• Leaves, stems and tubers
• Water soaked spots appear on leaves, turn purple brown & finally black colour
• White growth develops on under surface
• Stem breaks at these points and the plant topples
• In tubers - purplish brown spots & spread to entire surface
• Tuber show rusty brown necrosis spreading from surface to the center

Identification of pathogen:

• Mycelium - endophytic, coenocytic and hyaline
• Sporangiophores – arise from internal mycelium through stomata on the tubers
• Sporangia - multinucleate, thin walled, hyaline, oval shaped
• Zoospores - biflagellate

Mode of spread and survival:

• Infected tubers and infected soil - source of primary infection
• Survival of fungus in fruiting stage or as dormant mycelium  in the soil
• Persisting of perennial mycelium in affected tubers from the field, stored and used as seed in next season

Epidemiology:

• Cool (12 to 15°C) and humid ( above 90 %) weather with rains alternating with warm (20°C) moist period 

• S. demissum and S. phureja - used for breeding for disease resistant varieties
• Varieties - Kufri Naveen, Kufri Jeevan, Kufri Alenkar, Kufri Moti
• Bruising of tubers at harvest should be avoided
• Regular spraying during growing season gives effective control- 10 to 15 days interval
  • Brestan 600g/ha
  • Zineb 0.2 %
  • Bordeaux mixture 1.0%
  • Mancozeb (2 kg/ha)