> I would be interested in hearing more about whether he feels his use of oxalic acid was helpful or harmful to his bees.
I did not see any harmful effects by oxalic acid vapor directly on the bees. I am concerned about the effect on the microbes in the hive. Shifting the pH dramatically has a very marked effect on what microbes live and what microbes die. Microbes have a very marked effect on the health of the bee and of the colony:
As a treatment it was very effective (I was vaporizing). As far as keeping the honey clean, there is already oxalic acid in honey and research shows little change in that amount. But as far as maintaining the natural balance of the hive, I have serious concerns.
What I liked about it was it was not dependent at all on ambient temperatures and it was very devastating to the Varroa population and it could be repeated as often as you like, so once a week for three weeks was a doable thing if you wanted to treat while there was still some open brood.
Dribbling would be even more devastating to the microbes in the gut of the bees which are protecting them from Nosema, AFB, EFB and Chalkbrood and are needed to inoculate the bee bread and probably to the bee bread itself.
Back in the 60's when I first started reading about beekeeping and back in the 70's when I first started keeping bees, beekeepers were all adamant about the pesticide treadmill that agriculture was on and how it never allowed things to balance out because you keep killing the predator insects along with the pests and that the problem would never be solved as long as you kept doing this... funny how quickly they all abandoned the concept when the mites showed up...