The presence of a white, dusty mildew on infected plant partsmakes powdery mildew easy to diagnose. Late in the season, tinyblack fungal fruiting bodies may appear on the mildewed surface.
Powdery mildew can occur on leaves, stems, buds, and flowers.
Ornamental plants that commonly show signs of powdery mildewinclude lilac, viburnum, crabapple, phlox, rose, zinnia, begonia,and turf. Powdery mildew is favored by cool nights followed by warmdays. The disease is most common in shaded areas and in siteswhere plants are crowded and air circulation is poor. Keep plants properly spaced and pruned to promote good aircirculation. Plant where sunlight will be adequate.