Late blight of celery

Late blight of celery, also known as Septoria leaf spot, is a destructive fungal disease caused by the pathogen Septoria apiicola. This disease is a significant limiting factor in celery production globally, capable of causing total crop failure if management practices are neglected during favorable weather conditions.

The disease primarily affects Apium graveolens. The pathogen thrives by infecting the foliage and petioles, leading to premature leaf senescence. It is a seed-borne pathogen, which means the initial inoculum can be introduced into the field directly through infected seeds, making high-quality seed certification essential.

Early symptoms appear as small, chlorotic spots on leaves, which gradually turn brown and necrotic as the disease progresses. A diagnostic feature is the presence of numerous tiny, black pycnidia (fruiting bodies) embedded within the lesions. If conditions remain wet, these spots coalesce, causing leaves to wither and die.

The spread of Septoria apiicola is heavily dependent on moisture. Spores are splashed by rain or irrigation water and carried by wind to healthy tissues. The fungus prefers cool to moderate temperatures and high humidity, often peaking during periods of prolonged rainfall, which allows the disease to spread rapidly through a crop field.

Effective management relies on a combination of cultural and chemical controls. Growers should focus on using pathogen-free seeds, practicing a strict three-year crop rotation, and removing volunteer celery plants. In areas with high disease pressure, regular applications of protective and systemic fungicides are necessary to maintain crop health.

• Use of certified, disease-free seeds.
• Deep plowing to bury infected plant residues.
• Adequate spacing to ensure proper air circulation.
• Avoidance of overhead irrigation where possible.
• Application of preventative fungicides during wet weather.