Botrytis gray mold is the fuzzy grey mould that ruins strawberries, rots lettuce hearts, blights rose buds, and turns a greenhouse bench into a grey, dusty mess. It is easy to recognise: a soft, grey, fuzzy growth that covers the affected part, often with a halo of water-soaked tissue around it, and a cloud of spores that puffs into the air if you disturb it. The fruit or flower underneath collapses into a soft rot, and the mould spreads to whatever it touches. A strawberry that was perfect yesterday can be half grey today, and a whole punnet can follow in a day.

The fungus is Botrytis cinerea, and it is one of the most common plant diseases in the world, because it attacks an enormous range of plants and thrives in the cool, damp, still conditions that are common in spring and autumn, in greenhouses, and in crowded beds. It is an opportunist: it enters through wounds and through dead or dying tissue — a fading flower petal, a damaged leaf, a fruit touching wet soil — and from there it invades healthy tissue. It does not need a wound on soft fruit, where it can enter directly. The good news is that botrytis is very sensitive to dry air and sunlight, and the same habits that control most leaf diseases — airflow, spacing, dry foliage, and removing dead material — control it very effectively.

What botrytis gray mold looks like: symptoms

  • Fuzzy grey mould: a soft, grey, fuzzy growth on fruit, flowers, leaves, or stems, often starting on a dead petal or a damaged spot and spreading outward.
  • Soft, water-soaked rot: the tissue under the mould turns soft, brown, and water-soaked, and it collapses easily when touched.
  • Rotting fruit: strawberries, raspberries, and grapes develop grey mould that starts at one point and covers the whole fruit in a day or two, often spreading to the fruit touching it.
  • Blighted flowers: buds fail to open, or open brown and mouldy, and the mould spreads from the flower into the stem.
  • Leaf spots and blight: grey-brown spots on leaves that enlarge and may be covered in mould in damp weather, often starting at the leaf edge or on a damaged area.
  • Stem cankers: on tomatoes and other plants, the mould can form a grey canker on the stem that girdles it and kills the growth beyond.
  • A cloud of spores: disturbing a mouldy plant releases a visible puff of grey dust — the spores — which is a sign to handle the plant gently and dispose of it carefully.

Botrytis moves fast in the right conditions. A strawberry can go from a small grey spot to a fully mouldy fruit in 24 to 48 hours in cool, damp weather, and the mould then spreads to every fruit it touches. On lettuce and other leafy plants, it starts in the older, lower leaves or in the heart and spreads outward over days. On roses and peonies it blights buds in spring, then eases as the weather warms and dries. The disease is worst in spring and autumn, when temperatures are cool and the air is damp, and in greenhouses, where it can persist all year. In hot, dry, sunny weather it almost disappears, and new growth comes through clean.

Which plants get botrytis gray mold

Botrytis attacks almost anything soft and fleshy: strawberries, raspberries, grapes, lettuce, tomatoes, peppers, eggplants, cucumbers, beans, peas, onions, and many flowers including roses, peonies, dahlias, geraniums, and cyclamen. It is a major problem on soft fruit, where a single infected berry can rot a whole cluster, and in greenhouses, where the still, humid air suits it perfectly. It also attacks houseplants kept too wet, and it rots stored bulbs and cut flowers. Few plants are completely immune, which is why the disease is a matter of conditions and hygiene rather than of variety alone.

Conditions that favour botrytis gray mold

Botrytis needs cool, damp, still air: temperatures in the 60s and low 70s Fahrenheit with high humidity and leaves wet for many hours. It is worst in spring and autumn, in greenhouses, in crowded beds, and in shade. It enters through wounds and dead tissue, so damaged leaves, fading flowers, and fruit touching wet soil are the usual starting points. The fungus overwinters in plant debris and in the soil, and it produces enormous numbers of spores that travel on the wind and in water. Plants that are overfed with nitrogen and full of soft, lush growth are more vulnerable, and any plant that is stressed or damaged is an easier target.

How botrytis gray mold spreads

Botrytis spreads by spores that travel on the wind, in splashing water, and on hands, tools, and clothing. A single mouldy strawberry can release enough spores to infect the whole bed, and the spores can travel a long way on a breeze, which is why the disease can appear suddenly across a neighbourhood after a wet spell. It also spreads by direct contact — a mouldy fruit touching a healthy one infects it — and in infected debris left in the garden. The fungus survives the winter in dead plant material and in the soil, so the previous year's debris is the usual source of the next year's outbreak.

How to tell it apart from lookalikes

Botrytis is sometimes confused with other moulds, but its grey, fuzzy growth on soft, rotting tissue is distinctive. Powdery mildew is a white powder on the leaf surface, not a grey mould on rotting fruit. Downy mildew makes a greyish growth on leaf undersides but does not rot fruit the way botrytis does. Brown rot on stone fruit makes brown, firm rot with tan spore tufts rather than a grey fuzzy mould. Bacterial soft rot makes a wet, slimy, foul-smelling rot without the fuzzy grey growth. If the rot is soft, grey, and fuzzy, and it spreads to whatever it touches, botrytis is the most likely answer.

