Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Potato > Tuber skin discolored
Potato > Tuber > Tuber skin discolored
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Greening
- Potato exposed to light turns a pale green color
- Potato tastes bitter
- Excessively green potatoes are poisonous
- More information on Greening
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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
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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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
