Stem rot (charcoal rot of bean) (Macrophomina phaseolina)
Initial symptom on stems and branches are spindle-shaped spots with light grey centres surrounded by brown margins. The centres of the spots have scattered dots (pycnidial bodies - fungal spores). The spots may join up and cause the branches or whole plants to dry up and die.
The fungus mainly attacks secondary finer roots. These roots have dark, blackened streaks underneath their barks with dots (pycnidial bodies - fungal spores).
Diseased plants suddenly wilt. When diseased plants are uprooted their roots are rotten and shredded. Disease development is favoured by hot dry weather (30 degC). Crops are more susceptible to the disease in the reproductive than in the vegetative stage.
- Use green manure.
- Use resistant or less susceptible varieties (e.g. red shelled varieties).
Macrophomina phaseolina