Prevention: cultural steps that work

  • Space plants generously and prune for airflow so leaves and fruit dry quickly after rain or watering.
  • Water at soil level, in the morning, and avoid wetting the foliage and the fruit.
  • Mulch under strawberries and other soft fruit so the fruit does not touch wet soil, and use straw or a similar mulch that keeps the fruit clean and dry.
  • Remove fading flowers, dead leaves, and damaged fruit promptly, since botrytis starts in dead tissue.
  • Pick fruit as soon as it ripens, and pick it in dry weather, handling it gently so it is not bruised.
  • Ventilate greenhouses well, and avoid overcrowding plants inside them.
  • Feed moderately and avoid heavy nitrogen that pushes soft, lush growth.
  • In autumn, clear all plant debris from the beds and the greenhouse, and do not compost diseased material.

Treatment step by step

  1. Remove every mouldy fruit, flower, and leaf as soon as you see it, handling it gently so the spores do not puff into the air, and dispose of it with household waste — do not compost it and do not leave it on the soil.
  2. Improve airflow by thinning crowded growth and spacing plants, and open greenhouse vents so the air moves and the humidity drops.
  3. Stop overhead watering and switch to watering at soil level, in the morning, so the foliage and fruit stay dry.
  4. Mulch under the plants to keep fruit off wet soil, and lift fruit that is touching the ground onto clean straw or a support.
  5. Pick the remaining fruit promptly, even if it is slightly underripe, since ripe fruit left on the plant is the most vulnerable.
  6. If you choose to spray, a fungicide labelled for botrytis on the plant in question can protect new growth, but it will not cure mould that is already there. Apply it to clean new foliage exactly as the label directs.
  7. At the end of the season, clear all debris from the bed and the greenhouse so the fungus does not overwinter there.

What recovery looks like

Recovery from botrytis is usually quick once the weather dries and the mouldy material is removed: new fruit comes through clean, new leaves stay healthy, and the plant resumes growing. The mouldy fruit and leaves will not recover and should be removed, but the plant itself is rarely badly damaged unless the mould has girdled a stem. Strawberries often recover within a week of dry weather, and the next picking can be clean even after a bad outbreak. The long-term recovery is about the following year: clean beds, good spacing, and mulch will keep botrytis to a few berries rather than a whole crop.

When a plant is beyond saving

A plant is beyond saving from botrytis when the mould has covered most of its fruit and foliage, when the stems are girdled, and when new growth keeps coming through mouldy despite dry weather and cleanup. Annuals in that state are best pulled out, since they will not produce a worthwhile crop. Perennials such as strawberries and roses are rarely beyond saving — a hard cleanup, a mulch, and a season of good culture will usually restore them, and the disease is a recurring nuisance rather than a killer unless it returns severely for several years running.

Frequently asked questions

Can I eat strawberries with botrytis gray mold?

No. Cut away the mouldy part is not enough on a soft fruit like a strawberry, because the mould spreads invisibly through the soft flesh. Discard any berry with grey mould, and do not eat berries that were touching a mouldy one unless they are completely clean.

Why does botrytis hit my strawberries every year?

The fungus overwinters in debris and in the soil, and it returns in the first cool, damp spell of spring. Thorough autumn cleanup, mulch to keep the fruit off the soil, spacing for airflow, and prompt picking are the ways to break the yearly cycle.

Does botrytis spread to other plants?

Yes, very easily — its spores travel on the wind and it attacks a huge range of plants. A mouldy strawberry can infect the lettuce next to it, so removing mouldy material promptly protects the whole garden.

Can I compost mouldy strawberries?

No. Home compost rarely gets hot enough to kill botrytis spores, so composting mouldy fruit returns the disease to the garden. Bag the fruit and put it with household waste.

Is gray mold the same as powdery mildew?

No. Gray mold is a soft, grey, fuzzy mould on rotting tissue, while powdery mildew is a white powdery coating on the leaf surface. They need different conditions and different controls, though both are helped by airflow and dry foliage.

Getting help and going further

If you are unsure which disease you are dealing with, take clear photos of the symptoms and check your local extension service — they can confirm a diagnosis from a sample and advise on the varieties and the timing that work best in your area. You can also try our plant disease checker to narrow down the problem, and browse the guides hub for related disease guides. For growing advice, see growing strawberries. For growing advice, see growing lettuce. For growing advice, see growing tomatoes. Related guides: brown rot fruit, sooty mold, powdery mildew on squash. Whenever you remove diseased material, dispose of it with household waste — do not compost diseased material, since home compost rarely gets hot enough to kill the organisms that cause these diseases. Good record-keeping helps too: note the date, the weather, and the variety when a problem first appears, so you can spot the pattern next year and act earlier.