Powdery Mildew

Asked September 2, 2020, 3:01 PM EDT

My peony bushes have powdery mildew. They are right in front of the anemones in my flower garden that are just starting to bloom.

I now realize from looking at previous questions, that it is over-crowded and in a shady area which helps the spread of this disease. My original thought was that the peony foliage would have died down enough so the anemones would be easily seen behind it.

At this point should I cut down the peony foliage so it won't transfer to or otherwise affect the anemones? It doesn't like it has so far. Thank you.

Anne Arundel County Maryland

1 Response

In general Japanese anemone is susceptible to powdery mildew but we have not received questions or photos on this. Anecdotally several of us have Japanese anemones and we have not seen powdery mildew on the plants.

Peonies - Cut down all infected foliage now and get rid of this infectious material. Next spring, monitor your peonies, and as soon as you see one infected leaf, pull it off. You will have to decide it you want to spray a fungicide or a horticultural oil labeled for powdery mildew or tolerate it. Fungicides are preventative--not curative. They will halt further infection, but cannot restore infected leaves to health.
You do not have to spray and there are no resistant peony varieties.

Powdery mildew has become a bigger problem on peonies the past few years. Make sure there is adequate sunlight and good air circulation to reduce humidity levels. Allow proper plant spacing for the same reasons. Pruning for better air circulation also may help. Practice good sanitation.

Here is our website info on powdery mildew: http://extension.umd.edu/hgic/powdery-mildew-annuals-bulbs-groundcover-perennials-and-vines
and peonies https://extension.psu.edu/the-beloved-peony

Marian