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Bacterial leaf spot

Bacterial spot of tomato and pepper, and bacterial blights of beans and coriander, spread in splashing water and on hands. Leaves develop small dark spots, sometimes with a yellow halo; peppers drop leaves; fruit gets rough, raised spots.

Bacterial diseases
A pepper leaf with small, dark bacterial spots
A pepper leaf with small, dark bacterial spots

What it looks like

Small, dark and many.

  • Tiny spots that look greasy at first.
    Water-soaked spots Tiny spots that look greasy at first.
  • Spots turn brown-black; on tomatoes the centres fall out.
    Dark centres Spots turn brown-black; on tomatoes the centres fall out.
  • Some spots are ringed with yellow.
    Yellow halos Some spots are ringed with yellow.
  • Raised, rough, brown spots on fruit.
    Scabby fruit Raised, rough, brown spots on fruit.

How to confirm it

Hold to the light.

  1. Angular, greasy spots

    Spots limited by veins, water-soaked at the edge.

  2. Wet weather spread

    Worst after storms and overhead watering.

  3. No rings or fuzz

    Unlike early blight or mildews.

What to do

No cure; limit the spread.

  1. Remove affected leaves

    Pick off spotted leaves when plants are dry.

  2. Stop splashing

    Water at the base and mulch.

  3. Stay out when wet

    Handling wet plants spreads bacteria.

  4. Copper spray

    A labelled copper fungicide slows spread on peppers and tomatoes.

Prevent it next time

  • Buy clean seed and healthy transplants.
  • Rotate away from tomatoes and peppers for a year.
  • Remove debris after harvest.

What not to do

Do not save seed from infected plants.

In the growing guides

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

Sources

  1. Bacterial leaf spot on peppers, University of Maryland Extension
  2. Bacterial spot of tomato and pepper, University of Minnesota Extension