Why Are My Tomato Leaves Brown?

Identify tomato leaf diseases and environmental problems

Tomato Leaf Problem Quick ID

Target-shaped spots: Early blight (starts at bottom)
Small spots + yellow halos: Septoria leaf spot
Large black patches: Late blight (spreads rapidly)
Brown edges only: Water/nutrient stress

Common Causes & Treatments

Early Blight (Alternaria)

Brown spots with concentric rings, starting on lower/older leaves. Caused by fungal spores in soil splashing onto leaves. Treatment: Remove affected leaves, mulch heavily, water at soil level, apply copper fungicide. Space plants for airflow.

Septoria Leaf Spot

Many small brown spots with dark edges and tan centers, yellow halos. Starts on lower leaves after fruit set. Treatment: Remove affected leaves, improve air circulation, avoid overhead watering, apply fungicide. Rotate crops yearly.

Late Blight (Phytophthora)

Large, irregular brown-black patches that spread rapidly in cool, wet weather. White mold may appear on undersides. Treatment: Remove entire affected plants immediately. Apply copper fungicide to remaining plants. This disease killed the Irish potato crop - take it seriously.

Environmental Stress

Brown leaf edges without spots usually indicate inconsistent watering, heat stress, or fertilizer burn. Treatment: Water deeply and consistently, mulch to regulate soil moisture, avoid high-nitrogen fertilizers, provide afternoon shade in extreme heat.

Frequently Asked Questions

Why do my tomato leaves have brown spots with rings?
Concentric brown rings (target pattern) indicate early blight (Alternaria). It starts on lower leaves and works upward. Remove affected leaves, improve air circulation, mulch to prevent soil splash, and apply copper fungicide. Avoid wetting foliage when watering.
Why are my tomato leaves turning brown from the edges?
Brown leaf edges often indicate inconsistent watering, fertilizer burn, or potassium deficiency. Check watering consistency, flush soil if over-fertilized, and ensure balanced nutrition. In containers, this is commonly caused by the soil drying out too quickly.
What causes dark brown/black patches on tomato leaves?
Dark brown to black patches spreading rapidly may indicate late blight (Phytophthora), a serious disease favored by cool, wet weather. It can destroy plants in days. Remove affected plants immediately, don't compost them, and apply copper fungicide to nearby plants.
Will brown tomato leaves recover?
No, brown leaf tissue is dead and won't turn green again. However, removing affected leaves and treating the underlying cause allows the plant to produce healthy new growth. Focus on prevention and protecting remaining healthy foliage.
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