Alternaria leaf spot of chicory

The disease is caused by the fungus Alternaria cichorii, a common plant pathogen known for inducing necrotic leaf spots. This fungus is highly specialized, primarily targeting members of the Asteraceae family, and it functions by secreting toxins that break down plant cell walls.

The primary host for this pathogen is chicory, including both leaf and root varieties. Due to the high host specificity, the presence of the pathogen in areas with continuous cropping of chicory can lead to severe annual outbreaks, significantly impacting agricultural yield and commercial product quality.

Infection begins as small, water-soaked spots on the leaves, which gradually darken to brown or black. A key diagnostic feature is the development of concentric rings within the lesion, resembling a target pattern. During high humidity, a velvety layer of spores appears on the surface, which is easily detached and wind-dispersed.

Conditions favorable for the development of the disease include high relative humidity, frequent rainfall, and temperatures between 20°C and 25°C. Water droplets on foliage are essential for spore germination and infection. The pathogen persists in soil, crop debris, and can be seed-borne, allowing it to survive between growing seasons.

The economic impact of the disease is significant, as it leads to defoliation and reduced photosynthetic capacity of the plant. This loss of foliage directly results in lower root weight, reduced sugar content in industrial chicory, and poor storage quality, ultimately threatening the profitability of the harvest.

• Regular field scouting to detect early signs of fungal lesions.
• Application of appropriate fungicides when weather conditions promote fungal spread.
• Removal and deep burial of post-harvest crop debris to reduce inoculum levels.
• Implementation of a 3-to-4-year rotation cycle excluding other Asteraceae crops.