Tomato Bacterial Cankers

bacterial canker tomatoes

Bacterial canker is one of several bacterial diseases that can seriously affect tomato plants grown in backyard gardens as well as in greenhouses. Once canker takes hold of a tomato plant, it can result in an all out epidemic that can affect young fruit on neighboring plants in the outdoor garden and all plants inside a greenhouse.

Causes and Symptoms

A particular bacterium called Cornebacterium michiganense causes canker on tomato plants. The bacteria are actually very erratic, but once it takes hold they are extremely destructive. The actual organism that causes this disease is in the seeds and can survive temporarily in the soil and in a greenhouse, but much longer in the debris of plants. Either way, it lives long enough to spread and affect future plantings.

All tomato plants are susceptible to bacterial canker, starting with seedlings all the way to plants that are already producing fruit. The symptoms are considered to be either superficial or systemic. Superficial symptoms normally appear first on the young green fruit in the form of small white spots with a dark brown center. Systemic symptoms usually show up early in the seeds or very young seedling plants. These symptoms include wilting, discoloration of the leaf veins, and lesions on the fruit and stems of the plant.

Treatments and Control

Tomato bacterial canker is one of the hardest diseases in tomatoes to get under control. This is partly due to the difficulty of detecting the disease because of the wide array of symptoms. Another reason is that the disease is so infectious and there are no chemicals that can effectively treat it. Some of the best tomato bacterial canker treatments are:

  • Disease free seed selection – When growing tomatoes with seeds, it is important to obtain seeds that are certified to be disease-free. Never use seed whose source may be known to have had a bacterial canker. It is not recommended that tomato growers save and use their own seed.

    If non-certified seed is used, they can be treated in different ways that include soaking them in .8% acetic acid or 5% hydrochloric acid. You can also use a hot water treatment.

  • Tomato crop rotation – Since the bacteria survive well in the debris of the plants, it is important to rotate your tomatoes with crops that are not infected with the canker bacteria. After three years of rotation, the disease should be under control.

  • Sterilization – When reusing greenhouses and garden seedbeds in which infected plants were grown, the soil must be sterilized in order to kill the bacteria. Steam sterilization is the preferred method.

Comments from Other Gardeners
  • Paul J. Pfarr says:

    I live in Hart County Kentucky. Due to the fact that tobacco has been raised here for over 200 years, it’s very difficult to grow tomatoes.

    This year, I have taken them out of my garden, and isolated them into 5-gal buckets and specially prepared soil. In the meantme, I’m rehabilitating next year’s tomato plot with plastic and sunlight.

    Growing disease resistant tomatoes in buckets, I feel gives me a much better chance to monitor and cope with the overwhelming diseases that are in Ky soils.

  • Nick says:

    I have grown tomatoes successfully in buckets for years! When I plant my transplants, I add a good 2-3 cups of black kow and Espoma Tomato Tone fertilizer to the bottom of the bucket. It’s also easier to water and not wet the leaves when tomatoes are in buckets. last year I had a cherry tomato in a bucket called “Olive” that grew all over a trellis on my deck. You are right. Disease and insects are much easier to control.

  • saucelover says:

    I agree. Because I have such limited space, there are times that if I want to grow more than just a handful of produce, my tomatoes and herbs all go in buckets and they always seem to do a little better that way. The only problem that I have with the buckets is space on or around my porch.

    Regarding the canker, how do you sterilize your soil so that you aren’t just reinfecting new plants if there’s no chemical treatment for it? How long does the ground need to lay fallow, and does it affect other plants, too?

  • Vernon says:

    Should we eat tomatoes that have bacterial canker spots…….

  • rick padgett says:

    Canker was brought into by tomato crop I suppose from bad seeds.All bought from dealers, none saved.Did not have last year.
    Signs; rim of leaf,very edge, begin to turn brown eventually will spread and kill leaf.Copper, Daconil,Neem, 5% clorox spray and removal of leaves no help.Foliar spray of Texas Tomato Food and Fish Iml., no help.
    Nothing stops this disease so I assume it is canker.
    I want to take ALL methods to destroy this disease.Will rotate crop next year but want to do everything to eliminate from infected area.To include any cover crop methods that may help.
    Advice please!!

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