Brown Spots on Swiss Chard — Cercospora Leaf Spot
Set your conditions — the recommendation updates instantly.
GardenSays
Best match: Cercospora leaf spot. Manageable if you act.
- Best match
- Cercospora leaf spot
- Severity
- Minor
- Causes checked
- 1
Based on brown/gray spots with a purple border on the lower leaves with moist soil, the closest match is cercospora leaf spot. Confirm it against the actual plant: Circular brown-to-gray spots about 1/8-3/16 inch across with a distinct reddish-purple border; older lower leaves hit first, worst in warm humid weather.
- 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: Circular brown-to-gray spots about 1/8-3/16 inch across with a distinct reddish-purple border; older lower leaves hit first, worst in warm humid weather.
- 2.Pick off and destroy spotted leaves, space plants for airflow, and water at the base, not the leaves. Rotate away from beets/chard next year. The plant usually keeps producing clean new leaves.
- 3.Collapsing fast (days, not weeks)? Photograph it and check with your county extension before treating
Calculated result · 2 verified sources · Checked 2026-07-18 · How we decide
Why
What to do: Pick off and destroy spotted leaves, space plants for airflow, and water at the base, not the leaves. Rotate away from beets/chard next year. The plant usually keeps producing clean new leaves.
- 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
Swiss chard: brown/gray spots with a purple border — 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. Cercospora leaf spotmatch score 1Calculated result
Distinguishing signs: Circular brown-to-gray spots about 1/8-3/16 inch across with a distinct reddish-purple border; older lower leaves hit first, worst in warm humid weather.
Data sources
- Cornell University — Cercospora leaf spot on beets and Swiss chard — Cercospora leaf spot (Cercospora beticola) develops in warm, humid weather: circular brown-to-gray spots about 1/8-3/16 inch with distinct reddish-purple borders, lower/older leaves infected first and most severely; especially destructive on chard and beet greens. (checked 2026-07-18)
- University of Minnesota Extension — Spinach leafminer — Leafminer larvae tunnel inside the leaf, creating winding pale mines that widen into irregular brown blotches; the same pest attacks spinach, beets and Swiss chard. (checked 2026-07-18)
What changes this answer
Where on the plant?
Soil right now
Every change updates the answer, the math, the weekly steps and the share link instantly.
More plant problems tools: see all →