Why are my strawberries going mouldy before I can pick them?

Grey mould thrives on contact, damp and still air — so the fixes are all physical: get the fruit off the soil, get air through the plants, and never water over the top.

Difficulty: beginner
Time: 30 min
Read: 5 min

Short answer

Grey mould, botrytis. It infects at flowering and shows up on the ripening fruit, and it spreads by contact. Get straw or mats under the fruit, space plants for airflow, water at the base only, pick every day or two, and remove every mouldy berry from the bed rather than dropping it.

Botrytis is everywhere in a UK garden and is not something you can exclude. What you can change is whether conditions favour it: it needs moisture on the surface and still humid air, and it moves from one berry to the next by touch. That means a strawberry bed with fruit lying on wet soil in a crowded, unventilated block will rot, and the same variety on straw with air moving through it largely will not.

What you'll need

Barley straw or strawberry mats
Secateurs or scissors
A bag for infected fruit
Cloche or fleece for wet spells (optional)

Step by step

Confirm it is grey mould.A soft brown patch that becomes covered in a grey-brown fuzzy coating, spreading fast, especially where two berries touch. It is quite distinct from slug damage, which leaves ragged holes and a slime trail.
Get the fruit off the soil.Straw tucked under the trusses as the fruit forms, or proprietary strawberry mats, or growing in pots and baskets. This is the single most effective measure and it is what the straw in the name is for.
Space the plants properly.35–45cm apart. Crowded plants keep the air still and humid around the fruit, which is exactly what botrytis needs. Thin an overcrowded bed by taking out the oldest plants.
Water at the base, never over the plants.Overhead watering wets flowers and fruit and splashes spores about. A can with the rose off, at soil level, in the morning.
Remove old and yellowing leaves through the season.It opens the plant up and removes dying tissue, which is where botrytis establishes itself before moving to the fruit.
Pick every day or two once fruiting starts.Ripe fruit left on the plant is where infection takes hold, particularly in a wet spell. Frequent picking is a control measure in itself.
Remove every infected berry, and take it out of the garden.Do not drop it on the bed and do not put it on an open compost heap. Each mouldy fruit releases a huge number of spores.
Cover the bed in a wet spell if you can.A cloche or a fleece tunnel over the row during prolonged rain at fruiting keeps the fruit dry, which is worth more than anything sprayed.
Clear the bed after picking.Cut the old foliage back to about 10cm above the crowns, remove the straw and all the debris, and burn or bin it. This resets the disease load for next year.

Tips

Hanging baskets and tall pots keep fruit off the soil entirely and away from slugs, and are a genuinely practical answer in a wet garden rather than a decorative one.
Growing through a weed membrane or on black plastic keeps fruit clean and stops soil splashing onto it.
Botrytis on one berry infects the ones touching it within days. Picking daily in a warm wet spell is the difference between losing some and losing most.
The same mould causes the collapse of stored strawberries in the fridge — infection was already present at picking.
Fruit that has been in contact with mouldy fruit should not be kept; discard rather than trim.

Common mistakes

Leaving mouldy fruit on the plant or the ground — Each infected berry is a spore factory sitting in the middle of the crop. Remove them into a bag every time you pick.
Watering with a sprinkler or over the leaves — It wets the fruit and splashes spores. Water at the base, in the morning, so anything wet dries quickly.
Planting too close to get more fruit in — Crowding creates the still humid air the mould needs, and the extra plants lose more fruit than they add.
Composting infected fruit in a cool heap — Botrytis survives it comfortably. Bag it or use a hot heap.

If it doesn't work

Grey furry mould on ripening fruit

Cause: Botrytis, spreading by contact and favoured by damp still air — Fix: Straw under the fruit, thin for airflow, water at the base, pick daily and remove every infected berry from the garden.

Ragged holes and slime trails

Cause: Slugs and snails — Fix: Get the fruit off the soil, and use whichever slug control you prefer around the bed rather than treating it as a disease.

Fruit rotting at the point of contact with the soil

Cause: Direct soil contact and wet ground — Fix: Straw or mats under every truss, or grow in containers.

Small, hard, brown, dried fruit rather than soft rot

Cause: Poor pollination, drought or frost damage to the flowers — Fix: Different problem — check for frosted flower centres and improve watering.

Whole plant collapsing with rotting crown

Cause: Crown rot or vine weevil larvae — Fix: Lift and inspect the roots. Crown rot means removing the plant; grubs in the roots mean vine weevil.

Questions people ask

Why do my strawberries go mouldy so quickly?

Grey mould infects at flowering and develops on the ripening fruit. Fruit lying on damp soil in crowded, still air is the ideal condition for it, and it spreads by contact from berry to berry.

Does straw really help?

Yes, substantially. It keeps the fruit off wet soil, stops soil splashing onto it, and lets air circulate underneath. It is the traditional answer because it works.

Can I eat strawberries next to a mouldy one?

Discard both. Soft fruit lets mould spread beyond what is visible, so it is not safe to simply trim the mouldy part off.

Is there a spray for grey mould on strawberries?

Garden options are limited and the cultural measures do most of the work. Getting fruit off the soil, spacing for airflow and picking frequently are far more effective than anything you can spray.