Soil rot or pox

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Causal organism: Streptomyces ipomoeae (Person & Martin) Waksman & Henrici


Other names: pox, pit, ground rot, soft rot


Soil rot in the root system (C. Clark, APS).


Sunken lesions due to infection just before harvest (W. Martin, APS).


Misshapen root due to infection at early storage root formation (W. Martin, APS).

Diagnostic summary

  • What you see on plants

- fibrous roots  have dark lesions and are easy to break.


- plants become stunted, leaves are smaller and pale or bronzed and early flowering results.


- lesions may form on stems in contact with soil.  They are dark, dry and scaby, and occasionally the plant can be girdled.


- lesions on storage roots ("pox") are roundish, shallow, dry, dark spots, usually with a scaby or cracked surface.


- when infection occurs while the root is still growing, deformities occur as the lesion restricts expansion.  The root becomes indented or constricted at the lesion.


- roughening of the skin rather than discrete lesions can be observed in some genotypes.

  • Infection can begin at any time in the growing season.
  • Infected plants are seen as large patches in the field.

  • Has been reported only from Japan and USA.

  • Favoured by dry weather, warm temperatures, a light well-drained soil and soil pH above 5.2.


Economic importance

Geographical distribution



Biology and ecology

Host range

Inspection and diagnosis



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