GROUNDNUT :: MAJOR DISEASE :: ROOT ROT

Root rot - Macrophomina phaseolina
Symptoms
In the early stages of infection, reddish brown lesion appears on the stem just above the soil level. The leaves and branches show drooping, leading to death of the whole plant. The decaying stems are covered with whitish mycelial growth. The death of the plant results in shredding of bark. The rotten tissues contain large number of black or dark brown, thick walled sclerotia. When infection spreads to underground roots, the sclerotia are formed externally as well as internally in the rotten tissue. Pod infection leads to blackening of the shells and sclerotia can be seen inside the shells.
Pathogen
The fungus produces hyaline to dull brown mycelium. The sclerotia are thick walled and dark brown in colour.
Favourable Conditions

• Prolonged rainy season at seedling stage and low lying areas.

Disease cycle
The fungus remains dormant as sclerotia for a long period in the soil and in infected plant debris. The primary infection is through soil-borne and seed-borne sclerotia. The secondary spread of sclerotia is aided by irrigation water, human agency, implements and cattle etc.
Management

• Treat the seeds with thiram or carbendazim 2g/kg or Trichoderma viride at 4g/kg.
• Spot drench with Carbendazim at 0.5 g/lit.