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Tobacco Damping off – Kisan Suvidha
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Tobacco Damping off

Tobacco Damping off

Tobacco Damping off: ythium aphanidermatum, Pythium debaryanum

Symptom:
  • Damping off is a serious problem in tobacco nurseries both in heavy clay soils and light sandy soils.
  • It is caused by some soil inhabiting fungi predominant being Pythium aphanidermatum, pythium debaryanum,Phytophthora sp. and some times Rhizoctonia solani are also involved.
  • The disease may appear at any stage of the seedlings but the maximum damage is observed 5-6 weeks after sowing.
Disease is noticed in two phases, viz.
  1. Pre-emergence damping-off
  2. Post-emergence damping-off
Pre-emergence damping-off
  • Seedlings are infected which die before emergence from the soil resulting in poor and uneven stand of the seedlings
Post-emergence damping-off
  • Post emergence damping- off is the most destructive phase.
  • The tiny two leaved seedlings may disappear due to wet rotting of stems and the seedlings stand diminishes daily.
  • Generally, damping-off occurs in patches which spread quickly if unchecked.
  • The older seedlings show shrivelling and brown discoloration of the stems near the soils and start rotting under wet soil conditions.
  • The decayed stems collapse and seedlings topple over leaving parchment like brown crest over the soil.
  • The wet rotting and sudden collapse of seedlings start in circular patches and under wet weather conditions may extend over the whole seedbed causing near total loss.
Management:
  • Deep ploughing in summer destroys the fungus
  • Preparation of raised seed beds 15 cm high with channels around to provide drainage
  • Rubbing the seed bed before sowing with slow burn farm waste materials like paddy husk, tobacco stubbles, waste grass and Palmyra leaves etc.,
  • Use seed rate 3 g/ha only to avoid over crowding of seedlings.
  • Regulate waterings to avoid excessive dampness on the bed surface.
  • Bordeaux mixture 0.4% @ (40 gm of copper sulphate + 40gm of lime in 10 litres of water) or Copper oxychloride @ 0.2% (20 gm in 10 litres of water) is to be applied with rose can to a bed of 10 sq.m area 2 weeks after sowing.
  • Two to three spray drenchings of beds with 0.2% Metalaxyl commencing three weeks after seed sowing (20 g of Metalaxyl in 10 l of water).
  • This has to be repeated once in 4 days under normal weather conditions and once in 2 days under wet and cloudy conditions. In the case of heavy rain, the application has to be repeated.
Schedule of application
  • Application of fungicide should be given one week after completion of germination.
  • Subsequent application, depending upon weather conditions, should be given at 4 days interval if it is bright, sunny and dry, and 2 days when it is the cloudy and wet weather. The application should be repeated after every rain.
  • Approximately 40 litres of spray fluid for 40 m2 of seedbeds, applied through a rose-can or 20 litres through knapsack sprayer is required for each application.

 

 

Source-

  • TamilNadu Agritech Portal

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