I have doubts whether it was the mildew that was the cause of the fallen leaves. Such a serious devastation in such a short period of time indicates that the plant was severely stressed. Most probably it was too thirsty for too long time. Plants growing in too dry conditions will be attacked by mildew more severely.

That does seem like a very sudden onset of mildew. When mine get mildew it usually slowly worsens over the season. So far this year, there is no mildew on my red NOID and Raspberry wine, which is nice.

Monarda didyma and its cultivars need a rich and consistently moist soil, along with good air flow. I also give mine a haircut in June and trim back about half the stalks. This staggers the bloom and might help encourage better airflow.

I think you can try cutting them all the way down, give them some compost and water, and they will probably regenerate through the summer. Someone on the New England Gardening forum said they got them to rebloom this way.

Its been hot and dry in the DC area. My hedge of Raspberry Wine is naked from the waist down. Fortunately I have other stuff planted in front to camouflage it. I think your plant is heat stressed --- water and a haircut should help.

Thanks for your responses! I'm new to growing Monarda, so how much water do they need? The soil is damp just under the layer of shredded hardwood compost and the foxglove and hydrangeas in the same bed are seemingly doing fine. The bed gets morning sun and then dappled shade the rest of the day.

Heat stress does make sense given our weather and the fact that of the two plants, the one on the bed's outside edge that gets more sun is the naked one.

I finally dug out all of the Monarda that I had because I couldn't stand the PM it always got after it was finished flowering plus the plant simply looked ugly after flowering. I am not a fan of the foliage. My gardens have drip hoses installed under mulch and all other plants around it did well. Nothing I ever did improved its appearance. In flower it was lovely, but afterward it was awful.

Zoecat, it seems to do okay with medium-moist soil and does really well in part sun. Since I have practically NO full sun in this yard I'm grateful when a plant thrives in part sun.

Yes the foliage can get ratty looking, but Monarda is not the only perennial that gets ugly foliage by any means. It's hard to have a perfect looking garden all season long. I wouldn't be without it, it's so beautiful and the pollinators just love it. My red Monarda is just starting to bloom and the hummers are already checking it anxiously.