Leaf Spot

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What is Leaf Spot?

A leaf spot is a limited, discoloured necrotic area on a leaf that is caused by fungal, bacterial or viral plant diseases, or sometimes due to nematodes infestation, insects, environmental factors and toxicity.

Causal organism: Isariopsis clavispora Berk. & M.A. Curtis, Cercospora spp,

Cladosporium spp Link

Symptoms –

Black leaf spot

  • The disease is characterized by sooty tuft-like circular to irregular black spots on the underside of the leaves. Later, it covers the entire lower surface giving a sooty appearance.
  • The leaves show yellowish and brownish discolouration on the upper surface and drop prematurely.

Cercospora leaf spot

  • The disease manifests itself in the form of circular to oval spots, measuring up to 4 mm in diameter, epiphyllous, yellow at first and turning brown surrounded by a dark brown margin.
  • The spots grow larger and become visible on both sides of the leaves. The infected leaves fall off. Cercospora leaf spot is also found on Chinese jujube, causing leaf yellowing.

Cladosporium leaf spot

  • The symptoms appear in the form of small, light brown to brown irregular spots on the lower surface of leaves.
  • The disease starts on leaves closest to the soil surface.

Mode of spread –

Black Leaf spot

  • The fungus survives in plant debris and soil, which are the primary sources of infection.
  • Secondary infection is initiated from spores present in the air.

Cercospora leaf spot

  • The fungus produces dark coloured stroma.
  • It survives in debris and soil, the primary sources of infection.
  • The spores are disseminated by wind.

Cladosporium leaf spot

  • It is also spread by spores present in the air.
  • The fungal spores survive in plant debris and soil, the primary sources of infection.

Management:

Cultural PracticesChemical Control
Remove the infected leaves during pruning and dispose them away from the orchard. Foliar spray of –Copper Oxychloride 50% WP @2 gm/litre.Mancozeb 75% WP @2 gm/litre.Chlorothalonil 75% WP @2 gm/litre.Propiconazole 13.9% + Difenconazole 13.9% EC @ 1ml/litre.

References: –

  • https://agritech.tnau.ac.in/crop_protection/crop_prot_crop%20diseases_fruits_ber.html
  • https://ppqs.gov.in/sites/default/files/ber.pdf