9ac1836f_Pests___Diseases__Problem_Symptom
[Cause] Powdery mildew, a fungus disease carried by wind. The problem is most severe when nights are cool and humid, and days are warm and dry. [Solution] Remove and destroy all infected leaves, including those on the ground. You will probably only have one or two varieties of roses that are susceptible to powdery mildew. To prevent mildew or to arrest its spread, spray with a fungicide starting in early summer. [Problem/Symptom] 
Leaves, especially new leaves, become twisted or curled and are covered with a white powder. Flower buds and canes may also be affected.
Pests & Diseases
Problem/Symptom