Mycena citricola

Mycena citricola is a phytopathogenic fungus belonging to the genus Mycena within the Mycenaceae family, Kingdom Fungi. This pathogen is best known for causing a specific disease in coffee trees (Coffea arabica), commonly referred to as "American leaf spot" or "Mycena leaf spot," affecting production in various tropical regions.

The disease manifests primarily through the appearance of circular, brown spots on the leaves, characterized by darker margins. As the infection progresses, these lesions expand and coalesce, frequently leading to premature defoliation. A distinct diagnostic feature, when humidity levels are high, is the development of tiny, delicate mushroom-like fruit bodies on the undersides of the infected leaves.

The biology of the pathogen is highly dependent on high atmospheric humidity and moderate temperatures, typical of high-altitude coffee-growing zones. The fungus spreads via spores, which are effectively disseminated by wind currents or splashing raindrops, allowing for rapid colonization of healthy leaf tissue when moisture is persistent.

The economic impact of Mycena citricola is primarily linked to the reduction of the photosynthetic surface of the coffee tree. This physiological stress leads to decreased vigor, reduced bean yield, and poor quality of the harvest. In severe outbreaks, the rapid loss of leaves significantly weakens the trees, making them susceptible to other stressors.

Recommended management and control practices include:

• Maintaining proper plantation spacing and canopy pruning to enhance air circulation.
• Implementing regular sanitation to remove and destroy infected foliage and plant debris.
• Applying preventive fungicide treatments, particularly those containing copper, during high-risk humid periods.
• Monitoring plantation microclimates to manage humidity levels effectively.