Ophiobolus stem blight

Ophiobolus stem blight is a fungal disease caused by the ascomycete Ophiobolus acuminatus. While often acting as a saprotroph on decaying organic matter, this fungus can manifest as a serious parasite, attacking the stems of various crops and impairing their structural integrity and physiological health.

This pathogen demonstrates a wide host range, frequently affecting agricultural and wild species. The fungus persists within crop residues and soil, allowing it to remain in a field for several seasons if proper sanitation and rotation practices are not maintained, leading to a build-up of inoculum over time.

The visual symptoms of the disease include the development of dark, necrotic lesions on the stems. These lesions gradually enlarge and can encircle the stem, effectively blocking the transport of water and nutrients. As a result, affected plants show stunted growth, premature wilting, and are prone to lodging due to the weakened stem structure.

The infection is favored by high humidity and moderate temperatures, which are optimal for spore germination and colonization. Moisture serves as a key vector, with rain splashes and wind facilitating the spread of spores from infected plant debris to healthy stems, creating new infection points across the field.

Management strategies focus on reducing the initial inoculum and limiting the conditions for infection. Key practices include:

• Implementing crop rotation cycles to break the pathogen's life cycle.
• Effective tillage to bury infected plant residues.
• Application of targeted fungicides during favorable infection conditions.
• Ensuring proper field drainage to minimize humidity around the plant base.

Effective control is challenging once the disease has progressed into the late stages. Therefore, farmers should prioritize preventive agrotechnical methods, including the use of healthy certified seeds and field sanitation, to maintain a low disease pressure and ensure optimal crop yield potential.