Charcoal rot (Macrophomina phaseolina)
Charcoal Rot (fungus - Macrophomina phaseolina). Many plants are susceptible to this soil borne fungus and symptoms vary according to type. Infected stem tissue shows evidence of shredding with tiny black dots (sclerotia) between the remaining tissues. This gives those plant parts an ashy-grey appearance. This can be observed by splitting the stalk and noting the deteriorated soft pith tissue leaving the tougher vascular strands. Fungal structures (sclerotia) can be observed in the affected tissue which appears as though it has been dusted with black pepper
Charcoal rot occurs most consistently when plants are experiencing moisture stress due to drought. The fungus is widely distributed and builds up in soil when susceptible host plants are present and conditions favour its development.
Avoiding moisture stress, proper management of crop residue, crop rotation, avoiding excessive plant populations, balancing nitrogen and potassium fertility levels, and growing drought-tolerant, lodging-resistant hybrids represent the best means of control.
- Rotate with unrelated crops (e.g. cereals) helps reduce the population of the fungus in the soil.
- Avoid moisture stress by increasing the moisture holding capacity of the soil and, if available, using irrigation when needed.
- Practices that hasten decomposition of crop residue may help decrease the population of the fungus in the soil.
