Rice stem rot

Rice stem rot is a fungal disease caused by the pathogen Nakataea oryzae (teleomorph Magnaporthe salvinii). This disease is globally significant, causing substantial yield losses in rice-producing regions by weakening the culm structure of the rice plant and leading to severe lodging before harvest.

The disease specifically impacts Oryza sativa and related species. It begins by colonizing the leaf sheaths near the water line, eventually progressing to the internal stem tissues. As the fungus consumes the culm's structural integrity, the plant becomes unable to transport nutrients effectively to the panicles.

Symptoms initially appear as small, irregular black spots on the outer leaf sheaths. As the infection deepens, these spots enlarge and become greyish-black. Inside the stems, the fungus produces numerous dark, small sclerotia. These structures are essential for the pathogen's survival and are the primary source of primary infection in subsequent growing seasons.

The development of Nakataea oryzae is highly dependent on environmental conditions, particularly high humidity and water temperatures between 20°C and 30°C. Poor water management in paddies, such as maintaining stagnant, nutrient-rich water for extended periods, significantly increases the risk of infection outbreaks within a field.

Integrated pest management is crucial for mitigation:

• crop rotation with non-host plants;
• balanced fertilization to avoid excessive nitrogen;
• thorough post-harvest destruction of crop residues;
• application of effective fungicides at the tillering and heading stages.