Re: Is it tougher and tougher to control mites with OAV?
I find with two OAVs during no brood period in late fall and Apivar in early spring, mites are very minimal. This is consistent with what Ian Steppler is finding. We do have a distinct winter for 5 months. I did a OAV and installed a sticky board for 4 days to check mite infestation in early Sept and counted less than 10 mites per hive.
Vaporization is the only practical way(IMHO) in late fall. Opening a hive and exposing both brood boxes and dribbling a wet syrup is not good. One needs to dribble each brood box to get an effective control. One is also breaking propolis seal.
I use the Varrox on my four hives and time is not a factor. It takes 30 mins tot at each location, as there is two hives at each location. There is little vapor exposure when one is standing 10 ft away, so very safe to use.
If I had more hives, a band heater type vaporizer and vapor mask reduces would be the next logical step as the time is 30 secs per hive.
Zone 3b. If you always do what you always did, you'll always get what you always got!