Downy mildew thrives in cool, wet weather.
Downy mildew can kill canes so rapidly that they wilt overnight.
Botrytis, a gray mold, attacks buds and flowers. There is no cure for rose mosaic, a viral disease. The viral disease rose rosette is spread by mites. Galls can grow on the stem, root or crown of the plant. Canker can spread down or around the stem, causing dieback.