Dark, streaky lesions may also be present on the stems of either tomato or potato. The disease can be controlled in the home garden by picking off diseased leaves and using fungicides such as chlorothalonil or mancozeb that are approved for use on garden vegetables. Severely infected plants should be removed from the garden. Many brands of fungicide with these active ingredients are available from garden centers and discount stores. Applications as often as every 7-10 days may be needed during periods of cool, wet weather.
Powdery mildews are often severe on lilac, phlox, roses, and Monarda.
They also occur on many other hosts. Powdery mildews are easily recognized by the dusty, powdery appearance they cause on leaves of their hosts. When severe, powdery mildews can cause deformation of the leaves. Roses and other plants that have green stems may also be infected on that plant part. Powdery mildews will also colonize flowers and buds on rose, causing color breaks on flowers and bud abortion.