Grey Mould (Botrytis)
TreatableFungal disease · spreads to other plants · also called botrytis blight, ghost spot
Botrytis is the mould that turns a forgotten punnet of strawberries grey, and it behaves the same way in the garden. It is an opportunist: it needs dead or damaged tissue and still, humid air to get started, which is why it is largely a hygiene and ventilation problem rather than a spraying one.
What it looks like
A soft, dusty grey-brown fuzz that puffs into a cloud of spores when disturbed. It colonises dead or damaged tissue first — spent flowers, pruning wounds, bruised fruit — then moves into healthy tissue beside it.
How to confirm it
- Grey fuzzy growth that releases a visible puff of spores when touched.
- Starts on dead flowers, wounds or bruised tissue, not healthy leaves.
- Thrives in cool, damp, still air — greenhouses and crowded beds.
- Pale rings on green tomatoes, called ghost spot, are the same fungus failing to establish.
What to do
- 1Remove dead flowers, damaged leaves and infected material promptly, and take it out of the garden.
- 2Increase airflow — thin crowded growth, open the greenhouse, run a fan indoors.
- 3Reduce humidity and stop overhead watering.
What it gets confused with
One observation settles each of these.
Downy mildew is confined to the leaf underside beneath yellow angular patches. Botrytis colonises dead tissue anywhere and is fluffier.
Powdery mildew is dry white powder on healthy leaf surfaces; botrytis is grey-brown fuzz on damaged tissue.
Preventing it next time
- Deadhead regularly and clear plant debris.
- Space plants generously and prune for air movement.
- Handle fruit gently; every bruise is an entry point.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.