Thompson & Morgan

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Tomato Stem Canker - Diseases

Commonly asked question(s):

- Why are tomato branches black and mouldy?

Why are tomato branches black and mouldy?

It sounds as though they may be suffering from a fungal disease. If it is just the stems (and not the leaves) that are going mouldy then the cause may be a stem canker. This tends to be the result of fungal spores entering a wound in the stem (possibly where the side shoots removed).

Fungal problems tend to be exacerbated by humid conditions. From your photo it looks like they are in a greenhouse. A good preventative measure would be to increase the ventilation by leaving the door and windows open and watering in the evening rather than the morning to reduce humidity.

End of season plant sale