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Bacterial canker of tomato

Quick facts

  • Bacterial canker is primarily important on tomato.
  • It can also infect pepper.
  • The bacteria that causes the disease may survive on weeds that are closely related to tomato.


Cluster of tomatos on the vine.  The fruit is infected with small (1/4 inch), creamy, white spots with tan or brown centers on fruit (bird eye spot)
Fruit infection of bacterial canker

The bacteria Clavibacter michiganensis subspecies michiganensis.


Signs and symptoms

Symptoms vary with age of plant, type of infection, environment and other factors. This disease can be difficult to diagnose based on symptoms alone. Confirm diagnosis by sending a plant sample to the UMN Plant Disease Clinic.

Tomato vine and fruit. Vine is split open and brown.
Stem canker from bacterial canker of tomato


  • Small, white, raised spots may form on leaves.
  • Seedling completely wilts and dies.


Tomato leaves on grey back ground, edges of leaf turn brown, with a yellow border
Leaf infection of bacterial canker
  • Yellow to tan patches form between veins.
  • Edges of leaf turn brown, with a yellow border.
  • Dark, sunken veins on leaves and petioles.
  • Wilt on lower leaves, often on one side only.
  • Entire plant may collapse and die.


  • Brown streaks can be seen in the vascular system when the stem is cut open.
  • Stem splits forming long, brown cankers.
  • Yellow sticky fluid may emerge from cut stem when squeezed.
Tomato stem split open, center is hollow and brown
Internal discoloration of stem from bacterial canker


  • Small (1/4 inch), creamy, white spots with tan or brown centers on fruit (bird eye spot).
  • Fruit surface may appear netted or marbled.


  • Warm temperatures (75 to 90°F).
  • High moisture or relative humidity.

Biology and disease cycle

  • Infected seed or transplants spread the bacterial canker pathogen long distances and introduce it to new areas.
  • The disease easily spreads between seedlings in a transplant production greenhouse through workers' hands, equipment, and pruning and clipping of transplants.
    • One infected seed can result in many infected transplants, through which the disease can become established in high tunnels or fields.
  • Transplants may be infected yet not initially show symptoms.
    • In the field, infected transplants often die and secondary spread is limited or of little economic impact.
    • In tunnels or greenhouses, the disease easily spreads between transplants and between older plants through practices like pruning and staking. This can result in severe symptoms and yield loss.
  • The pathogen survives up to three years on non-decomposed tomato plant debris and can survive for several months on stakes and equipment, thereby readily infecting tomatoes planted in the same tunnel the following season.



Michelle Grabowski, Extension educator and Angela Orshinsky, Extension plant pathologist

Reviewed in 2018

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