Previously, someone had posted pictures and comments about a gray substance on their peony leaves. This is Roselette in the beginning stage of the same thing. It will completely turn the foliage gray at about the time it turns dormant. Never appears to damage the plant since it comes back better each year. I usually cut Roselette down before the others.

This is the same Roselette. The foliage has reached the stage where it no longer provides food for the storage roots. It can be cut down anytime.

I have never gotten it on my peonies but always on my Siberian pea bushes, geraniums (the large blue kind), and the delphs. Pretty unsightly and the Siberian Peas also are afflicted with something that eats the leaves down to sticks similar to the worms that do it to the columbine. But unlike the columbine which I cut to the ground and then come back sans worms, I have lost an entire 10' section of my hedge of SP.