Cercospora leaf blight of celery

The causative agent of this disease is the fungus Cercospora apii, which belongs to the class of Hyphomycetes. This pathogenic fungus specifically targets members of the Apiaceae family, with celery being the primary host. The disease is known for causing severe defoliation and reduction in the overall quality and marketable yield of the crops.

The disease primarily affects various types of celery, including celeriac, leaf, and stalk celery. The pathogen is highly persistent, capable of surviving for long periods as mycelium in infected plant debris left in the soil or carried on and within contaminated seeds, which often serves as the primary inoculum for the next growing season.

Initial symptoms include the appearance of small, circular to irregular lesions on leaves and petioles that start as yellow spots and eventually turn brown with a dark border. Under high humidity, a grey, fuzzy growth consisting of fungal conidia develops in the center of these lesions. As the infection progresses, spots coalesce, causing leaves to wither, turn necrotic, and drop off.

The spread of Cercospora apii is heavily influenced by environmental conditions, specifically temperatures between 20°C and 28°C and high relative humidity. Frequent rainfall and overhead irrigation facilitate the dispersal of spores via splashing water droplets. Furthermore, the fungus can be spread by wind, insects, and human activity within the field.

• Practicing strict crop rotation, ensuring a gap of at least three years between susceptible crops.
• Using high-quality, certified, and disease-free seeds or treated seed lots.
• Removing and destroying all plant residues after harvest to reduce pathogen overwintering.
• Application of preventative and systemic fungicides when weather conditions favor disease development.

The economic impact of cercospora leaf blight is significant, as it leads to reduced photosynthetic capacity of the plants, resulting in stunted roots and diminished stalk growth. In severe cases, the entire crop may become unmarketable. Integrated pest management, focusing on sanitation and moisture control, is essential for maintaining crop health and productivity.