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Pith necrosis of tomato

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 lesion 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

  • Favored by high humidity, low light and large temperature difference between day and night
  • Favored by 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

Resistant varieties

There are no tomato varieties resistant to pith necrosis.

Cultural control

  • Use a balanced fertility program based on a soil test. Avoid use of excessive nitrogen
  • Reduce humidity through use of vents, proper plant spacing, staking and pruning of plants. This is especially important on cloudy days
  • Do not work in plants when foliage is wet
  • Promptly bag and remove infected plants, including roots to prevent spread
  • Use a commercial sanitizer to regularly clean pruning tools
  • Sterilize stakes, ties, trellises etc. with 10% household bleach or commercial sanitizer

Chemical control

There are no pesticides effective in managing pith necrosis.

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

Reviewed in 2016

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