Leaf and stem scab

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Causal organism: ElsinoŽ batatas (Saw.) Viťgas & Jensen (teleomorph) and Sphaceloma batatas Saw. (anamorph)

 

Cupped, distorted and upright leaves showing the confluent scabby lesions along veins and petioles (J. O'Sullivan).

 

Brown, raised corky lesions on leaf (E. T. Rasco).

Diagnostic summary

  • What you see on plants

- first evident symptoms are small  yellowish to reddish brown spots on the leaves. As the disease advances, spots become corky outgrowth. Lesions merge and the whole affected tissue develops a scabby appearance.

 

- leaf veins are mostly infected. Affected portions stop growing, so the leaves curl and become contorted or twisted.

 

- lesions on stems may be circular, elongate or flat, depressed or slightly raised and brownish. Sometimes the borders are distinctly water-soaked. The lesions become rough and scab-like and can also coalesce to form larger lesions.

 

- young shoots become contorted and twisted. Badly affected plant parts dry out and die.

  • Transmitted by infected cuttings, rain splash, mist and dew or sprinkle irrigation.

  • Most severe fungal disease of sweetpotato in South East Asia and the Pacific.

  • Similar symptoms on the leaves are also caused by the thrips Dendrothripoides innoxius.

Taxonomy

Economic Importance

Geographical distribution

Symptoms

Morphology

Biology and ecology

Host range

Management

References

 

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