Gray Mold

Gray mold is what appears overnight on your strawberries. 
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Where did it come from? And how did it happen so fast? Strawberries can go from nearly perfect to practically inedible in the blink of an eye. And it is called gray mold.

Gray mold on strawberry (Rasbak) CC BY-SA 3.0

Also known as botrytis fruit rot and botrytis bunch rot, gray mold is a fungal disease caused by Botrytis cinerea. It attacks bulbs, flowers, grapes, kiwifruit, pomegranates, rhubarb, tomatoes, and more.

The culprit

Botrytis cinerea is everywhere. It comes in the garden on wind, clothing, shoes, tools, and pets. It is in the air we breathe. Unless you live in a bubble, your plants and food are already in contact with gray mold. Luckily, this particular garden problem spends most of its time as a dormant, asexual spore that is relatively indestructible. Add a little spring rain or overhead watering, and things start to happen.

Gray mold on Riesling grapes (Tom Maack) CC BY-SA 3.0

Preventing infection

Most commercial grape growers apply fungicides to prevent infection by this ubiquitous fungus. As with downy mildews, black spot, and powdery mildew,, moisture control is the key. If leaves and fruit stay wet, they are more likely to become infected. [Remember those strawberries you washed before putting them in the fridge last night? Next time, wash them just before eating.]

Controlling gray mold

Once a gray mold infection begins, use potassium bicarbonate-based fungicides to reduce the spread of the disease. Remove dead and diseased plant tissue carefully because each bit can contain millions of fungal spores.

Some people are allergic to gray mold. It can also cause a rare lung disease known as winegrower’s lung.