Phoma leaf spot

The disease known as Phoma leaf spot is caused by the fungus Boeremia coffeae. This fungal pathogen is a significant threat to coffee plantations worldwide, causing necrosis of leaves, stems, and berries. It is characterized by its ability to persist in plant debris, serving as a primary inoculum source for subsequent infection cycles during favorable weather conditions.

The primary host for Boeremia coffeae is the coffee plant, specifically species like Coffea arabica. The disease affects the productivity of the plants by damaging the photosynthetic tissue and causing dieback of terminal branches. If left unmanaged, the pathogen can severely reduce the total yield of a plantation by destroying flowers and young fruit buds.

Symptoms typically begin as small, dark brown or black lesions on the leaves, which expand and may develop a chlorotic halo. When the pathogen infects the branches, it causes depressed lesions that can eventually girdle the stem, leading to the death of the distal parts of the branch. Affected berries show dark sunken spots, making them unmarketable and susceptible to secondary infections.

The development and spread of Boeremia coffeae are strongly associated with high humidity, frequent rainfall, and moderate temperatures ranging from 18°C to 25°C. These conditions promote spore production and dissemination. Spores are primarily spread via rain splashes and wind, while human activity, such as pruning and harvesting, acts as a secondary vector for the pathogen.

Integrated management is essential for controlling this disease. Key strategies include:

• Regular pruning to remove infected plant parts and improve airflow.
• Proper canopy management to reduce micro-humidity around the foliage.
• Application of copper-based fungicides as a preventative measure.
• Sanitation protocols for tools used during pruning to prevent cross-contamination.

Successful control requires early detection and consistent maintenance of the plantation environment. By minimizing the moisture levels within the canopy and removing inoculum sources, growers can effectively mitigate the impact of this fungus on coffee production.