Black root

Black root, caused by the fungus Rosellinia bunodes, is a severe soil-borne disease that affects the root systems of various crops. As a necrotrophic pathogen, it colonizes the roots and root collar, causing tissue decay and leading to plant wilting and rapid death.

The pathogen has a wide host range, posing a significant threat to crops such as cacao, winter oilseed rape, Indian mustard, radish, and turnip. Its ability to persist in the soil for extended periods makes it a persistent challenge in both tropical and temperate agricultural zones.

Infected plants typically show early signs of drought stress, followed by yellowing and necrosis of the leaves. A diagnostic feature is the presence of black, rhizomorph-like mycelial mats on the roots, which gradually destroys the bark and prevents the transport of water and nutrients throughout the plant.

The development of Rosellinia bunodes is highly dependent on environmental conditions, particularly high soil moisture and warm temperatures. The fungus spreads through the soil by contact between healthy and infected root systems and is often exacerbated by poor field drainage and sanitation.

Management strategies must focus on prevention and sanitation. Crucial measures include removing infected plants along with surrounding soil, ensuring proper soil aeration, and maintaining a rigorous crop rotation to break the pathogen's life cycle. Chemical treatments can be used in nurseries, but cultural practices remain the primary line of defense.

• Sanitary removal of infected host material
• Improved field drainage systems
• Crop rotation with non-host species
• Site sanitation to prevent spread