I had Raspberry Wine in a part shade location and it had terrible powdery mildew. I moved it last fall to a full sun location and though it has really thrived this year, it still ended up with powdery mildew….just not as bad as last year. Nature of the beast, I guess. Maybe there are powdery mildew resistant cultivars.

Some plants are just prone to PM.....bee balm is one. So is garden phlox, ninebark and most squashes'

There are a few PM resistant cultivars of monarda. Fine Gardening has done a good evaluation.

I only grow 'Jacob Cline' because I like the color (and so do the hummers) and the height. But although it is only rated as fair', I have never experienced any PM with it.

Is it located in a damp spot or does the soil dry out? My raspberry wine doesn't PM unless severely drought stressed.

because that is what they do as they shut down for winter ... it is sept.. and in a few weeks you can just cut them to the ground.. and stop looking at them ...

id wait until its a bit colder.. just to insure i didnt stimulate new growth with only a month or so before frost ... that would just be a waste of stored energy it needs for next spring ...

you have repeatedly noted drought in your garden this season... so cecily is spot on ... stress is stress.. and it always amazes me.. how bugs and disease.. can find already stressed plants to attack ..

ken

I have "Jacob Cline", its second season in the ground and has gotten PM both years. It's not in an in-your-face spot, so it doesn't bother me, and it hasn't spread to other plants. I also have wild bergamot (Monarda fistulosa), I bought it full well knowing it usually gets PM but surprisingly it didn't while the "Jacob Cline", which is supposed to have some disease resistance, did. Go figure {shrug}.

I've tried about 5 different varieties of Monarda, including Jacob Cline and all from lists of the least prone to mildew, grown them in full sun and kept them well watered and they all got PM. I'm considering growing them in an out of the way location that is not front and center just for the hummingbirds and ignoring the PM.