Citrus zonate spot

Citrus zonate spot is a fungal disease caused by species of the Fusarium genus that affects various citrus fruits. The disease is notorious for its ability to cause rapid decay in harvested fruits, leading to significant economic losses in the citrus industry, particularly in humid regions.

This condition primarily impacts commercial citrus species, including lemons, oranges, and grapefruits. The pathogen is opportunistic, meaning it often targets weakened fruit or fruit that has been exposed to high humidity and favorable thermal conditions during the maturation phase in the orchard.

The characteristic symptom of this disease is the appearance of brownish, concentric, ring-like spots on the rind of the fruit. As the infection progresses, the tissues within these zones soften, often developing a white or pinkish moldy appearance, which is the result of the fungus producing spores on the surface of the fruit.

Development and spread are heavily dependent on environmental conditions. Rain and irrigation splashes facilitate the dispersal of spores from the soil or infected debris onto the lower-hanging fruits. Once the fungal spores germinate, they penetrate the rind through lenticels or micro-wounds caused by mechanical damage, insects, or environmental stress.

Effective management requires an integrated approach. Prevention strategies include keeping the orchard clean to reduce inoculum levels, pruning trees to improve ventilation and reduce humidity within the canopy, and ensuring careful harvesting techniques to prevent rind injury. In severe cases, preventive applications of copper-based fungicides during the fruit-set period are recommended.