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Bacterial spot of tomato and pepper

Quick facts

  • Bacterial spot can be a devastating disease when the weather is warm and humid.
  • Four closely related bacteria cause bacterial spot: Xanthomonas vesicatoria, X. euvesicatoria, X. gardneri, and X. perforans.
  • The disease can affect all above-ground parts of tomato and pepper plants: stems, petioles, leaves, and fruits.
  • Fruit spots commonly result in unmarketable fruit.

How to tell bacterial spot apart from other issues

The lower leaf canopy of a tomato plant with brown spots on the leaves.
Brown spotting with yellow hallowing caused by bacterial spot in tomato
  • When it first appears on the leaves, bacterial spot is similar in appearance to many other tomatoes diseases
  • Tomato leaves have small (less than 1/8 inch), brown, circular spots surrounded by a yellow halo.
    • The center of the leaf spots often falls out resulting in small holes.
    • The leaf spots do not contain concentric rings, spots with concentric rings are likely caused by early blight.
  • Pepper leaves have small (less than 1/8 inch), brown, circular spots that do not have a yellow halo and centers do not fall out.
  • Small, brown, circular spots may also occur on stems and the fruit calyx.
  • Fruit spots are 1/4 inch, slightly raised, brown and scabby.
    • Tomato fruit often have a waxy white halo surrounding the fruit spot.
    • Pepper fruit spots often occur on the stem-end of the fruit.
  • Spots occur on green and red fruit but do not result in rot.
A green tomato fruit with circular brown scabs.
Circular brown scabs on tomato caused by bacterial spot
A pepper leaf with irregular brown spots and holes.
Bacterial spot symptoms on pepper
A green bell pepper with circular, tan scabs caused by bacterial spot.
Bacterial spot caused spots on bell pepper

Biology

  • Four closely related bacteria cause bacterial spot: Xanthomonas vesicatoria, X. euvesicatoria, X. gardneri, and X. perforans.
  • Different strains infect either tomato or pepper or both.
  • All strains prefer high temperatures (75°F to 86°F), high humidity, and frequent rainfall/overhead irrigation.
  • Bacteria survive on plant debris in the soil for one to two years, but will not survive once plant debris break down.
  • Introduction is primarily on infected seed or infected transplants. Even seedlings that do not show symptoms may be infected and will show symptoms later in the growing season.
  • Bacteria can spread from plant to plant by tools, growers’ hands, or through splashing rain or irrigation water.
  • Between rotations, the bacteria may survive on tomato or pepper volunteer plants.

Managing bacterial spot in home gardens

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Managing bacterial spot on farms

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Authors: Marissa Schuh, horticulture IPM Extension educator, Anna Johnson, Michelle Grabowski and Angela Orshinsky

Reviewed by Natalie Hoidal, Extension educator

Reviewed in 2021

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