It isn't scale. I'd say spidermites and I believe I can see a cast aphid skin too.

I see a cast skin too i believe. Im in florida as well and i try and do a weekly cfoliar spray of compost tea on my cut flower. Helpa pretty well to keep pest at bay.

Also im going crazy yrying to find dahlia tubers. Where in FL are you. Any cuance u can sell any?

No that's definitely not spider mites but I do have them! I'm pretty good @ identifying insect probs - but NEVER seen scale on dahlias b4! I do believe it's scale. I didn't kno dahlias can be affected w/scale but in Florida anythjngs possible!! I don't mean to sound rude or mean in any way floral but mites don't cause raised spots like this underneath the leaves that are hard to scrape off . It causes more of a dirty, dusty look w/white glistening on the leaf plus, if u look close or the infections bad enough u can actually c the mites- even more so when it's the 2potted mite. I do believe it's a type of scale. Not armored but a soft scale. I do appreciate your feedback. CICI - I did purchase quite a bit of neem & diatomaceous earth & I have avid for mites. But bc it's well over 90• during the day & being in fla, if I use oil based spray - it automatically burns the leaves no matter the strength :( I'm trying to use only organic methods though so I disposed of the infected leaves.I'm getting so much insect damage, it's sickening!! Flower & chili thrips, earwigs, mites & leaf miners are taking over my dahlias !! Ugh!!

Sol y mar farm - I was born n raised in st pete fla my whole entire life but moved to a more country setting out on 3 acres in Brooksville Florida zone 9 in central fla on the west side :) where r u located?? I went crazy & bought 42 tubers & this is my first year getting " serious" with growing dahlias. I will b more than happy to give u a few! Email me anytime :) :) :) Crossrachel@icloud.com

Spray garlic water onit it always works for me