Charcoal rot

Charcoal rot is a destructive plant disease caused by the soil-borne fungus Macrophomina phaseolina. It is a cosmopolitan pathogen known to infect over 500 species of plants, with significant economic impact on major crops such as sunflower, soybean, corn, and sorghum worldwide.

The fungus survives in the soil and on infected plant debris primarily as microsclerotia. These dormant structures can persist for several years, making the pathogen difficult to eradicate. Infection typically initiates in the root system as seedlings or mature plants encounter favorable environmental conditions for fungal growth.

Symptoms of charcoal rot often become apparent during reproductive growth stages, especially during moisture stress. The most characteristic sign is the presence of minute black microsclerotia within the cortical tissues of the stem and roots, giving the infected parts a charred or ashy appearance. Infected plants exhibit chlorosis, premature wilting, and eventual death.

The development of the disease is heavily influenced by environmental factors, particularly high soil temperatures (between 28°C and 35°C) and low soil moisture. Drought stress severely compromises the plant’s natural defenses, allowing the fungus to colonize the vascular tissues rapidly and disrupt the uptake of water and nutrients.

Effective management requires an integrated approach. Farmers should implement long-term crop rotation cycles, avoiding the cultivation of highly susceptible hosts in short intervals. Improving soil water-holding capacity through irrigation and proper residue management is essential. Additionally, planting resistant or tolerant varieties remains the most cost-effective long-term strategy for minimizing yield losses.