Gray Mold Disease

Gray Mold

Gray MoldProven strategies for identifying and treating gray mold disease.


Found on a wide range of plants (too many to mention), gray mold (Botrytis cinerea) is a fungal disease that travels quickly through gardens, especially during damp, cool to mild weather. It can be identified as grayish colored soft, mushy spots on leaves, stems, flowers and on produce. Spots may become covered with a coating of gray fungus spores, especially if humidity is high. Fruit or plants shrivel and rot and often develop black, stone-like sclerotia under rotted parts.

Gray mold is often found near the soil surface or in the densest areas of the plant canopy. It develops on wilted flowers first, then spreads quickly to other parts of the plant. The disease may also occur in storage, causing rotting of harvested fruits and vegetables.

Gray mold overwinters on plants, in or on the soil, and as sclerotia. Spores develop when conditions are optimal, and are moved by wind or splashing water onto blossoms or young leaves, where they germinate and enter the plant. Spores require cool temperatures (45-60 F.) and high humidity (93% and above) to germinate. Germinating spores rarely penetrate green, healthy tissue directly, but can enter through wounds on growing plants. Cuttings are particularly susceptible to infection.


• Prune or stake plants to improve air circulation between plants. Make sure to disinfect your pruning equipment (one part bleach to 4 parts water) after each cut.

• If growing indoors use a small clip-on fan to improve air flow.

• Keep the soil under plants clean and rake up any fallen debris.

• Add a good amount of organic compost or mulch under plants. Mulches will prevent the fungal spores from splashing back up onto the flowers and leaves.

• Water in the early morning hours, or use a soaker hose, to give the plants time to dry out during the day.

• Do not compost infected leaves or stems and thoroughly clean up garden areas in the fall to reduce over wintering sites for the fungal spores.

• Copper or sulfur based organic fungicides will help by protecting plants from infections. Apply these weekly, when spring weather is continuously cool and wet or if Botrytis has been a problem in the past.

• The biological fungicide Mycostop has shown suppression of the disease when applied directly to susceptible leaves, flowers and fruits.

Tip: Safely treat most fungal and bacterial diseases with SERENADE Garden. This broad spectrum bio-fungicide uses a patented strain of Bacillus subtilis that is registered for organic use. Best of all, SERENADE is completely non-toxic to honey bees and beneficial insects.

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Photo Credit: Daily Mail, U.K.