Brown spots on tomato plants: causes and fixes

The most common causes of brown spots on tomato plants are early blight (*Alternaria solani*), Septoria leaf spot (*Septoria lycopersici*), bacterial speck (*Pseudomonas syringae*), bacterial spot (*Xanthomonas vesicatoria*), and late blight (*Phytophthora infestans*). Early blig

By Thomas Joseph Published 2026-06-11 Updated 2026-06-13 Reviewed by Thomas Joseph 8 min read

Brown spots on tomato foliage are one of the most common mid-season distress signals, and they're tricky because several diseases look similar at first glance. The spot's shape, size, edge pattern, and where it appears on the plant are the diagnostic keys.

Quick diagnostic table

Spot description	Plant location	Most likely cause
Brown spots with concentric rings (target pattern), yellow halo	Lower leaves first	Early blight (Alternaria)
Small (1/4 in) circular spots, gray-white center, dark border	Lower leaves first	Septoria leaf spot
Very small dark brown-black spots, water-soaked at first	Any location, leaves and fruit	Bacterial speck
Dark brown to gray-green water-soaked patches, spreading rapidly	Any location	Late blight (Phytophthora)
Brown, sunken spot on blossom end of fruit	Fruit only	Blossom end rot (calcium disorder)
Large irregular brown patches, no distinct spots	Upper/lower leaves	Bacterial canker, magnesium deficiency
Brown streaks inside stem	Cut stem base	Fusarium/verticillium wilt

Reader questions

Questions from other readers about this guide. Ask your own — if it's a good question, the answer goes here for the next reader.

Can I eat tomatoes from a plant with early blight?

Yes. Per Penn State Extension, "early blight on leaves does not affect fruit safety." Tomatoes from blighted plants are edible. You may see some stem-end or calyx damage from the fungus, but this is cosmetic.

What's the most reliable way to prevent tomato diseases?

Per NC State Extension, "choosing resistant varieties, rotating crops, and applying preventive fungicides when conditions favor disease" is the most effective approach. No single strategy is sufficient — all three together provide the best protection.

Is copper fungicide safe for organic gardening?

Copper is approved for organic production per USDA National Organic Program standards. Per UC IPM, "copper-based products are allowed in certified organic production." However, copper accumulates in soil with repeated applications — per Penn State Extension, "copper should be used judiciously and rotated with other approved products to avoid soil accumulation."

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Brown spots on tomato plants: causes and fixes

Quick diagnostic table

Brown spots on tomato plants: causes and fixes

Quick diagnostic table

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