Late blight in Potato: Symptoms, Cause and Management

Dr. Deepali Tewari Pandey, GBPUAT

 

 

• This disease is caused by a fungus called Phytopthora infestans.
• The disease may attack almost any time after the crop has put up fairly good foliage.
• Initially, the lower leaves are infected. They show water-soaked lesions, especially towards margins. The spots enlarge if proper humidity and temperature are available.
• In humid atmosphere, the growth of the fungus can be seen on lower side of these spots as whitish cottony growth. The spots turn black as the affected leaves start rotting.
• The tubers under the ground also decay before harvest. On tubers, greenish sunken areas may be seen.
• Cool humid atmosphere favours the disease and prevalence of such weather can be an indication of disease in a short time ahead.

Control Measures

• Use potato tubers for seed from disease-free areas to ensure that the pathogen is not carried through seed tuber.
• The infected plant material in the field should be properly destroyed.
• Grow resistant varieties like Kufri Navtal.
• Fungicidal sprays on the appearance of initial symptoms. Spraying should be done with Dithane M-45 or Dithane Z-78 (2.5 kg/I 000 litres of water per hectare). Spraying should be repeated at 10-12 days' interval.