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Early blight

Early blight is a fungal leaf spot that starts on the oldest leaves and climbs the plant. Spots have concentric rings and a yellow halo; leaves yellow and drop. It weakens plants and exposes fruit to sun, but rarely kills them outright.

Fungal diseases
A tomato leaf with brown target-like early blight spots
A tomato leaf with brown target-like early blight spots

What it looks like

Look low on the plant.

  • Brown spots with rings like a target.
    Target spots Brown spots with rings like a target.
  • Yellow tissue around each spot.
    Yellow halos Yellow tissue around each spot.
  • Oldest leaves yellow and drop.
    Lower leaves first Oldest leaves yellow and drop.
  • Dark sunken patches on stems.
    Stem lesions Dark sunken patches on stems.

How to confirm it

Check the pattern and the rings.

  1. Concentric rings

    Rings in the spots are distinctive.

  2. Bottom up

    Starts on old leaves and moves upward.

  3. Slow spread

    Much slower than late blight.

What to do

Slow it and keep the plant cropping.

  1. Remove affected leaves

    Take off spotted lower leaves and bin them.

  2. Mulch

    Mulch to stop spores splashing up from the soil.

  3. Water at the base

    Keep leaves dry.

  4. Feed

    Well-fed plants resist better.

Prevent it next time

  • Rotate tomatoes and potatoes on a 3-year cycle.
  • Grow resistant varieties.
  • Clear all debris at the end of the season.
  • Stake and prune for airflow.

What not to do

Do not compost infected leaves.

In the growing guides

Where the guides mention it, with plant-specific advice.

Sources

  1. Early blight of tomatoes, University of Maryland Extension
  2. Tomato diseases and disorders in the home garden, Penn State Extension