Rigidoporus zonalis

Rigidoporus zonalis is a destructive basidiomycete fungus known to cause white root rot in various woody plant species. As an aggressive pathogen, it specializes in the decomposition of lignin, which leads to the structural failure of the plant's root system and eventually results in the total decline of the host organism.

The host range of this fungus is extensive, covering critical tropical and subtropical crops, including rubber trees, tea plantations, cocoa, and various fruit-bearing orchard trees. Due to its saprotrophic and parasitic capabilities, it can persist in the soil for several years by colonizing dead organic matter and root debris.

Visual signs of infection include stunted growth, chlorosis, and the progressive wilting of the foliage, which often precedes tree death. A definitive diagnosis is typically made by observing the presence of distinctive white mycelial mats or cord-like rhizomorphs on the roots. Internally, the infected wood displays a characteristic zonal discoloration, marking the transition between sound and decayed tissues.

The development of the disease is heavily influenced by soil moisture levels and existing root injuries caused by agricultural practices or soil-dwelling pests. The fungus spreads primarily through root-to-root contact, as the rhizomorphs extend through the soil to reach adjacent healthy trees, making the disease difficult to contain once it has established in a plantation setting.

Integrated disease management is essential to mitigate the impact of Rigidoporus zonalis. Key control strategies include:

• Thorough removal of stumps and infected root fragments from the field.
• Digging isolation trenches around infected areas to prevent the spread of rhizomorphs.
• Improving soil drainage and overall tree vigor through balanced nutrition.
• Application of prophylactic fungicides and biological control agents to the soil environment.