Disease
Grey mould
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Watch for | Watch for in March | Watch for in April | Watch for in May | Watch for in June | Watch for in July | Watch for in August | Watch for in September | Watch for in October | Watch for in November |
What it is
Grey mould is one of the most widespread plant diseases there is, able to infect hundreds of different plants. It is a particular nuisance on strawberries and raspberries, on greenhouse tomatoes and lettuce, and on flowers in damp autumns. It usually takes hold where tissue is already weak, bruised or fading, then moves into healthy growth.
Symptoms
The classic sign is a fluffy, grey-brown mould that releases a puff of dust when disturbed. Before that, you may see soft brown patches on petals, leaves or fruit, or a brown, rotting band around a stem that causes everything above it to wilt. Strawberries rot on the plant, tomato fruit can show small pale rings known as ghost spots, and seedlings may collapse. Peonies suffer from a related botrytis that blackens buds and stem bases.
Cause
The fungus is almost always present in gardens, surviving on dead plant material and as small black resting bodies in the soil. It needs high humidity and cool to mild temperatures, so it flourishes in poorly ventilated greenhouses, in dense crops, and during wet spells in spring and autumn. Wounds, frost damage and old flowers left on plants give it an easy way in.
Control
Cut out and bin anything showing mould, cutting back into clean growth, and clear away fallen leaves, petals and dropped fruit. Open greenhouse vents and doors on all but the coldest days, and space or thin plants so air moves between them. Pick soft fruit as soon as it ripens and remove any rotting berries during picking. Fungicides are seldom needed in gardens; regard them as a last resort and follow the label.
Prevention
Water in the morning so leaves dry before nightfall, and water the compost rather than the foliage. Avoid injuring stems when tying in, remove faded flowers regularly, and do not overfeed with nitrogen. Tuck straw under strawberries to keep fruit off damp soil, and keep the greenhouse clean over winter.
Plants often affected
Could it be something else?
These problems share some of the same symptoms. Compare them, or run the symptom checker with these signs ticked.
Months to keep an eye out: March, April, May, June, July, August, September, October and November.
Sources
Identification and life-cycle details were checked against the references below. Text and advice are our own. See our editorial policy.