Ratoon stunting disease

Ratoon stunting disease is caused by the Gram-positive bacterium Leifsonia xyli subsp. xyli. This pathogen is a highly specialized colonizer of the plant vascular system, specifically the xylem elements, where it accumulates in significant densities and interferes with hydraulic conductivity.

The primary host for this bacterial pathogen is sugarcane. The disease is named for its ability to persist and spread within the ratoon crops—the regrowth from the stubble remaining after harvest. The infection is primarily systemic, spreading through both the use of infected vegetative cuttings and the mechanical transmission via contaminated tools.

The visual symptoms of the disease are often subtle, which poses a significant challenge for field identification. Infected plants typically exhibit reduced growth vigor, shorter internodes, and smaller canopy size compared to healthy sugarcane. A definitive internal sign is the discoloration of the nodal vascular tissue, often appearing as a pinkish or reddish tint when the stalk is cut.

The development and dissemination of the disease are highly dependent on the efficiency of mechanical transmission. While environmental factors like humidity influence the host health, the primary driver for spread is the lack of sanitation during the harvesting process. The pathogen remains viable in cane sap, allowing it to move rapidly across a field via cutting blades.

Economic damage is substantial, manifesting as lower crop yield and reduced sugar content in the stalks. Effective management and prevention programs should focus on:

• Planting healthy, pathogen-free seed cane.
• Hot water treatment of planting material to eliminate bacteria.
• Rigorous disinfection of mechanical harvesting equipment.
• Implementation of resistant cultivars to minimize susceptibility.