Symptoms and Signs
Celery is susceptible to the pink rot fungus at all stages of plant growth (including as transplants in trays), but the disease is most often observed on mature 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 inch long, may develop on diseased tissue. Under favorable conditions, 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.
Comments on the Disease
Sclerotia survive in the soil for prolonged periods without plant hosts. When cool, wet conditions occur, 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. Conditions that promote disease development are periods of prolonged wetness, excess moisture in heavy canopy, and fog.
Because many crops and weeds are hosts of this pathogen, spore releases may occur within and outside celery fields. Pink rot that occurs on celery transplants is caused by spores that blow into transplant facilities.
Management
Cultural Control
Crop rotation does not prevent pink rot but can reduce soil populations of the fungus. 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 Sclerotinia sclerotiorum.
Organically Acceptable Methods
Cultural controls are acceptable for use on organically grown produce.
Treatment Decisions
Directed sprays to the base of the plants may provide some protection against pink rot.
| Common name | Amount to use | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | DICLORAN | |||
| (Botran) 75W | 5.33 lb/acre | 12 | 28 | |
| MODE OF ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14) | ||||
| COMMENTS: Apply 4–8 weeks before harvest. Apply 1 application only at this rate. | ||||
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| 1 | Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of action. Fungicides with different group numbers are suitable to alternate in a resistance management program. In California, make no more than one application of a fungicide with a mode-of-action group number associated with high resistance risk before rotating to a fungicide with a different mode-of-action group number; for other fungicides, make no more than two consecutive applications before rotating to fungicide with a different mode-of-action group number. |