Absidia

Absidia (genus Absidia) is a genus of filamentous fungi belonging to the order Mucorales. These organisms are classified as opportunistic pathogens. While many species are well-known saprobes found in soil and decaying organic matter, several species act as significant plant pathogens, causing soft rot and various forms of decay in both field crops and stored agricultural produce.

The fungus affects a diverse range of crops, including vegetables, fruits, and tubers. The primary diseases caused by Absidia involve soft tissue necrosis. Affected plant parts quickly lose their structural integrity, becoming watery and soft. A dense, rapidly growing mycelium—initially white and later turning greyish—often covers the affected area, indicating the sporulation phase of the fungus.

The biology of Absidia is characterized by prolific and rapid spore production within specialized structures called sporangia. These spores are easily disseminated by air currents, splashing water, and insect vectors. Because the fungus is highly adaptive, it can survive in the soil for extended periods in the form of resting spores or dormant mycelium, waiting for favorable environmental conditions to colonize new plant tissues.

Development and spread are heavily influenced by environmental stressors. High humidity (often above 85%) and warm temperatures are critical for the rapid germination of spores and the subsequent colonization of host tissues. Mechanical injuries, such as cuts from harvesting tools or lesions caused by pests, serve as primary entry points for the pathogen, significantly increasing the risk of infection.

Effective management and control of Absidia require a focus on hygiene and environmental manipulation:

• Remove and destroy all infected plant material from the fields.
• Minimize mechanical damage to fruits and vegetables during harvesting and transport.
• Maintain strictly controlled humidity and temperature levels in storage facilities.
• Ensure adequate ventilation in greenhouses to prevent localized humidity spikes.
• Apply preventative fungicide treatments when environmental conditions favor fungal outbreaks.