Gray Mold

Plant disease · Botrytis cinerea

Description

Gray mold, also called Botrytis blight, is a fungal disease caused most commonly by Botrytis cinerea. It affects many garden plants, including strawberries, tomatoes, ornamentals, and seedlings. The fungus grows readily on aging flowers, damaged tissue, and fallen plant debris, then spreads to healthy tissue when conditions favor infection. Cool to mild temperatures, high humidity, and long periods of leaf wetness encourage outbreaks, especially in crowded beds and poorly ventilated greenhouses. Infected tissue develops soft brown lesions that become covered with fuzzy gray growth as the fungus produces spores. Flowers may turn brown and collapse; fruit can soften and rot; stems may develop lesions that cause shoots to wilt. Spores travel on air currents and can be moved by splashing water or handling plants. The fungus can persist on plant debris and produce new spores when damp conditions return. Although symptoms are conspicuous, disease severity varies greatly with weather and plant care.

Symptoms

• Fuzzy gray mold
• Spots on leaves
• Wilting
• Soft or rotting stems
• Rotting fruit
• Flowers or buds dropping
• Seedlings collapse at soil level

How to Identify

Look for soft, water-soaked or brown areas on flowers, fruit, leaves, or stems, followed by a dusty, fuzzy gray coating. Infection often begins on spent petals, bruised fruit, or other dying tissue and spreads where that material touches healthy growth. Gently disturbing an infected area may release a puff of gray spores; avoid doing this indoors or near other plants. Powdery mildew usually forms a white, flour-like coating on living surfaces rather than gray fuzz on rotting tissue. White mold tends to produce thicker, white cottony growth. Because several diseases cause brown spots or fruit rot, the characteristic gray spores are the strongest visual clue.

Prevention

Space plants and prune where appropriate so air can move through the foliage. Water at soil level, preferably early in the day, and avoid wetting flowers and fruit. Ventilate greenhouses and reduce persistent humidity; do not leave plants crowded together. Remove spent blooms, fallen leaves, and rotting fruit promptly, since these provide places for the fungus to grow and produce spores. Handle ripe fruit carefully to prevent wounds, and harvest it before it becomes overripe. Keep fruit off damp soil with suitable supports or mulch. Avoid excessive nitrogen fertilizer, which can encourage dense, tender growth. Inspect plants regularly during cool, damp weather and clean tools after working with diseased material. Healthy planting stock and good drainage also help limit conditions that favor disease.

Treatment

Start by removing infected flowers, leaves, and fruit, along with visibly affected stems where pruning will not seriously damage the plant. Work when plants are dry, handle moldy material gently to avoid dispersing spores, and bag it for disposal rather than leaving it in the bed. Clean pruning tools between affected plants. Remove badly diseased seedlings or plants that cannot be salvaged. Improve airflow, reduce humidity, and keep foliage dry; these steps help prevent new infections but will not restore rotted tissue. Harvest sound fruit promptly and discard any that develops rot. If gray mold repeatedly threatens a valuable crop, consider a biological or conventional fungicide specifically labeled for gray mold on that plant. Such products work best preventively or at the earliest signs of disease. Follow the label, including harvest restrictions, and rotate fungicides with different modes of action when repeated applications are permitted, because Botrytis can develop resistance.

Plants Affected

Carnation, Chickpea, Freesia, Geranium, Gerbera Daisy, Gladiolus, Grapes, Hyacinth, Impatiens, Lavender, Lentil, Lily, Lisianthus, Onion, Orchid, Paeonia, Pansy, Peony, Petunia, Rubus, Snapdragon, Snowdrop, Statice, Strawberry, Tulip

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