Common Houseplant Diseases: Gray Mold, Powdery Mildew, Rust & Viruses

Fungi cause most houseplant diseases. Early detection and targeted action prevent spread.

Key Diseases

• Gray mold (Botrytis): Fluffy gray mold on dead tissue, spreading to live parts. Favored by damp, cool conditions (fall). Remove dead material promptly; ventilate; avoid late-day watering.
• Powdery mildew: White powdery patches expanding to cover leaves; foliage yellows/drops. Favored by hot, dry conditions. Neem oil and fungicides help.
• Rust: Pale circular spots on leaf tops; rusty brown spore rings underneath. Affects pelargoniums, carnations, chrysanthemums. Difficult to control.
• Plant viruses: Mottled/mosaic leaves, malformed growth, poor color. Spread by aphids. No chemical cure—discard infected plants.

Prevention: sanitation, airflow, proper watering, and pest control.