Arrgh! Powdery mildew on a new peony!

Hobbes_in_Dobbs(z5a NY)August 6, 2004

Hi there,

This is a new problem for me. I planted 14 peonies from Klehm's last year. They did great, all but two bloomed. They are in a semi-shady bed and we have had tons of rain. Well I walked out the other day and one plant (the most expensive one, of course, Carl Klehm, a real beauty) was FULL of powdery mildew. Powdery, whitish-gray-- can't be anything else (or could it?) Blasted it with fungicide--- should I continue this, or should I just cut the whole thing back? The whole plant is affected, practically.

Thanks experts!

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calistoga_al ca 15 usda 9

I have never had a powdery mildew problem on peonies but have found the only cure on other plants is oil. I use ultrafine horticultural oil. Fungicides are really a preventative and do nothing for existing mildew. Al

    Bookmark   August 7, 2004 at 9:52AM
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Pickles33(Z8 B.C.)

I am currently using the following recipe on my monarda, which is covered in powdery mildew:

2 tsp baking soda
4 cups water

Mix together & spray your plants thoroughly every 10 days.

So far it seems to be working on the new growth. Looks like my dahlias are next thanks to the high humidity we've been suffering on the B.C. Coast

Good Luck!



    Bookmark   August 9, 2004 at 8:51PM
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jerseygeorge too!!!!!!!!!!!!

Just walked past my Peonie bed and one of them is absolutely covered with what looks like fireplace ash. Leaves, stems, the whole bit. The one next to it looks fine. It's a semi shade bed.

I'll try the baking soda remedy as I research further.

    Bookmark   August 11, 2004 at 6:25PM
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Hobbes_in_Dobbs(z5a NY)

Yes, mine looks like ash oo. Still happening-- spreading to other peonies. It's weird, but there is NOTHING on all other plants!! Could this NOT be powdery mildew? On the other hand, when I started spraying all the peonies, it seemed to prevent the problem from getting worse. --Hobbes

    Bookmark   August 13, 2004 at 9:22AM
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Did the home brew per the previous post. Made sure all die off was removed completely from the bed in fall.

Peonies are now up, and appear to be up strong and lush. Just for the heck of it I gave them another treatment. Stay tuned.

    Bookmark   May 2, 2005 at 12:52PM
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I now have a peony covered in powdery mildew. I have a couple of questions:

Will the baking soda homebrew "cure" the leaves that are already infected or will they still look all white?

Would it damage the Peony if I cut off the infected foliage (it has just finished blooming)?


    Bookmark   June 16, 2005 at 2:41PM
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MizJoy(z8 OR)

Foliage that turns sooty looking is usually botrytis. Cut off affected foliage and spray w/ a fungicide like daconil.

    Bookmark   June 16, 2005 at 6:52PM
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Thanks for the lead on Botrytis. I think that is what I've got, although my peony's blooms were not affected. Maybe the infection came later. I found a link with some helpful pictures and instructions

Here is a link that might be useful: botrytis on peonies

    Bookmark   June 19, 2005 at 9:12AM
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Peony_Grower(z6 MW)

Mizjoy is correct in the dignoses........ and the treatment....

Botrytis paeoniae

Here is a website containning research from Cornell University and explains the condition and their research findings, as how to cure the promlem and the steps to take to prevent it from reoccuring in the future.

    Bookmark   June 20, 2005 at 11:07AM
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I'm brand new to this site. I too have many peonies in the same part of the garden and this is the first year that some of them are COVERED with white and I assume it is mildew. Like some others, I have some plants without any mildew at all right next to some that are very affected. I figure that some are less susceptible than others. MY QUESTION is would it do any harm if I cut down all the affected foliage and stems now instead of waiting for autumn. Do you think it will affect next year's growth and is it worth it to spray to try to eliminate the mildew this late in the season? THANKS!!

    Bookmark   August 11, 2006 at 5:34PM
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I need to know this as well (Mimika9's post), re: cutting down before fall, and spraying now, in August. I write this a year later than the previous post, but I have the same questions! (Help?)

    Bookmark   August 17, 2007 at 9:23PM
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