from what I can make out it could be woolly aphid. is there an insect inside the fluff?

but it could be a different bug as you are in the US.

Thank you!

I was thinking powdery mildew, especially since it appears to be a Phlox plant.

when I enlarge it as much as I can it looks to be 'raised' that's why I thought of woolly aphid. could be mealy bug as that has the 'furry' layer too.

I see what you mean, Sbg. I didn't enlarge it enough, when I looked earlier. The white debris on the mulch to the right is particularly suggestive of either mealybugs or woolly aphids. In either case, you will need a surfactant of some kind to help the insecticide get through the "wool". It's very convenient than most surfactants, such as soap, will help control powdery mildew! :)