Pith necrosis of tomato
The bacteria Pseudomonas corrugata, P. viridiflava, Pseudomonas spp., and Pectobacterium carotovorum.
Tomato, pepper, and numerous vegetable and ornamental crops.
Signs and symptoms
- Symptoms first appear when tomato fruit are at the green mature stage
- Leaves turn yellow, lower leaves wilt
- Dark brown to black lesion on the stem
- Many adventitious roots form along the stem
- 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
- 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
- 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
There are no tomato varieties resistant to pith necrosis.
- 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
There are no pesticides effective in managing pith necrosis.
Reviewed in 2016