Geotrichum sour rot

Geotrichum sour rot, caused by the fungus Galactomyces geotrichum (formerly Geotrichum candidum), is a significant post-harvest disease that affects a wide variety of fleshy fruits and vegetables. This pathogen is globally distributed and is particularly noted for its ability to cause rapid tissue decay in produce during storage and transit.

This disease primarily impacts crops such as sweet potatoes, tomatoes, citrus fruits, and various melons. The fungus thrives as a secondary invader, typically entering through skin punctures, insect damage, or natural growth cracks. Once inside, it utilizes enzymes to break down cell walls, causing the characteristic rapid collapse of plant tissue.

The symptoms of sour rot are distinct and include water-soaked, soft lesions on the surface of the produce. As the disease progresses, a white, velvety layer of mycelium develops over the decayed area. The common name "sour rot" is derived from the sharp, acidic odor that emanates from the infected tissue, which is a result of the fermentation process caused by the metabolic activity of the fungus.

Environmental conditions play a crucial role in the development and spread of this disease. Galactomyces geotrichum flourishes in high-humidity environments (above 90% relative humidity) and warm temperatures, typically ranging from 20°C to 30°C. In such conditions, the rot can spread rapidly from a single infected unit to the surrounding healthy produce through direct physical contact.

Management and prevention of sour rot focus on maintaining the physical integrity of the harvest and managing environmental factors during storage:

• Strict sanitation protocols in packing houses and storage facilities.
• Careful handling during harvest to minimize bruising and surface wounds.
• Removal of any infected or damaged produce prior to storage.
• Maintaining proper ventilation and climate control to prevent condensation on the crop.
• Sanitizing storage containers and equipment to reduce inoculum levels.