mildews

Mildews are a group of fungal or fungus-like organisms that colonize damp, organic surfaces. In gardening and horticulture, mildew commonly refers to two types of plant diseases: powdery mildew and downy mildew. They are related in appearance and ecology but are caused by different kinds of organisms and have distinct symptoms and lifecycles.

Powdery mildew is characterized by a white to gray powder on the upper surfaces of leaves, stems, and buds. It favors warm days with moderate humidity and good air circulation. As it spreads, photosynthesis declines, and affected tissues may become stunted or distorted.

Downy mildew is caused by oomycetes such as Plasmopara or Peronospora. It typically forms pale or yellow patches on the upper leaf surface with a fluffy, downy growth on the underside. It often requires leaf wetness and poor air movement.

Mildew in buildings refers to mold or mildew growing on walls, fabrics, or other moist materials. Indoor mildew may produce odors and can trigger allergic reactions or asthma in sensitive individuals; the health risk depends on the species and exposure level.

Prevention and control focus on moisture management: reduce humidity, improve ventilation, and fix leaks. Remove and dispose of heavily infected plant parts. In gardens, use resistant varieties and appropriate fungicides. For indoor mildew, clean affected surfaces with detergent and water and consider diluted bleach or specialized cleaners, after ensuring it is safe for the material.