I find conflicting advice about whether to treat all hives in the beeyard at once for varroa, or to treat piecemeal. The guidance for Formic Pro says to treat all at same time. The state apiarist says to treat each hive only when mite counts reach threshold. It seems to me that it's a given, at this time of year, that mite numbers are going to increase, after the flow has ended. That's just the life cycle of mites in bee colonies.
It's a fine threshold between finding 2 mites in a sugar roll and finding 3. Three is supposed to be the threshold for treating, in my area. I am inclined to go ahead and treat all hives, with the expectation that waiting will only cause an increase in numbers. Of course, that way I will lose the possibility of hygienic behaviors keeping mites in check.
Temps this time of year are usually too high for using Formic Pro, and we're having a nice little cool break over this week, so I'm inclined to treat all while I can, knowing that it may get hot again and then treatment will be impossible for a month. Asking for folks' opinions based upon their own experience. TIA.