| CELERY
DISEASES |
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Leaf
Blights most important on celery are caused by two fungi: i) Cercospora
apii, ii) Septoria apiicola. Both fungi overwinter on and in affected
seed and in residue from diseased plants. Wet weather promotes fungus
reproduction. Splashing rain is important for the spread of Septoria,
whereas air currents are important for spread of Cercospora. Both
Septoria and Cercospora can be spread by movement of workers, animals,
and implements through fields.
Cercospora Blight
Septoria Blight |
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Black-Heart,
caused by calcium deficiency within the plants, affects center leaves.
The first symptom is water-soaked tips on the youngest leaves. These
areas turn brown and may enlarge untila ll leaves and petioles near
the center of the plant are affected. Black-heart results when insufficient
calcium is available to the plant. The disease appears to be promoted
by dry conditions and by potassium levels that are high in relation
to calcium levels. |
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Pink
Rot, caused by the fungus Sclerotinia sclerotiorum, describes
symptoms that develop on mature celery. In addition, the fungus causes
damping-off in infested seedbeds. The pink rot phase is characterized
by rapid development of basal crown and petiole rot. Plants appear
to suddenly wilt and collapse in the field. This rotted area is watery,
pinkish, and in moist conditions may become covered with a conspicuous
white mold which sometimes contains hard black clerotia (pea-sized
fungal reproductive structures). The sclerotia persist for many years
in soil. The disease develops best under moist conditions in cool
to moderate temperatures (up to about 77 ° F). |
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Bacterial
Soft Rot is caused by Erwinia carotovora and some other bacteria.
Affected areas appear water-soaked, develop a soft decay, and have
a distinctive foul odor. The bacteria usually infects plants through
wounds or other injured areas. Warm wet conditions promote disease
development. |
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Yellows,
caused by the fungus Fusarium oxysporum f. sp. apii, is characterized
by plant stunting and yellowing. Plants tend to be brittle and taste
bitter. Water conducting tissue, exposed by splitting the plants vertically
through the crown and petioles, may be yellowish-brown to red. As
the disease progresses crowns and roots may rot. Continuous celery
culture permits the fungus to build up in the soil. The disease is
most destructive during warm seasons. Yellows was an important celery
disease until resistant varieties became available in 1952. Recent
reappearance of the disease in California suggest development of a
strain of the fungus that can infect some varieties previously considered
resistant |
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Nematodes
(microscopic worms) may cause plants to be stunted, of poor color,
and prone to wilting during moisture stress. Above-ground symptoms
result from nematodes attacking the roots. Different nematodes cause
different root symptoms. Root knot nematodes (Meloidogyne spp.) cause
distinct swellings on the roots. Several other nematodes including
Pratylencush sp. and Paratylenchus sp. cause root stunting and discoloration.
Most nematodes can persist in soil for several years. Symptom severity
depends on nematode population levels in the soil, growing conditions,
and age of the plant. |
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Rhizoctonia
Stalk Rot, caused by Rhizoctonia solani, is characterized by
sunken, brick-red lesions on the stalks and at the base of plants. |
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Mosaic
can be caused by several viruses including cucumber mosaic virus (CMV)
and celery mosaic virus (CeMV). Symptoms caused by these two viruses
are similar and it may be difficult to distinguish the two diseases
on the basis of symptoms.
Cucumber Mosaic Virus
Celery Mosaic Virus
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