Mildew

Mildew is a term used to describe certain types of mold or fungi that grow on damp surfaces, producing a characteristic powdery or downy coating. It is not a single organism but an umbrella for several fungi and oomycetes that thrive in moist environments. Indoor mildew commonly appears on walls, ceilings, bathrooms, fabrics, and upholstery, while plant mildew affects many garden crops and ornamental plants.

Environment and appearance: Mildew needs moisture, moderate warmth, and limited air flow. On plants it often shows as white or gray powdery patches on leaves (powdery mildew) or yellowish, downy growth on the undersides (downy mildew). On building materials it appears as fuzzy or flat patches that can be gray, green, or black.

Health and impact: Exposure can provoke allergic reactions, coughing, sneezing, and eye irritation in sensitive people. It can worsen asthma. Mildew itself is usually not highly toxic, but it indicates ongoing moisture problems that can cause material damage and mold growth.

Prevention and control: Reduce moisture and improve ventilation; repair leaks; use dehumidifiers to keep relative humidity below about 50-60%. For nonporous surfaces, clean with detergent and water; for painted surfaces, wipe and repaint with a mildew-resistant product after cleaning. Porous materials such as drywall or insulation may need removal and replacement. On plants, increase air circulation, adjust watering, and apply appropriate fungicides if needed.

Safety and environmental: Wear protective gear when cleaning, avoid dispersing spores, and follow product instructions. Large infestations or structural mold requires professional assessment.