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Pith necrosis of tomato

Quick facts

  • Symptoms first appear when tomato fruit are at the green mature stage. Severely infected stems may crack or collapse.
  • Bacteria survive in infected plant debris and soil.
  • Use different cultural control strategies to manage the spread of the disease.

Pathogen

The bacteria Pseudomonas corrugata, P. viridiflava, Pseudomonas spp., and Pectobacterium carotovorum.

Host range

Tomato, pepper, and numerous vegetable and ornamental crops.

Identification

Signs and symptoms

  • Symptoms first appear when tomato fruit are at the green mature stage.
  • Leaves turn yellow, lower leaves wilt.
    Row of tomato plants. One plant has yellow leaves and some small fruit.
    Yellowing of tomato plant due to pith necrosis
  • Dark brown to black lesions form on the stem.
  • Many adventitious roots form along the stem.
    Close up of green tomato stem.  Thick, short, green roots starting to grow at base.
    Adventitious roots often form on plants infected with pith necrosis
  • If the stem is cut lengthwise, dark discoloration can be seen in the pith. Discoloration is darkest at the base of the plant but does not extend into roots.
    Base of tomato stem, cut the length of the stem.  Outside of stem is green with adventitious roots, inside is hollow with dark brown discoloration. Discoloration is darkest at the base of the plant but does not extend into roots.
    Dark discoloration of the stem pith due to pith necrosis
  • The pith has pocket-like cavities.
  • Severely infected stems may crack or collapse.
  • Affected plants are scattered in a seemingly random pattern in the crop.

Environment

  • Favors high humidity, low light and the large temperature difference between day and night.
  • Favors high nitrogen and excess irrigation.

Biology and disease cycle

  • Bacteria survive in infected plant debris and soil.
  • May be brought in on infected seed or transplants.
  • Spread on workers' hands, pruning tools, and by splashing rain or irrigation.
  • Bacteria need a wound or natural opening to start an infection.

Management

 | 

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

Reviewed in 2016

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