How to Manage Pests

UC Pest Management Guidelines

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	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
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 (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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 actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.

PUBLICATION

UC IPM Pest Management Guidelines: Celery
UC ANR Publication 3439
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
R. M. Davis, Plant Pathology, UC Davis
T. A. Turini, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Diseases:
R. L. Gilbertson, Plant Pathology, UC Davis
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara County

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