So lets get past the "it's not approved in the US for beekeeping" thing right off. I know, but if I want to treat my hives, they are my hives.
After much study, the 2 most common methods of application seem to be Vaporization with a heating unit inside the hive or the Dribble/Drench method. Both require accurate measurements of how much OA is being applied to a given size hive. Both methods only work on phoretic mites and both seem to be reasonably equal in effectiveness.
The vaporizers run $100/200 dollars and require you to lug around a car battery for power. At best, they take a few minutes per hive to heat up then cool down. Not a huge deal but still a long day if you have very many hives.
The dribble method requires a partial disassembly of the hive and dribbling between each frame of the entire hive. A huge amount of labor. I wont even consider it.
Which brings me to the propane fogger.
My plan is to buy a new fogger. My current one has been used for insecticide and I dont want to try to clean it out.
Next is to figure the calibration of the trigger pump. I can immerse the pick-up tube in a graduated cylinder and measure how much liquid is dispersed with each pump of the trigger. Lets say for example 20 pumps moves 200ml water, then it is 10ml per pump. This is easy to check periodically to maintain my calibration.
Next, make up a solution that would have water and OA in a concentration that would give for ex. 1gram of OA per 4 pumps.
The common dosage of 1 gram per brood box can be administered quickly, 4 pumps, from the front of the hive opening then closing the hive with an entrance closing block. Nucs get 2 pumps, you get the idea. I could change the concentration of the solution to suit my needs as long as I know how much solution is dispensed with each pump.
It does not appear to matter what form the OA is in for it to work in the hive but it appears critical that it be evenly distributed throughout the hive. The vaporized is a very small fume particle and the dribble is a water/OA/sugar solution droplet. The fogger would deliver a very small water droplet throughout the hive.
The added moisture would be bad for the hive when cold but on a really warm late fall day when the hive is mostly broodless I cannot see how the moisture from the fog will have any adverse effect.
I have search the web and have not found any examples of this delivery method except a German Youtube video showing an air compressor/forced air type fogger on a wand.
I did treat this fall/winter with the "crack pipe" method. Just figured there had to be a better way.
I expect to be doing this in the coming year and will document my findings for posting here on Beesource.
Like many of you, I am working towards treatment free beekeeping, but right now, a little treatment is necessary to have bees to keep.
Your thoughts and suggestions are greatly appreciated.