Good question! It normally makes sense to treat all colonies in a yard for varroa mites at the same time as long as all the colonies are in a suitable condition for treatment. Sometimes it makes sense to skip/delay treatment for colonies. For example, some nucs or small colonies may be too small to handle a formic acid treatment (and treating them would be inconsistent with the treatment's label). Or, you may want to avoid opening/disturbing colonies that are in the process of requeening.

Since you have five colonies that you seem to track closely, I think it makes sense to delay treatments for colonies that are requeening. The brood break from requeening should help delay varroa mites from reproducing. You could consider an oxalic acid or other treatment in the colonies that are requeening just after the new queens have started laying (before there is sealed brood, so  the varroa mites are all exposed on adult bees). Or you may figure that brooks breaks from requeening are sufficient varroa mite management so far into the season.

Happy beekeeping!

Thanks.  I will hit with OA dribble as suggested...If my timing is correct, mating flights are happening now, so should have open brood this weekend...

Sounds like a plan!

Follow up on OA dribble...Can you do a OA dribble more than once...i.e. every 7 days since there is capped brood?   I recall hearing that the dribble method is harder on the bees than the vapor, and to limit how often you do it...

Mainly asking is hive is too small/weak for FP treatment and for top bar hives (neighbor has one and not sure how to treat for mites)...

Thanks for reaching out! I apologize that I wasn't able to answer your question sooner.

As you know, applying ApiBioxal (oxalic acid) as a solution method (dribble) only kills varroa mites on the adult bees; it does not kill varroa mites reproducing underneath the cappings of the honey bee brood.

Applying oxalic acid every so many days may not effectively control varroa mites because you can still expect to miss varroa mites. We know that some varroa mites emerge from brood cells and then almost immediately enter new brood cells for reproduction, so treating every 7 or so days would miss mites that are behind a brood capping for each treatment.

Oxalic acid's mode of action (how it kills varroa mites) isn't known, and there may be unknown effects of using the same treatment multiple times in the same colony. Rotating different treatments can help reduce the risk of varroa mite resistance to oxalic acid.

For the top bar hive, I'd be inclined to combine an oxalic acid treatment with a brood break. The beekeeper could cage the queen (and subsequently remove any queen cells the bees build), and then time the oxalic acid treatment for when there wouldn't be any capped brood in the hive. Applying oxalic acid when all of the varroa mites are exposed on adult bees should greatly increase its efficacy (as opposed to treating when there is sealed brood present). The beekeeper could also time oxalic acid treatment during periods of intentional or natural requeening when sealed brood is not in the hive.

For the nuc that is too small/weak for a Formic Pro (formic acid) treatment, you could apply oxalic acid when there isn't sealed brood present for maximum efficacy. You could also consider HopGuard III, which can be used for smaller colonies. (Note that in my experience, HopGuard III can kill brood that touches the strips.)

Hopefully we will have new, longer-lasting, oxalic acid varroa mite treatments approved for use in Michigan soon.

Happy beekeeping!

Thanks,

I understand the OA dribble does not kill mites in capped brood.   I also rotate my treatments.   The OA were on hives that had a brood break and were weak.  Hopefully by late August they are strong enough for my second round of Formic Pro treatment.  I will then put Apivar strips in sometime in October after I pull honey.  I usually then do an OA dribble right before winter to clean up any leftover mites...

As for the Top bar hive, I told my neighbor she should consult with other beekeepers who use them and see what they do.   Will forward your recommendation to manipulate a brood break (or take advantage of natural break) and hit with OA dribble when no capped brood.