Alternaria leaf spot

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Causal organism: Alternaria spp.

 

Alternaria leaf spot with its characteristic yellow halo around lesion (C. Lopes, Embrapa, Brazil).

 

Light brown lesions with dark brown concentric rings (G. Lawrence).

Diagnostic summary

 

  • What you see on plants

 - brown necrotic lesions on leaves, with typical bullís eye appearance  of concentric rings and well defined margins.

 

-  several lesions can fuse and cover a great area of the leaf followed by leaf drop.

  - usually spots are surrounded by a chlorotic halo.

 

- damage caused is mostly present in older leaves.

  • Lesions on leaves and chlorotic halo surrounding lesions are very similar to lesions produced by A. bataticola  on Alternaria stem blight but the latter is a more serious disease infecting the whole plant during the whole crop cycle.

  • Disease is spread by rain splash, irrigation water, wind and insects.

  •  Higher incidence when dry and rainy periods alternate during cropping. 

  • Occurs in all agroecological zones.

Taxonomy

Economic importance

Geographical distribution

Symptoms

Morphology

Biology and ecology

Host range

Diagnosis

Management

References

Alternaria stem blight

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