Bacterial Spot

Bacterial Spot on red tomatoThis disease produces small, dark irregular spots on tomato and pepper leaves; leaves eventually turn yellow and drop off. This defoliation weakens plants and exposes developing fruits to sunscald. Small, dark, wartlike raised spots with slightly sunken centers may appear on green fruits. Rot organisms are able to enter the fruit at these spots and cause decay. Bacterial spot symptoms are similar to, and often indistinguishable from, bacterial speck.

Very warm, wet weather encourages the development of the disease. The bacteria overwinter in plant residues. This disease is a problem mainly in the East and Midwest.

Prevention and Control

  • Purchase certified disease-free seeds.
  • Remove volunteer tomato and pepper plants, which may harbor the bacteria.
  • Use a three- to four-year crop rotation for susceptible crops.
  • Space plants well apart and support vines to ensure good air circulation.
  • Use drip irrigation or soaker hoses instead of overhead watering to keep foliage as dry as possible.
  • Keep the soil surface covered with mulch to prevent spores from splashing up from the soil surface.
  • Remove infected plant parts from the garden and destroy them or add them to a hot compost pile.

Last updated: 03/14/2024