Cassava bacterial wilt

The causative agent is Xanthomonas cassavae, a gram-negative rod-shaped bacterium that acts as a serious vascular pathogen. It disrupts the plant's nutrient transport system by colonizing the xylem, leading to severe physiological stress and systemic wilting. This bacterium is recognized as a major threat in tropical agricultural landscapes.

The primary crop affected is cassava (Manihot esculenta). As a staple food for millions, the impact of this disease on cassava yields is a significant agricultural concern. Both vegetative growth and the development of edible tuberous roots can be severely compromised by the infection, leading to substantial crop losses.

Symptoms initially appear as water-soaked, angular spots on leaves, which gradually develop into necrosis. As the disease advances, the vascular bundles become blocked, leading to shoot wilting, systemic necrosis, and the presence of bacterial exudate on stems. If left unmanaged, the entire plant structure degrades rapidly.

The development and spread of Xanthomonas cassavae are highly dependent on high moisture levels and warm temperatures. Rain-splash and wind are primary vectors that move the bacteria from infected to healthy tissues. Furthermore, human activity, including the movement of contaminated farm tools and infected propagation materials, facilitates long-distance spread.

Effective management requires an integrated approach to reduce bacterial pressure:

• Selection of disease-resistant varieties and cultivars.
• Propagation using only certified, pathogen-free planting materials.
• Strict sanitation protocols for farm equipment and tools.
• Implementation of crop rotation cycles to break the pathogen's life cycle.
• Prompt removal and destruction of symptomatic plants to limit spread.