Hi, 

We are seeing a lot of powdery mildew (on flowers) and powdery mildew (on trees and shrubs) this spring which could be due to the fluctuating temperatures and rain events. Warm humid days and cool nights. Generally we don't recommend using a fungicide because the symptoms are rarely lethal to the plants. It is also hard to control given it comes back with the right weather conditions. You could wait for them to bloom and then prune down to the ground or thin out to add air flow and to help get ride of the spores. This will hopefully keep it from transferring to another susceptible plant. Horticultural oil works for powdery mildew if you decide it is necessary. Just check the label for application and use. 

Emily