Rough, Scabby Patches on Potato Skin
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GardenSays
Best match: Potato scab. Manageable if you act.
- Best match
- Potato scab
- Severity
- Minor
- Causes checked
- 1
Based on rough or scabby patches on the tubers on the lower leaves with moist soil, the closest match is potato scab. Confirm it against the actual plant: Dark, rough, corky raised or pitted patches on the skin of the tuber. The flesh underneath is unaffected.
- This is a symptom-pattern match from your written description, not a lab diagnosis. If the plant is collapsing over days (not weeks), treat it as the worst plausible cause until ruled out.
Do this this week
- 1.Confirm it first: Dark, rough, corky raised or pitted patches on the skin of the tuber. The flesh underneath is unaffected.
- 2.Peel and eat as normal — scab doesn't rot the tuber. Keep soil consistently moist during tuber formation and avoid high soil pH to reduce it next season.
- 3.Collapsing fast (days, not weeks)? Photograph it and check with your county extension before treating
Calculated result · 3 verified sources · Checked 2026-07-17 · How we decide
Why
What to do: Peel and eat as normal — scab doesn't rot the tuber. Keep soil consistently moist during tuber formation and avoid high soil pH to reduce it next season.
- A symptom tree ranks causes by how well your conditions match each cause's known pattern — the distinguishing signs are how you confirm it on the actual plant, not a lab result.
- Most leaf problems trace to water, weather, or common leaf-spot fungi; true plant-killers are rarer but worth ruling out first.
When this doesn't apply
- If the plant is collapsing fast (days, not weeks), treat it as the most severe possibility on the list until proven otherwise.
- Multiple symptoms at once usually means the top cause here plus plain stress — fix watering first, then re-check.
How this was calculated
- 1. SymptomSource guidance
Potato: rough or scabby patches on the tubers — 1 known cause evaluated (extension-sourced)
- 2. Your conditionsCalculated result
Location on plant: lower; soil: moist. Causes whose known pattern matches these conditions rank higher — this narrows the list, it doesn't identify anything.
- 3. 1. Potato scabmatch score 1Calculated result
Distinguishing signs: Dark, rough, corky raised or pitted patches on the skin of the tuber. The flesh underneath is unaffected.
Data sources
- University of Minnesota Extension — Early blight in tomato and potato — Small dark spots form on older foliage near the ground; leaf spots are round, brown, up to 1/2 inch, with target-like concentric rings on larger spots. One of the most common potato diseases. (checked 2026-07-17)
- University of Minnesota Extension — Late blight of tomato and potato — Potentially devastating; infects leaves, stems and tubers. Leaf infections are large brown blotches with a green-gray edge. Favors cool (60-70F), damp conditions and can cause total crop failure if untreated. (checked 2026-07-17)
- University of Minnesota Extension — What's wrong with my plant? (potato tuber diagnostic) — Potato scab is a bacterial disease causing dark, rough, corky spots on the skin of the tuber but does not rot them — ugly but completely edible. (checked 2026-07-17)
What changes this answer
Where on the plant?
Soil right now
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People also ask
Is this early or late blight instead?
Can't reliably tell Early blight (Alternaria) and Late blight (Phytophthora) apart from what you've described — they need different responses, so check the signs below before treating. Calculate yours →