I have noticed this year that 2 of Saunder's hybrids seem to be prone to mildew:
Paeonia 'Roselette', Paeonia 'White Innocence'

Anyone else notice any cultivars or hybrids that are prone to mildew?

I've had more mildew this year than most but it's been a fairly stressing year, bad hail storms, very hot, dry summer then lots of rain/hail end of summer. All of the herbaceous seem to be affected, no issues with trees or Itohs.

My former Roselette always developed a mildew appearance long after blooming, usually in late summer. Never affected the next year performance,

Both my 'Roselette' and 'White Innocence' are new, planted last fall, did not develop any mildew this season like all other peonies. I don't mildew on peonies at all, only on delphiniums and globe flowers here.

I walked my gardens this morning specifically looking for mildewed peonies. 'Roselette' and 'White Innocence' seem to be the only ones out of 160 peonies. However, most of my peonies are starting to turn brown or blackish. It's actually time to trim them to the ground.

Note, I usually have several peonies that mildew. However, I have not kept a record of the ones that did.

My Roselette was the first to have PM and was the first to be pruned this year.

Copper Kettle is the only cultivar I have that is prone to powdery mildew.
Never seen it on any peony I own.

Frank,
It is very common on many of my herbaceous. Now is a good time to start cutting back foliage and removing it far away from your garden.
I have never seen problems arise the following year for any that experienced mildew.

Bump