Alternaria blight

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Causal organism: Alternaria bataticola Ikata ex W. Yamamoto


Synonyms: Alternariosis, Anthracnose


Alternaria blight on leaves, petioles and stems of sweetpotato (C. Lopes, Embrapa, Brazil).

Diagnostic summary

  • What you see on plants

- initially small, brown to black oval lesions with a typical bullsí eye appearance of concentric rings on leaves, stems and petioles.


- as disease progresses, lesions become necrotic, usually surrounded by a wide yellow halo.


- soon after, the whole leaf blade turns chlorotic and drops. Blackened veins are observed on the lower side or undersurface of the leaf.


- lesions on petioles and stems are initially grey then turn black and sunken as they enlarge.  Petioles and stems are girdled and the plant dies.


- lesions get a silvery tone during dry conditions.


 - bases and middle sections are more affected than the vine terminals. The ground under affected vines is often carpeted with blackened leaf debris.

  • Very important in Eastern and Central Africa and Brazil.

  • Spreads by wind, rain splash, and water.

  • Incidence increases with altitude.


Economic importance

Geographical distribution



Biology and ecology

Host range





Other Alternaria leaf spots


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