I replanted these small peonies plants from a shady area to a sunny area near our house. But for the second summer in a row, they have severe mildew on them. Neem oil did not prevent it. From what I have read, once it starts you can't stop it. What should I do at this point. It is only the end of May. So should I remove the foliage, and burn it? Should I just leave it? Or should I remove the diseased plants and put in new healthy ones? If I put in new ones, is it dangerous to put them in the same area?
Persistent Powdery Mildew on Peonies
Certified GKH Gardening Expert
This link will help you with more information.
You can look for cultivators that are resistant to Powdery Mildew.
I have this issue with my Bee Balm in my garden and though I could tear them out and replace, I have had luck with spraying them with Neem Oil every 2 weeks from the time they emerge from the soil.