Sour rot

Sour rot is a destructive plant disease caused by the fungus Geotrichum candidum. It is a soil-borne pathogen that thrives as a saprophyte but can act as a serious parasite, causing rapid decay in various agricultural and horticultural products worldwide.

The pathogen has a wide host range, primarily infecting Citrus species, peaches, grapes (Vitis vinifera), and various vegetables such as tomatoes and carrots. It is particularly devastating during the ripening stage and throughout the post-harvest storage phase.

The symptoms of infection include the appearance of soft, watery lesions that expand rapidly across the fruit tissue. A distinguishing characteristic of sour rot is the sharp, acidic odor of fermentation accompanied by a visible white or creamy-colored mycelial growth on the surface.

The development of the disease is favored by high temperatures (optimally between 25°C and 30°C) and high humidity levels. The fungus typically enters the host tissue through mechanical wounds, cracks caused by rapid growth, or punctures caused by insects, leading to quick tissue colonization.

The damage caused by sour rot is severe, often leading to total loss of marketability within days if conditions are optimal for the fungus. It creates a soft, mushy rot that renders the fruit inedible, often complicating storage and international trade of fresh produce.

Effective management and prevention strategies include the following practices:

• Strict field hygiene and the removal of decaying plant debris.
• Integrated pest management to control insects that wound fruit skins.
• Gentle harvesting and handling practices to prevent bruising.
• Maintaining proper temperature and humidity control in storage facilities.
• Judicious use of chemical control methods approved for specific crops.