Cymbidium Crisis: Diagnosing and Treating Snow Mold Root Rot

Identifying and Managing Snow Mold in Cymbidium Orchids

When a mature cymbidium suddenly collapses with rotted pseudobulbs, white fungal mats, and water-repellent root balls, the culprit is often snow mold (Ptychogaster species)—a hydrophobic fungus that seals roots from moisture.

Diagnostic Signs of Snow Mold

• White, water-repellent fungal mat covering roots and media
• Sudden wilting despite wet media (fungus blocks water absorption)
• Progressive pseudobulb rot from center outward
• Healthy-looking outer pseudobulbs initially

Treatment Protocol

1. Complete unpot and root washing—remove all media
2. Excise all rotted tissue—cut to firm, healthy pseudobulb
3. Fungicide treatment: Terraclor (PCNB) or Turfcide drench per label
4. Root healing: Air-dry cut surfaces 4 hours before repotting
5. Repot in fresh, well-draining cymbidium mix (coarse bark, perlite, charcoal)

Preventing Spread to Collection

• Inspect all cymbidiums for early signs
• Quarantine treated plant 4-6 weeks
• Improve air circulation—critical for prevention
• Avoid overwatering; allow near-dryness between waterings

Heat Stress Management (Bonus for LA Growers)

Leaf sunburn during Santa Ana winds:

• Mist foliage (not soak) to cool leaf temperature
• Target: leaves should feel cool to touch
• Fog-it nozzle (0.5 GPM) or dedicated misting system
• Multiple daily applications during extreme heat

Local Resources

Southern California growers benefit from:

• Costa Mesa Orchid Show (Orange County)
• Huntington Gardens Sale
• Santa Barbara International Orchid Show (March)
• Specialty nurseries for Terraclor/Turfcide access