A fungal disease causing a white or gray powdery coating on leaves, stems, and flowers, favored by warm days, cool nights, and low humidity.
Powdery mildew is a white fungal coating on foliage that looks dusty. Unlike other mildews, it thrives in dry conditions (hence the name—no moisture needed). It reduces photosynthesis and is cosmetically unattractive but rarely kills plants. Prevention through air circulation and resistant varieties is most effective; fungicide sprays (sulfur, neem) can control it if severe.
Powdery mildew is common and preventable. Understanding prevention prevents need for spraying.