Peony has powdery mold (?) - Ask Extension
Hi, I have 3 peony plants in a very sunny site. Attached are some photos of the powdery white stuff that is all over 2 of the plants and spotting the ...
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Peony has powdery mold (?) #656119
Asked June 25, 2020, 5:19 PM EDT
Hi, I have 3 peony plants in a very sunny site. Attached are some photos of the powdery white stuff that is all over 2 of the plants and spotting the third. The blooms were great this year--maybe a little small, but prolific. Maybe the plants are getting too crowded? The plants have had this powder in previous years but much later in the season and not as wide spread.
1. should I respray with milk/water? (it seemed to make a small difference)
2. can I cut them down now? the powder seems to have spread to an aster and some golden rod. The butterfly weed nearby doesn't seem to be infected. I don't want it to spread to the rest of the garden.
3. Is there any harm to chickens or people if this powdery stuff is blowing around?
4. should I thin the peonies? The leaves seemed extra thick this year.
Thanks for your help!
3.
Ramsey County Minnesota
Expert Response
The following documents contain reliable information about powdery mildew. They will probably answer most of your questions.
1. If you think milk spray is beneficial there is no harm in using it.
2. Do not remove the peony leaves now. They are needed to store energy for the next growing season. It's OK to remove them in late summer for aesthetic purposes.
3. There are many strains of powdery mildew. What's on the peony may not be spreading even though mildew is present on other plants in the vicinity. Experts at the Connecticut Agricultural Experiment Station put it this way, "Although the symptoms of disease are similar, the fungi responsible for powdery mildew fall into a number of different genera including Erysiphe, Leveillula, Microsphaera, Sphaerotheca, and Oidium. These fungi are all obligate parasites that require living hosts in order to complete their life cycles, so they readily infect healthy, vigorous plants. Some powdery mildew fungi have broad host ranges whereas others are fairly host-specific. For example, the powdery mildew fungus that infects lilac is not capable of infecting cosmos and vice versa. However, the powdery mildew fungus that infects oak can also infect rhododendron and dogwood."
3. So far as we know, powdery mildew does not affect the health of people or other animals.
4. Thinning the peony vegetation may be beneficial. It's consistent with the bulletins' recommendations.
