Tomatoes: stem problems

Although easy to grow and very rewarding, tomatoes can suffer from a range of problems with their stems, from the lumps and bumps of root initials to more serious stem rots caused by a variety of diseases.

Verticillium wilt on tomato. Credit: RHS/Pathology.

Quick facts

Plants affected Tomatoes
Main causes Humid conditions
Timing Summer

What is the problem?

Tomato stems occasionally show rots and distortions due to adverse growing conditions and/or diseases.

Symptoms and causes

  • Lumps and outgrowths on the stem, usually near the bottom: These are likely to be root initials, which often cause alarm to gardeners, but are in fact harmless. Tomatoes produce roots from their stem very easily, and this is usually no cause for concern.
  • Dead, rotten patches on the stems: A disease called Didymella can attack the stems of tomatoes causing dead rotted patches. Affected plants can wilt and die, and should be removed immediately to prevent infection of the remaining plants.
  • Brown streaks on the stems: Tomato blight and Fusarium wilt can cause brown streaks and rotten patches on the stems and leaves, usually accompanied by wilting. See the links below for further detail.
  • Wilting with staining inside the stem: This may be caused by the disease Verticillium wilt. See the links below for further detail.
  • Fluffy grey or white mould on the stems: This may be caused by Sclerotinia or grey mould (Botrytis cinerea). See the links below for further detail.

Links

Potato and tomato blight
Verticillium wilt
Sclerotinia disease
Grey mould

Biology

Root initials on the stems are encouraged by humid conditions. Root formation on the stems also seems more common when plants are under stress. Hormone weedkiller contamination promotes stem root formation, but the additional effects of this contamination on the foliage are more dramatic and are usually noticed first.

For details of the biology of tomato stem diseases, please see the specific pages on these diseases.

Links

Potato and tomato blight
Verticillium wilt
Sclerotinia disease
Grey mould
Weedkiller damage

Control

Root initials are not very significant, but they might indicate that fine-tuning of cultivation, especially watering methods might be needed. Keeping the stems and foliage dry when watering should remedy the problem, and will also help to prevent tomato blight.

Diseases that affect the stem usually persist in the soil. Changing to a system of growing in grow-bags or in pots will prevent these diseases. There are no soil fungicides or soil sterilisers available to home gardeners. Removal and destruction of all infected material is also a wise precaution.

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