Does oxalic acid leave long term residues in the hive?

[beekuk]

I wouldn't recommend oxalic as your only method of treatment if varroa levels are high in summer.

I would not recommend, or use oxalic acid via the trickle method at all,if you really need to use this, then your earlier treatments have failed,and any young bees may very likely have been badly violated by the mites, and their associated viruses.

[Mike Gillmore]

The problem I see with the single trickle method in the Northern US and Canada is that the recommendation is to apply only one treatment in the broodless period, late in the season. By then the damage has already been done, many times it's too late if the mites loads are very high. The treatment may have terrific efficacy at that point, but bees stressed by heavy mite infestation are already in decline and will struggle to make it through winter.

I like the two pronged approach. In late summer when the mite levels are skyrocketing treat with OA Vapor, 3 treatments one week apart. This will knock down a fairly high percentage of phoretic mites and allow for a healthier colony moving into late Fall/early Winter. Then when they are broodless treat with a single trickle of OA to clean them up.

[kjbann]

The problem I see with the single trickle method in the Northern US and Canada................ In late summer when the mite levels are skyrocketing treat with OA Vapor, 3 treatments one week apart. This will knock down a fairly high percentage of phoretic mites and allow for a healthier colony moving into late Fall/early Winter. Then when they are broodless treat with a single trickle of OA to clean them up.

Mike,
What would be wrong with using vapor for the late year treatment as well?
Ken

[danno]

I agree completely with Mike and using vapor for a late treatment is not a problem to answer kjbam's question. I treat just as Mike does 3 times a week apart in late summer and have a few mite free brood cycles before winter sets in. I use a 12 volt burner with 25 foot of cord, wood bleech and NO resporator because I'm 25 ft away during the burn. I also do another 3 rounder in late spring. 3 treament 2 time a year does take a bunch of time but little money. I dont have a mite problem on my colonies. The mites do have a Dan problem though

[Mike Gillmore]

Mike,
What would be wrong with using vapor for the late year treatment as well?
Ken

Nothing at all, I'm sure that will work very well also. But I think there may be a general opinion, which may or may not be accurate, that Trickle is more effective on a broodless colony than Vapor would be.

I guess my main point is that in some areas of the country relying on a single trickle in late fall/early winter may not be enough if nothing is done to knock down mite loads when the numbers skyrocket in late summer. I've seen the difference, the mites really need to be dealt with when their number peak or the colony suffers terribly going into winter.