Gray mold (botrytis)

Botrytis cinerea

also called Grey mould, Botrytis blight, Ghost spot

Fuzzy gray mold on flowers, fruit, and soft growth in cool, damp, still air. Remove affected parts promptly, thin congested growth, and ventilate under cover.

Fungus Serious Airborne sporesSpread by contactRain splash Spreads to neighbors

What you'll see

A gray-brown velvety fuzz on dying petals, fruit or soft stems that puffs out a cloud of spores when touched.
Beneath the fuzz the tissue is soft and brown, and the rot spreads outward from a wound, a dead petal or a leaf scar.
Strawberries and grapes rot on the plant and hold their shape as a furry ball rather than dropping.
Pale rings or halos on tomato fruit — ghost spot — where a spore germinated but the fruit resisted it.
Small hard black bodies the size of a mouse dropping form in the dead stems over winter.

Why it happens

An opportunist fungus that lives everywhere on dead and dying plant material and moves into living tissue through a wound, a bruise, a faded flower or frost damage. Its spores are constantly in the air, so control is about denying it damp, dying tissue rather than trying to exclude it.

Cool, damp, still conditions — a closed greenhouse in autumn, a wet fortnight at flowering time, a crowded seedling tray, or fruit left on the plant past its best. Cold nights followed by warm damp mornings are the classic trigger under cover.

Treating it

Cut out affected flowers, fruit and stems the moment you see them, into a bag rather than shaking them about.
Deadhead promptly and clear fallen petals and leaves off the soil and off the greenhouse floor.
Ventilate under cover, even in cold weather, and use a fan to keep the air moving.
Thin congested growth and space plants so foliage dries between waterings.
Cut back affected stems to clean tissue in dry weather, and bin the black resting bodies with them.

Keeping it away

Water in the morning and at the base so nothing is wet overnight.
Avoid bruising fruit and stems, and prune cleanly without leaving snags.
Keep the greenhouse cool and airy rather than warm and shut, and heat gently rather than sealing it.
Do not feed heavily with nitrogen, which gives soft tissue that rots first.
Harvest soft fruit promptly and completely, leaving nothing over-ripe on the plant.

Who gets it

Strawberries, grapes, tomatoes, lettuce, peonies, cyclamen, snowdrops and any soft or cut flower under glass.

and 13 more in the catalog