Grey Mould (Botrytis)
Disease · Commonly affects: tomatoes, strawberries, grapes, raspberries, lettuce, sweet peas, cyclamen, geraniums
Grey mould, also called botrytis, is a fungal disease that colonises soft, damaged or ageing plant tissue. It thrives in cool, damp, still conditions, making it common in UK greenhouses, polytunnels and crowded borders. It can quickly spoil ripening fruit, flowers and cut stems, particularly where ventilation is poor.
How to identify it
The clearest sign is a soft brown patch followed by a fuzzy grey or grey-brown coating made of spores. It often starts on bruised fruit, spent flowers, dead leaves or a damaged stem. Small lesions may begin at 2-5 mm but can spread across a whole strawberry or tomato. Under glass, watch for grey fluff on tomato leaf joints, stems or dead petals. Affected tissue becomes watery, brown and easily collapses.
Damage
Grey mould rots fruit, flowers and stems, making harvests unusable and ornamental displays short-lived. On tomatoes and strawberries it can spread from one damaged fruit to nearby healthy ones. Stem infections may weaken or kill shoots above the affected point. In crowded crops, airborne spores can cause repeated losses throughout a damp spell.
Prevention
Keep greenhouses, cold frames and polytunnels clean, ventilated and free from dead leaves and spent flowers. Space plants to let air circulate, prune tomatoes sensibly, and support fruit so it does not sit on wet soil. Water at the base early in the day and avoid splashing foliage. Harvest ripe fruit regularly and handle it gently. Remove damaged plant material quickly, and avoid overcrowding pots and seed trays.
How to manage it
Cut away infected fruit, leaves and stems as soon as they are found, using clean secateurs between plants. Remove fallen petals and overripe fruit, which provide easy entry points. Bin diseased material rather than composting it. Increase ventilation under cover and reduce condensation by watering in the morning. Where stems are affected, cut back into healthy-looking tissue if possible. Keep harvesting sound fruit frequently to reduce further spread.
Grey Mould (Botrytis): frequently asked questions
How do I identify grey mould (botrytis)?
The clearest sign is a soft brown patch followed by a fuzzy grey or grey-brown coating made of spores.
How do I prevent grey mould (botrytis)?
Keep greenhouses, cold frames and polytunnels clean, ventilated and free from dead leaves and spent flowers.
How do I get rid of grey mould (botrytis)?
Cut away infected fruit, leaves and stems as soon as they are found, using clean secateurs between plants.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.