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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Potato > Tuber skin discolored

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Potato > Tuber > Tuber skin discolored

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  • Common Scab 1
  • Common Scab 2

Common Scab
Streptomyces spp.

  • Round rough, brown spots on tuber surface
  • Spots may be slightly raised and rough or slightly sunken depending on cultivar
  • Disease only affects tubers
  • Disease is favored by alkaline and dry soils
  • More information on Common Scab...
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  • Black Scurf/Rhizoctonia Canker 1
  • Black Scurf/Rhizoctonia Canker 2
  • Black Scurf/Rhizoctonia Canker 3

Black Scurf/Rhizoctonia Canker
Rhizoctonia solani

  • Small hard black spots stick to the skin of the tuber like dirt that won't wash off
  • Delayed or no emergence, have few stems, and poor growth
  • Underground stems and roots have brown, sunken dry spots
  • Tuber production is low, tubers may be small and deformed
  • In severe cases, small green tubers form on the stem above ground
  • Stem has a white to gray flaky growth just above the soil line.
  • Most problematic in cool wet soils
  • More information on Black Scurf/Rhizoctonia Canker...
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  • Image: 1

Silver Scurf
Helminthosporium solani

  • Brown to gray leathery patches form on tubers
  • Tuber has a silvery, metallic sheen on the surface when wet
  • Only the tuber skin is affected
  • More noticeable on red-skinned varieties
  • More information on Silver Scurf...

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