If you're dropping 200 mites in 24 hours this time of year, chances are your hive won't make it to spring if you don't do something quickly. Oxalic acid is by far your best choice. With that many mites dropping, your bees must be raising brood. Trickling OA, though fast and easy will kill any open brood. Vaporizing is your best bet, do it once a week for 3 weeks. Doing it right takes a bit of practice, and a lot of care so as not breath the fumes. It's not without risks. Use common sense.