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Frog Eye Leaf Spot: Cercospora nicotianae

Tabacco

Symptom

Symptom Small, pale to brown, round or irregular spots measuring 0.5 - 3 mm in diameter and cracked centers appears on the affected leaves of the plant. Affected leaves become dry and fall off. The disease may cause cankers on the stem. The infection spreads to the bolls and finally fall off. During frequent rains large necrotic areas appear which destroy much of the leaf. During hot dry weather, frog eye-spot may be only pinpoint in size. In flue-cured tobacco the same pathogen causing infection at the harvesting time when cured results in innumerable, small, uniform, dark-brown to black spots popularly known as 'Barnspots' which affect the market value of the leaf. Management The nurseries should be located away from barns and all the diseased debris removed promptly and destroyed. Avoiding excess nitrogen fertilization and picking over ripened leaves also helps in minimizing leaf spotting. Fungicidal sprays with Bordeaux mixture 0.4% (4g/lit), Zineb 0.2% (2 g/lit) or 0.1% (1g/lit) Benomyl as per the schedule suggested under damping-off has checked leaf spotting in the seedbeds. In the field, removal of sand leaves immediately after the transplants have established, and weekly application of 0.4% (4g/lit) Bordeaux mixture or 0.1% (1g/lit) Benomyl or Thiophanate methyl or 0.03% (0.3g/lit) 5-6 weeks after planting has given adequate control of frog-eye spot.
  • Small, pale to brown, round or irregular spots measuring 0.5 - 3 mm in diameter and cracked centers appears on the affected leaves of the plant.
  • Affected leaves become dry and fall off.
  • The disease may cause cankers on the stem.
  • The infection spreads to the bolls and finally fall off.
  • During frequent rains large necrotic areas appear which destroy much of the leaf. During hot dry weather, frog eye-spot may be only pinpoint in size.
  • In flue-cured tobacco the same pathogen causing infection at the harvesting time when cured results in innumerable, small, uniform, dark-brown to black spots popularly known as 'Barnspots' which affect the market value of the leaf.

Management

  • The nurseries should be located away from barns and all the diseased debris removed promptly and destroyed.
  • Avoiding excess nitrogen fertilization and picking over ripened leaves also helps in minimizing leaf spotting.
  • Fungicidal sprays with Bordeaux mixture 0.4% (4g/lit), Zineb 0.2% (2 g/lit) or 0.1% (1g/lit) Benomyl as per the schedule suggested under damping-off has checked leaf spotting in the seedbeds.
  • In the field, removal of sand leaves immediately after the transplants have established, and weekly application of 0.4% (4g/lit) Bordeaux mixture or 0.1% (1g/lit) Benomyl or Thiophanate methyl or 0.03% (0.3g/lit) 5-6 weeks after planting has given adequate control of frog-eye spot.