Powdery mildew is a common fungal disease that appears as a white or grayish powder on the leaves, stems, and buds of many plants including euonymus (pictured below), crabapples, ninebark, peonies, roses, and zinnias. It thrives in warm, dry environments with poor air circulation. While rarely fatal, it can stunt growth and reduce flowering unless treated with proper cultural practices or fungicides.
