bacterial spot on a tomato leaf

Bacterial spot on a tomato leaf
Clemson University - USDA Cooperative Extension Slide Series

Updated: May 12, 2021

Small pimples or scabs on tomatoes 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 overwinter 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.
bacterial speck lesions
Bacterial speck lesions on tomato leaf.
Photo: Gerald Holmes, Strawberry Center, Cal Poly San Luis Obispo, Bugwood.org

Management

Rogue out infected plants. Buy clean, disease-free seed from a reputable supplier. If the seed has not been chemically or heat-treated, soak the 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 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.