Green mold of citrus

The pathogen Penicillium digitatum is the primary cause of green mold, representing the most significant postharvest disease affecting citrus fruits globally. It is an opportunistic fungus that primarily targets fruits that have sustained physical injuries during harvesting or post-harvest handling, making it a critical concern for agricultural logistics.

This fungus affects virtually all citrus cultivars, including oranges, lemons, mandarins, and grapefruits. While the outer peel of a healthy, undamaged fruit provides a degree of resistance, any break in the rind—such as a scratch, puncture, or stem-end tear—allows the fungal spores to enter the fruit tissue and initiate the rotting process.

Symptoms initially appear as soft, watery, pale spots on the surface of the fruit. Within a short period, these spots expand, and a white mycelial mat develops. As the fungus produces massive amounts of conidia, the surface turns a distinct olive-green color, which is the hallmark diagnostic feature of this specific disease.

The development of the disease is highly favored by temperatures ranging from 20°C to 25°C and high relative humidity levels. Penicillium digitatum spores are extremely buoyant and prolific, quickly contaminating the air of packinghouses and storage facilities, thereby ensuring a constant reinfection cycle if sanitation measures are ignored.

• Handle fruit with extreme care to avoid peel injuries.
• Apply postharvest fungicides approved for citrus protection.
• Maintain strict temperature control, ideally keeping storage below 5°C.
• Implement rigorous sanitation protocols for sorting machinery and storage boxes.
• Regular inspection and removal of infected fruits to prevent contact spread.

The economic impact of green mold is severe, as it is a leading cause of postharvest loss in the citrus industry. Because the disease spreads through contact, known as "nesting," a single decaying fruit can compromise an entire shipping crate or pallet within days, leading to massive financial losses and reduced product quality.