White root rot

White root rot, caused by the fungus Rigidoporus microporus, is a devastating disease affecting the root systems of various tropical perennial plants. This basidiomycete fungus acts as a necrotrophic parasite, effectively decaying woody tissues and killing host plants by severing their connection to water and nutrient absorption.

The disease is particularly notorious for damaging crops such as cassava (Manihot esculenta), rubber trees, cocoa, and coffee. The pathogen survives in the soil for several years, colonizing decaying organic matter and woody debris, which become the primary infection sources for new plantings.

Symptoms of the infection include yellowing of the foliage, sudden wilting, and subsequent death of the plant. Upon careful inspection of the root system, one can observe a dense white mycelial mat covering the roots, while internal root tissues often appear spongy, brittle, and exhibit signs of severe decay.

Disease development is favored by high soil moisture levels and warm tropical temperatures, typically between 25°C and 30°C. The infection spreads primarily through root-to-root contact, which is why the disease tends to develop in circular patches within an infected plantation.

Management strategies focus on strict sanitation, including the complete removal of stumps and roots before crop establishment. Key preventive actions include:

• Thorough clearing of infected wood debris from the soil.
• Creating deep trenches to isolate infected patches from healthy zones.
• Applying systemic fungicides to treat the soil near affected areas.
• Rotating crops with resistant species where possible.