Late Blight of Celery

Late Blight of celery is caused by Septoria apiicola and is the most important foliar disease of celery throughout the world. The disease is capable of causing severe crop losses under favorable conditions of warm, wet weather.

Symptoms appear on older leaves first as small, irregular, chlorotic lesions. Leaf spots quickly enlarge and become brown and necrotic with numerous black, fruiting bodies (pycnidia) embedded in the tissue. Leaf spots can coalesce and result in blighting and leaf death. Petioles are also subject to infection and develop grayish-brown, irregular lesions with numerous pycnidia. If the crop is exposed to rain or overhead irrigation, the disease can spread very rapidly. The pathogen survives on the seed and in infested crop debris. Disease development is favored by a dense plant canopy and long periods of leaf wetness.

Management:

• Start with certified, disease free seed or treat seed with fungicides (thiram).
• Inspect transplants and discard symptomatic plants.
• Start with pasteurized soil or potting mixes.
• Rotate out of celery for two years.
• Do not work in fields when plants are wet.
• Avoid overhead irrigation and use drip or in-furrow irrigation.
• Destroy volunteer celery plants.
• Apply protectant fungicides on a regular schedule when disease pressure is high. Registered fungicides include azoxystrobin (Quadris), chlorothalonil (Bravo), copper (Kocide), and propiconazole (Tilt).