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Late blight of potato

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Late blight of potato

  1. 1. Late Blight of Potato
  2. 2. Late Blight of Potato Description: • This disease caused by fungus called Phytophthora infestans. • The disease may attack almost any time after the crop has put up a fairly good foliage. • Initially the lower leaves infected.
  3. 3. Late blight Phytophthora infestans • Irish famine - 1845-46 Symptoms • 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
  4. 4. • In tubers - purplish brown spots & spread to entire surface • Tuber show rusty brown necrosis spreading from surface to the center
  5. 5. 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 15oC) and humid ( above 90 %) weather with rains alternating with warm (20o C) moist period
  6. 6. Fungus  Mycelium - endophytic, coenocytic and hyaline  Sporangiophores – arise from internal mycelium through stomata on the tubers  Sporangia - multinucleate, thin walled, hyaline, oval shaped  Zoospores - biflagellate Phytophthora infestans A, zoospores produced within the lemon-shaped sporangia (B).
  7. 7. Control measures  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)

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