Grey spot of citrus

The disease is caused by the fungus Zasmidium citri-griseum. It is a significant phytopathogen that affects citrus foliage, causing premature defoliation and a decline in the overall vigor of the trees, which impacts fruit production.

This pathogen specifically attacks various citrus species including lemons, oranges, and grapefruits. It is particularly problematic in commercial orchards where high-density planting and environmental conditions provide the perfect habitat for the fungus to thrive.

Symptoms appear as small yellow to brown spots on the leaf surface, which eventually turn grey. This color change is due to the dense development of fungal spores on the underside of the leaf, which interferes with respiration and photosynthetic processes.

Disease progression is highly dependent on environmental conditions, particularly high humidity and warm temperatures. The spores are primarily dispersed through rain splash and wind, allowing the fungus to rapidly colonize the foliage during the growing season.

Economic damage includes reduced tree yield and poor fruit development. Management strategies involve regular pruning to improve airflow, sanitation measures to remove infected leaf litter, and the application of copper-based fungicides or systemic chemical treatments.