Violet root rot

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Causal organism: Helicobasidium mompa Tanaka (teleomorph), Rhizoctonia crocorum (Fr.) DC. (anamorph)


Other names: violet blight, murasaki-mompa


Rotten storage root due to violet root rot (Source: Hua and Zhou, 1984).

Diagnostic summary

  • What you see on plants

- foliage becomes chlorotic and the leaves at the base of the plant abscise prematurely.

- fibrous roots rot and are packed together by a purplish brown mycelial mat.

- storage roots rot and covered by bundles of packed mycelia that give a web-like appearance. Decay develops from the distal towards the proximal (close to the plant) ends.

  • Most conspicuous characteristic of infested soil is the presence of mycelial cushions and bundles on soil surface under the plant.  Initially white, they become pink to brown then violet with age.

  • Symptoms start developing towards the middle of the growing season.

  • Favourable conditions include temperature around 27C,  high moisture, poor drainage and acid soils.

  • Has only been reported from some countries in Asia.


Economic importance

Geographical distribution



Biology and ecology

Host range

Detection and inspection



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