Grey mould is a very common disease of both edible and ornamental plants, particularly those grown in greenhouses. Read on to find out more in this pest and disease guide to botrytis.

What is grey mould?

Botrytis or grey mould is a fungal disease that affects healthy plants as well as those under stress. It mainly tends to affect damaged plants and seedlings. It takes hold by entering through the wound and then spreading to other parts of the plant.

It’s is very often found on lettuce but can affect other vegetables and fruit such as courgettes, cucumber, tomatoes, grapes, strawberries, and raspberries. It can also infect ornamental plants such as pelargonium, chrysanthemum, and cyclamen.

Both seedlings and mature plants are susceptible, especially if they’re overcrowded and being grown in a humid greenhouse.

It can strike at any time of the year but is more prevalent during the summer months. Plants grown in stressed conditions, as in a greenhouse, or outside in humid conditions with poor air circulation are particularly susceptible.

The first signs of infection are parts of the plant turning brown and soft and then becoming covered in a grey-brown fluffy mould. Seedlings can suddenly collapse as the fungus spreads to their young stems. On older plants, buds and flowers may also shrivel up and die off.


How to control it

To prevent grey mould, try to avoid too much humidity building up around the plants. You can do this by keeping windows and doors open in a greenhouse. Also make sure plants being grown under cover or outside are not overcrowded.

It’s important to remove any dead plants or parts of plants promptly.

There are no fungicides approved for use against grey mould by home gardeners.


To keep growing the best lettuce, courgettes, cucumbers, and tomatoes, keep the plants well ventilated and control humidity. With this pest and disease guide to botrytis or grey mould, you’re one step closer to having tasty harvests to eat. If you need specialist advice, I recommend you get in touch with your local garden centre.

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