How to Treat Powdery Mildew on Roses
Treat powdery mildew by improving airflow, removing affected growth, and watering at the base. Its white coating thrives on stressed, crowded plants; a fungicide or a baking-soda spray helps, and resistant varieties prevent it entirely.
Powdery mildew appears as a white, powdery film on new leaves, buds, and stems, curling and distorting growth. Unlike most fungal diseases it favors dry days and humid nights, and it spreads fastest on crowded, shaded, or stressed plants.
Manage it by spacing plants for good airflow, removing badly affected shoots, and keeping roses well watered so they are not stressed. A fungicide or a homemade baking-soda-and-horticultural-oil spray checks active outbreaks. As with black spot, the durable fix is to grow disease-resistant varieties.