I have 11 colonies of various configurations in my one apiary. Some of the queens are this year's locally raised mutts, a couple are saskatraz, and who knows for the rest (I got them "used").
Here is my fall OAV treatment schedule this year, all colonies treated the same - August 11, August 31, September 7, September 13, September 20, September 24, September 30, and October 5. I shoot for 5-7 days between treatments (other than the one on August 11), but you will see some variance.
My OA is sourced from Florida Labs, and is "in date" and kept sealed, and looks clean. My OAV wand is a cheap one I bought from ebay, but seems to work fine. I see vapor when I treat, and mites die.
Most of the hives have mites largely under control now, as I am seeing just low double-digit drops after the last couple of treatments. But 3 colonies are dropping far more than I care to count, posssibly in the low hundreds 3 days after the September 30 treatment. Pulled the boards out for a glance today, and it looks like we are tracking for about the same this time as well.
At this point I suspect that I should have done something other than OAV, possibly Formic Pro, so that the treatment would be more prolonged. But each time I think "this is likely the last time for this year," and then it is not.
All colonies are strong and active. I suspect they may be robbing someone else's hives, otherwise I cannot explain what is going on.
Anything else I can do, or anything I have missed, that I can do better next time?
For those who might want to suggest just letting them die - it's not gonna happen as long as I can help it. I am solidly on the treatment side of the fence in my location and circumstance.