Gray mold

Gray mold, caused by the fungus Botryotinia fuckeliana (anamorph Botrytis cinerea), is a destructive plant disease affecting a wide variety of horticultural and agricultural crops. It acts as a necrotrophic pathogen, colonizing plant tissues by secreting toxins and enzymes that degrade cell walls, resulting in tissue decay.

The fungus has a broad host range, infecting both greenhouse and field-grown plants. Notable susceptible species include peanuts, Persian cyclamens, fuchsias, Carpathian bellflowers, Browallia speciosa, Clerodendrum thomsoniae, Exacum affine, and Slipper Flower. Its presence can be devastating for commercial nurseries and home gardeners alike.

Symptoms initially manifest as small, water-soaked spots on leaves, petals, or fruits. These lesions expand rapidly, turning brown and eventually developing a distinct fuzzy, gray, powdery coating consisting of fungal conidia. Infected flowers often wither and drop prematurely, while stems may show cankers that girdle the plant and cause sudden collapse.

Environmental conditions are the primary drivers of disease development. High humidity levels, poor airflow, and temperatures between 15°C and 22°C create an ideal environment for spore germination and mycelial growth. The pathogen survives in dormant structures called sclerotia, which can persist in soil and debris for extended periods, acting as a recurring source of inoculum.

Management strategies focus on reducing humidity and removing sources of infection. Cultural practices are the first line of defense, supplemented by chemical interventions when necessary.

• Improve greenhouse air circulation.
• Sanitize tools and surfaces regularly.
• Remove and destroy infected plant parts immediately.
• Avoid overhead irrigation to keep foliage dry.