Rhizopus microsporus

Rhizopus microsporus is a fungal pathogen belonging to the Zygomycota phylum. It is known as the causative agent of rhizopus rot, a destructive disease affecting various plant tissues both in the field and during post-harvest storage. Its biological nature allows it to grow rapidly in nutrient-rich plant substrates.

The host range of Rhizopus microsporus is exceptionally broad, including oilseeds like sunflower, various vegetable crops such as tomatoes and cucumbers, as well as soft fruits. It is particularly notorious for damaging produce in warehouses, where it can spread through contact, turning bulk commodities into rotted piles.

Symptoms of the infection typically present as a dense, fuzzy, grayish-brown mycelial mat developing on the surface of the plant tissue. As the fungus secretes digestive enzymes, the affected plant parts lose structural integrity and become soft, watery, and mushy, eventually covered by dark sporangia clusters.

Development and spread are strongly favored by high ambient temperatures (often 25°C to 30°C) and high humidity levels. The pathogen primarily gains entry through mechanical wounds, insect punctures, or bruises caused during harvest. High density in storage environments further exacerbates the spread of the fungus.

The economic impact of this fungus is significant due to its rapid destruction of produce. Beyond immediate weight loss and market value reduction, Rhizopus microsporus can produce secondary metabolites or mycotoxins, which poses health risks and renders the infected produce unsafe for animal or human consumption.

Key strategies for management and prevention include:

• Implementing strict sanitation practices in both fields and storage facilities.
• Ensuring proper ventilation to maintain low humidity levels during storage.
• Managing insect populations to prevent entry points for the pathogen.
• Handling crops carefully during harvest to avoid mechanical damage.
• Using appropriate fungicides as a preventive measure in high-risk environments.