Sarocladium sheath rot

Sarocladium sheath rot is a severe fungal disease affecting rice crops, caused by the pathogen Sarocladium oryzae. This disease is particularly prevalent in humid tropical and subtropical environments where rice is grown under intensive irrigation systems.

The primary crop affected is rice (Oryza sativa). The disease attacks the leaf sheath that encloses the developing panicle. The economic impact is significant, as severe infections can lead to total crop failure, sterile grains, and lower yields, causing substantial losses for farmers globally.

Symptoms appear as oblong or irregular lesions on the leaf sheaths, initially gray with a dark reddish-brown border. As the infection progresses, a white, powdery mass of fungal mycelium and spores develops inside the sheath. This prevents the panicle from emerging properly, leading to partial or complete rot of the developing grain structures.

The development of the disease is favored by high humidity (85% or higher) and temperatures between 25°C and 30°C. The pathogen persists in soil, infected plant residues, and is often seed-borne. Furthermore, rice-infesting insects often act as vectors, causing mechanical injuries that facilitate the colonization of the fungus into the plant tissue.

Effective management requires a multi-faceted approach aimed at reducing the inoculum level and limiting the spread of the fungus.

• Utilization of resistant or tolerant rice varieties.
• Implementation of balanced fertilization programs, avoiding excessive nitrogen applications.
• Field sanitation, including the removal and burning of infected crop debris.
• Application of systemic fungicides during the boot leaf stage when conditions are conducive to infection.