That's exactly why there are resistant mites, these yahoos keep using the same stuff over and over and worse, use it as a *preventative*.yea mites will become immune if you use any 1 spray. You got to switch it up & mix sprays to make it more effective.
If that 'white stuff' wasn't Floramite, it was probably FORBID, which gives me a 1 application wipe out of mites. I also have Floramite to alternate with it, but as of yet, have never needed it.
I used to be a licensed applicator, and Forbid is the best miticide I've seen in over 30 years.
Wet