Moon Orchid with White Mold? Rare but Treatable
Phalaenopsis amabilis
White mold (Sclerotinia sclerotiorum) is a devastating fungal disease affecting over 400 plant species worldwide. The fungus produces black, seed-like structures (sclerotia) that can survive in soil for 5 or more years. The disease is favored by cool, moist weather (50-68°F/10-20°C), especially during flowering.
ð Symptoms
- âĒ Sudden wilting and yellowing of leaves
- âĒ Fluffy white mold growth on stems and leaves
- âĒ Water-soaked lesions expanding irregularly
- âĒ Soft, watery rot near soil level
- âĒ Black sclerotia (0.5-1cm) in white fungal mass
- âĒ Grayish-green appearance before wilting
- âĒ Infected stem sections become brittle and tan-colored
â Possible Causes
- â Fungus Sclerotinia sclerotiorum surviving in soil via sclerotia
- â Prolonged cool, moist conditions (50-68°F/10-20°C)
- â High humidity during flowering period
- â Poor air circulation from dense planting
- â Wind-borne spores from germinated sclerotia
- â Direct contact with contaminated soil
- â Fungus survival on plant debris for 5+ years
ð Treatment
Quick Fixes
Immediate removal
Remove and completely destroy all infected plants. Burn or bag and dispose in trash.
Apply fungicide
Apply systemic fungicide (SDHI or DMI) to neighboring healthy plants preventively.
Reduce moisture
Stop all overhead watering. Use drip only. Improve ventilation/drainage.
Isolate area
Create buffer zone by removing plants within 20-inch radius of infection.
Intensive monitoring
Inspect remaining plants 2x daily for 14 days.
Organic Treatment
Remove infected plants
Carefully remove entire plant without spreading sclerotia. Burn or bury deeply (24+ inches). Do not compost.
Apply biocontrol
Apply Coniothyrium minitans to soil per instructions. This fungus parasitizes Sclerotinia sclerotia.
Improve circulation
Thin adjacent plants to improve airflow. Space plants 12-18 inches apart.
Adjust irrigation
Switch to drip irrigation. Water early morning. Avoid wetting foliage.
Soil solarization
If possible, cover soil with clear plastic for 4-6 weeks in summer (kills sclerotia).
Monitoring
Inspect plants daily for 3 weeks. Remove any new infection immediately.
ðĄïļ Prevention
- â Plant with proper spacing to promote air circulation
- â Avoid excessive irrigation during and after flowering
- â Use drip irrigation instead of overhead sprinklers
- â Remove and destroy infected plants immediately
- â Implement crop rotation with 2-3 years of non-host crops (cereals, corn)
- â Water early in day so foliage dries before nightfall
- â Clean up all crop debris after harvest
- â Avoid planting susceptible species in areas with disease history
ðą Care Guide: Moon Orchid
ð§ How to Water
Water thoroughly when the potting medium is nearly dry, typically every 7-10 days. Use room temperature water and avoid letting the plant sit in standing water. Reduce watering in winter.
âïļ Lighting
Place in bright, indirect light - an east or west-facing window is ideal. Avoid direct sunlight which can burn the leaves. In winter, supplemental artificial light can encourage blooming.
ðŠī Ideal Soil
Use a well-draining orchid mix consisting of bark chips, perlite, and sphagnum moss. The pH should be slightly acidic (5.5-6.5). Never use regular potting soil as it retains too much moisture.