole collapse, white mycelia and black sclerotia develop.

Celery plants in transplant trays are occasionally infected by the spore stage of S. sclerotiorum and therefore can develop leaf and stem rots in the trays; this phase of the disease is called white mold.

Sclerotia survive in the soil for prolonged periods without plant hosts. Under cool, wet conditions, sclerotia germinate and infect nearby plants at or below the soil surface. Alternately, sclerotia may develop spore-producing structures that release windborne spores. These spores may land on susceptible celery tissue and cause a canopy infection. Prolonged wetness, excess moisture in a heavy canopy, and fog promote disease development.

Transplanted celery crops that develop black heart, the calcium deficiency disorder, are very susceptible to infection by the aerial spores of S. sclerotiorum; these spores readily colonize the damaged new foliage in the plant centers.

Because many crops and weeds are hosts of this pathogen, spore releases may occur within and outside celery fields. S. sclerotiorum spores that blow into transplant facilities may cause white mold on celery transplants.

The other Sclerotinia species, S. minor, is the well-known lettuce-drop pathogen of lettuce. Celery can occasionally be infected with S. minor.

• Although crop rotation does not prevent pink rot, it can reduce the amount of fungal inoculum in the soil.
• Maintain adequate air movement within fields by proper plant and row spacing.
• Use drip instead of furrow irrigation.
• Do not use sprinkler irrigation, especially late in the crop cycle.
• Deep plowing or soil inversion does not reduce disease caused by S. sclerotiorum.

Use cultural controls in a certified organic crop.

Direct sprays toward the base of the plants to provide some protection against pink rot.