Geotrichum rot

Geotrichum rot is a postharvest fungal disease caused by the pathogen Geotrichum citri-aurantii. Classified within the kingdom Fungi, this organism belongs to the genus Geotrichum. It is primarily known as a devastating agent of decay in various citrus species, including lemons, oranges, and grapefruit, often causing significant losses during storage, transit, and market distribution.

The primary symptom of this infection is a soft, watery rot on the rind of the fruit. As the disease progresses, a distinct white, velvety layer of mycelium and arthrospores covers the affected area. The tissue of the fruit rapidly degrades, becoming soft and mushy, often accompanied by a sour, fermentation-like odor. This deterioration makes the fruit completely unmarketable.

The life cycle of the pathogen is largely opportunistic, as it requires entry points to initiate infection. Mechanical injuries caused during harvesting, grading, or packing—such as small punctures, cuts, or abrasions—serve as the main pathways for infection. Once inside, the fungus thrives under warm, humid conditions, with optimal temperatures for growth typically falling between 20°C and 28°C.

The economic impact of Geotrichum rot is severe, primarily due to its rapid spread within storage containers. Once established in a single fruit, the fungus quickly spreads to adjacent healthy fruits through direct contact. This ability to trigger a "nest" of decay can compromise entire pallets or batches of citrus fruit within a few days if storage conditions are not strictly controlled.

Control and management of the pathogen focus on a combination of sanitation and postharvest treatments. Key strategies include minimizing fruit damage during handling to keep the rind intact, maintaining strict temperature controls to inhibit fungal metabolism, and performing regular sanitation of packing houses and storage crates. Additionally, the application of postharvest fungicides and specialized sanitizers remains a critical tool in managing the disease.