Golden Shower Orchid with Gray Mold (Botrytis Blight): Prevention & Cure
Oncidium varicosum
Gray mold, caused by the fungus Botrytis cinerea, is one of the most common fungal diseases in plants. It affects over 200 plant species, including ornamentals, vegetables, fruits, and houseplants. The disease thrives in cool, humid conditions with poor air circulation, causing grayish spots and soft rot on infected tissues.
ð Symptoms
- âĒ Grayish colored soft, mushy spots on leaves, stems, and flowers
- âĒ Gray fuzzy coating of fungal spores, especially in high humidity
- âĒ Brown to gray circular spots on leaves and petals
- âĒ Shriveled and rotted fruit or plant parts
- âĒ Black, stone-like sclerotia under rotted parts
- âĒ Water-soaked lesions that expand rapidly
- âĒ Wilting and collapse of affected tissues
â Possible Causes
- â High humidity (above 85%) combined with moderate temperatures (64-73°F/18-23°C)
- â Poor air circulation around plants
- â Overwatering or standing water on foliage
- â Dense plantings with inadequate spacing
- â Damaged or stressed plant tissues
- â Dead flowers and leaves not removed
- â Low light conditions
ð Treatment
Quick Fixes
Remove and dispose of all visibly infected parts
Remove and dispose of all visibly infected parts
Isolate plant from other healthy plants
Isolate plant from other healthy plants
Apply chemical fungicide (Captan or Chlorothalonil) following instructions
Apply chemical fungicide (Captan or Chlorothalonil) following instructions
Reapply fungicide
Reapply fungicide
Third fungicide application
Third fungicide application
Assess improvement and continue if needed
Assess improvement and continue if needed
Organic Treatment
Remove all infected parts with clean pruners and dispose in plastic bag
Remove all infected parts with clean pruners and dispose in plastic bag
Improve ventilation and reduce plant density
Improve ventilation and reduce plant density
Apply baking soda spray (1 tbsp/quart) to entire plant
Apply baking soda spray (1 tbsp/quart) to entire plant
Apply neem oil to foliage (morning or late afternoon)
Apply neem oil to foliage (morning or late afternoon)
Reapply baking soda spray
Reapply baking soda spray
Apply Bacillus subtilis as biofungicide
Apply Bacillus subtilis as biofungicide
Complete inspection and removal of new spots
Complete inspection and removal of new spots
Final assessment and preventive maintenance
Final assessment and preventive maintenance
ðĄïļ Prevention
- â Maintain good air circulation with adequate plant spacing
- â Avoid overhead watering; use drip irrigation or water at base
- â Remove wilted flowers and fallen leaves immediately
- â Water in the morning to allow foliage to dry during the day
- â Use mulch to prevent soil-borne spores from splashing
- â Keep relative humidity below 85%
- â Improve ventilation in greenhouses and indoor spaces
- â Avoid excessive nitrogen fertilization
ðą Care Guide: Golden Shower Orchid
ð§ How to Water
Water when the substrate feels dry to the touch, usually 2-3 times per week in summer and once weekly in winter. Preferably water in the late afternoon. Ensure water drains completely, avoiding accumulation.
âïļ Lighting
Appreciates bright indirect light, preferably a few hours of morning sun. Avoid direct sun during the hottest hours. Dark green, soft leaves indicate insufficient light.
ðŠī Ideal Soil
Use substrate specific for epiphytes: 40% sphagnum moss, 30% charcoal, and 30% ground pine bark. The substrate must be very well-draining to prevent root rot.