University of Maryland Extension

Bacterial Spot - Bacterial Speck - Vegetables

small bacterial leaf spot lesions on tomato leaf

Small, brown to black irregular raised spots appear on tomato fruits and peppers.

  • The symptoms of bacterial spot disease begin as small circular pimples on leaf undersides and as small water-soaked lesions on the upper leaf surface. The spots enlarge and appear like small scabs on the fruit.
  • Spots enlarge during warm, wet and humid weather and turn brown.
  • Leaves will drop with severe infections, resulting in sunscald.
  • The bacteria over-winter on crop residue and are seed-borne.
  • The disease is spread by splashing rain and working with wet, infected plants. Hot, dry weather will slow the spread of this disease.
  • This is one of the most common diseases of peppers in Maryland.

Management

Rogue out infected plants. Buy clean, disease-free seed from a reputable supplier. If seed has not been chemically or heat treated, soak seed for five minutes in one pint of water and add two ounces of bleach. Rinse seeds thoroughly with clean, cool water and dry thoroughly.

Select resistant cultivars. Jalapeno and serrano chiles peppers seem to be less susceptible to bacterial spot than other types.

Cover the soil around pepper plants with a mulch and don’t crowd plants together. Avoid overhead watering and working with plants when foliage is wet. Fertilize plants to support new growth. Spray with a labeled copper fungicide, when symptoms are first observed. Remove and dispose of all infected crop residues. Where bacterial spot is a perennial problem consider covering the soil with black plastic or landscape fabric.

bacterial spot on bottom of tomato

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