These diseases can infect the canes and reside in the lesions over the winter. Recognize powdery mildew by the curling of young leaves, purple to black discoloration of leaves, and white mold on leaves, buds, and canes. Prune lower on canes to reduce the number of overwintering lesions. Destroy or discard fallen leaves and prunings. Space and locate plants to encourage rapid drying of leaf surfaces.
Many insects feed on roses.
Japanese beetles, rose chafers, and several caterpillars chew rose leaves. Other insects, such as aphids, thrips, leafhoppers, and rose midges, can seriously weaken rose plants or damage buds by feeding on plant juices. For specific recommendations on these potential problems, always check with Cornell Cooperative Extension - Suffolk County because this information may change over time as new, more effective pesticides are developed and old ones are discontinued. In New York State winter protection is necessary for garden roses. No better method has been devised than mounding soil around the base of each plant to a height of 10 or 12 inches.