I use OAV and Apivar.
1st i test by doing an alcohol wash to determine when to treat and to see if my treatment was effective. I treat all hives in the yard. My OAV treatment is every 3 days for 7 treatments. That seems to knock them down and it has never had a negative impact on the bees. I just finished that. The last week of September I will add Apivar for 45 days.

I will also add that the only hives that I couldn’t control with OAV were my Saskatraz hives. I just couldn’t keep them as low as I like. I think it is because they had massive amounts of brood all the time.

I do an alcohol wash on random hives starting in March and do it every other month or so.