Nigrospora ear rot

Systematic position and nature of the pathogen: Nigrospora oryzae belongs to the kingdom Fungi, division Ascomycota, and the genus Nigrospora. It is a cosmopolitan fungus often identified as a facultative parasite or a saprotroph, causing secondary infections in various agricultural crops worldwide.

Diseases and host crops: The fungus causes a disease known as nigrospora ear rot or black rot. While it is primarily recognized for infecting rice (Oryza sativa), it also affects other economically significant crops such as maize, sorghum, and cotton. Infection is typically characterized by the presence of dense black, velvety spore masses on affected plant parts.

Biology and life cycle: The pathogen reproduces via conidia, which are efficiently dispersed by wind, water splashes, and insects. It overwinters as mycelium or spores within infected plant debris in the soil or in stored seeds. Infection occurs when environmental conditions favor the germination of conidia, allowing the hyphae to penetrate plant tissues.

Conditions for development and harmfulness: Nigrospora oryzae thrives in environments with high humidity (above 85%) and warm temperatures ranging from 25°C to 30°C. The fungus causes significant damage by infecting the grain, leading to poor seed set, low germination rates, and severe quality degradation, which can result in substantial yield losses during favorable infection periods.

Control and management measures: Effective management requires an integrated approach to minimize the primary inoculum and protect susceptible crops:

• Planting certified, pathogen-free seeds to ensure initial field health.
• Implementing crop rotation to break the survival cycle of the fungus.
• Sanitation practices, including the removal and destruction of crop residues.
• Applying systemic fungicides as seed treatments or foliar sprays when environmental conditions trigger high disease pressure.
• Optimizing crop nutrition to ensure plant vigor and minimize susceptibility to secondary pathogens.