Coffee cercospora leaf spot

Cercospora coffeicola is a fungal pathogen responsible for the disease known as "brown eye spot" or "cercospora leaf spot" of coffee. It is considered one of the most economically damaging fungal diseases affecting coffee plantations worldwide.

This fungus attacks both the leaves and the coffee cherries. While leaf infection causes defoliation and reduces the photosynthetic capacity of the tree, fruit infection results in the "black bean" defect, which significantly downgrades the quality of the harvested coffee beans.

Symptoms are identified by circular spots with a dark center and a yellow or pale halo. On the berries, the spots appear as dark, sunken lesions that may eventually cover the entire surface, leading to premature berry drop or drying of the fruit tissue on the branches.

The development of the fungus is highly dependent on environmental conditions, specifically high humidity and temperatures between 20°C and 25°C. It spreads via wind-borne conidia and splashing rain. Poorly managed plantations with dense canopies and high shade density are particularly susceptible.

Effective disease management requires a combination of cultural and chemical strategies. Key practices include improving orchard sanitation, maintaining optimal plant nutrition, and strategic pruning to increase air circulation. Fungicide applications should be timed correctly based on regional disease forecasting systems.