What is White Mold?
White mold is a fungal disease caused by Sclerotinia sclerotiorum that affects a wide range of vegetables, ornamentals, and other garden plants. It is characterized by a white, cottony fungal growth on stems, leaves, and fruits. The disease often develops in cool, moist conditions and can cause plants to wilt, rot, and die if left unmanaged.
Commonly affected plants include beans, tomatoes, peppers, sunflowers, lettuce, and many other garden crops.
Life Cycle
The fungus survives the winter as hard, black structures called sclerotia in the soil, on plant debris, or on infected plant parts. In spring or during favorable conditions, the sclerotia germinate and produce fungal mycelium or spores that infect plant tissue.
White mold spreads through direct contact with infected debris, water splash, or contaminated tools. Cool temperatures (60–70°F) and high humidity favor rapid disease development. The sclerotia can persist in soil for several years, making crop rotation and sanitation important for long-term control.
Symptoms
Early Stage
- Small water-soaked spots on stems or leaves
- Wilted or drooping leaves near the infection site
- Soft, discolored tissue developing at the base of stems or on fruit
Middle Stage
- White, fluffy fungal growth covering stems, leaves, or fruit
- Lesions enlarging and plant tissues becoming mushy
- Wilting spreading to entire plants
Late Stage
- Severe plant collapse and death
- Black sclerotia forming within or on infected tissue
- Decay spreading to neighboring plants in dense plantings
How to Control Disease Progression
Once white mold is detected, immediate action can reduce spread and protect healthy plants.
- Remove and destroy infected plants and plant debris promptly.
- Prune crowded plant areas to improve air circulation and reduce humidity.
- Avoid overhead watering that keeps foliage wet for extended periods.
- Disinfect tools after pruning or handling infected plants.
Treatment Options
Organic Methods:
- Apply compost teas or biological fungicides containing Trichoderma species to suppress fungal growth.
- Remove soil around infected stems to reduce contact with sclerotia.
- Mulch carefully to prevent soil splash onto stems and leaves.
Chemical Options:
- Use fungicides labeled for white mold control, such as those containing boscalid or thiophanate-methyl.
- Apply according to the label during early disease development for best results.
Step-by-Step Treatment Procedure:
- Identify and remove infected plants or tissues immediately.
- Improve spacing and airflow around remaining plants.
- Apply appropriate organic or chemical fungicide following label instructions.
- Repeat applications as necessary, especially during wet, cool periods.
- Monitor closely and continue sanitation to prevent new infections.
Expected Timeline for Recovery: Visible improvement may occur within a week after removing infected tissue and applying control measures. Full plant recovery depends on the severity of the infection; heavily infected plants may not recover.
Prevention Strategies
- Plant disease-resistant or tolerant varieties when available.
- Practice crop rotation and avoid planting susceptible crops in the same soil consecutively.
- Maintain proper plant spacing to improve airflow and reduce humidity.
- Water at the base of plants, avoiding wetting leaves and stems.
- Remove plant debris from the garden at the end of the season to reduce sclerotia survival.
- Monitor for early signs of infection and act quickly to remove diseased tissue.
- Consider using organic mulches to reduce soil splash but keep them away from direct contact with stems.
