Hi Deanna, this is Peggy. Sorry you are having white mildew on the leaves of your peonies. Hope this information is helpful. Causes of White Powder on Peonies. Powdery mildew is caused by a fungus. ... However, most species of powdery mildew can germinate with or without water—though humid conditions are quite common for growth. Other ideal conditions for powdery mildew are moderate temperatures and shade, which generally spawns moisture.Mar 28, 2019
Causes And Treatments For Powdery Mildew On Peonies
Spray it with milk.
I think this video might answer your question. https://youtu.be/VCeGZnoIKhc
Thanks for the info.