Practical Exposure Of Late Blight Disease Of Potato Caused By Phytophthora Species And Demonstration Of Its Management At Ucbms&H, Dehradun By Agriculture Students

Brief history of disease:
Destructive, late blight disease of potato was first of all discovered by Anton de Bary during the year, 1876. On account of this disease famine resulted in Ireland during the year, 1845-46 and even today the disease is known as Iris blight disease. The disease is prevalent in all the potato growing areas.

It is worth wile to mention that main food stuff of Ireland and Europe’s people in those days was potato and for about 200 years people of that geographical area were dependent only on potato. At that time due to destruction of complete crop approximately (1,000,000) people died due to hunger and approximately 15, 00,000 people left the Ireland and settled in Canada and America.

Disease Identification Symptoms:-

  • Disease symptoms appear at the flowering stage of the potato crop.
  • First of all irregular of circular spot of light yellow in colour or water soaked spot appear on the lower leaf surface of the plant and either these symptoms start to appear from the tip or margin of the leaf and spread towards the center of the leaf.
  • In moist weather conditions these symptoms spread very fast on the leaf surface and covered most of the part of leaf as brownish spot and later on converted into brownish black or violet lesions but in dry weather the spot remains as brownish spot and infected area shrinks as well as becomes hard.
  • The disease symptoms also appear on the underground tuber as rot.
  • Infected potato with rot exhibits two type of rot (i) Soft rot and (ii) Dry rot. Soft rot symptoms appear in the presence of excess of moisture and dry weather condition.
  • During the shortage of moisture on the skin of potato tuber bluish black or brownish irregular spot appears.
  • If infected potato is seen through cutting than water soaked or reddish brownish spots will be seen.
  • Cold storage potato may also be affected with soft rot.
  • Foul odour comes from potato field infected by late blight disease of potato caused by phytophtora species.

Disease Cycle:-

  • In plains during the summer atmospheric temperature is too high so that pathogen cannot survive in any stage.
  • In hills area the pathogen survive as soil borne as well as seed borne.
  • In cold storage hidden mycelium inside the tuber of potato serves as primary source of inoculum for the plains of north India.

Favorable environmental or climatic condition for the appearance of disease.

Favorable environmental and climatic conditions for the spread of disease are 100% relative humidity and temperature range of 15oc to 22oc. The development of pathogen stops at the temperature above than 30o c and pathogen becomes again active under suitable climate conditions.

Management aspects of the disease.

  • Always show health, disease free and certified seed in the field.
  • Destroy and dispose off residual matter properly after the harvest of the potato crop.
  • If infected crop with disease in the field should be harvested after the maturity of the crop.
  • Bunts in the field of the potato crop should be raised upto 15 to 20 c.m. to reduce the chances of contamination and infection.
  • Before the sowing the seed of potato tuber in the field, it should be treated with mercuriefungieide like Aretan 0.2% solution for 1 minute.
  • If, there is chances of disease appearance or disease has already been appeared on standing crop then spray the 0.2% solution of Dithane M-45/ or any suitable fungicide.
  • Select resistant variety of potato for sowing for different areas like KufariAlankar, KulfariNavtal and KufariBadsaha which are suitable for north-east area and KufariJeevan, KufariJyoti are suitable for Shimla and near by hilly areas.
  • Solution of mancozeb (Dithane – M45) or zineb (Dithane z-70) at the rate of 2.0-2.5 kg/100 litre of water per hectare or other suitable fungieides like Fytolan and Biltox-50.

By:-Dr. A.K Sharma
Department of Agriculture
Uttaranchal (P.G.) College Of Bio-Medical Sciences & Hospital