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Tomato Stem Canker - Diseases

Tomato Stem Canker - Diseases

Tomato Stem Canker - Diseases

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.

Sue Sanderson T&M horticulturalist

Written by: Sue Sanderson

Plants and gardens have always been a big part of my life. I can remember helping my Dad to prick out seedlings, even before I could see over the top of the potting bench. As an adult, I trained at Writtle College where I received my degree, BSc. (Hons) Horticulture. After working in a specialist plantsman's nursery, and later, as a consulting arboriculturalist, I joined Thompson & Morgan in 2008. Initially looking after the grounds and coordinating the plant trials, I now support the web team offering horticultural advice online.