I tried fogging with 10% oxalic acid dissolved in water.  I fogged ten five over five deep nucs once a week with 0.6 g of oxalic acid
dihydrate for each five deep for eight consecutive weeks this summer.  I had  ten nucs untreated side by side for controls.  The single highest
after treatment mite count was from a treated nuc determined by alcohol wash at 3%.  I saw exactly zero evidence that I killed any significant number of mites.  Overall the treated hives and controls had equivalent mite counts.  All were at 0 to a bit over 1% mites at the start.  I dosed as high as 2g/ five deep nuc and showed no adverse effects other than a few burned bees that hit the fogger screen.  Fogging ran from mid June
 to late July.  All were treated earlier in the spring to drive mite counts to about zero with apivar.  The slow build up by early August is because I run Minnesota Hygienic queens which do a fair job of containing mite populations.
 
 I was pretty careful in the experiment.  I spent several hours fooling with the fogger to figure out how to deliver a consistent dose.  I had to drill a hole in the top of the handle and push down the trigger fully down with a screw driver after each shot to get consistent volume each time.  I also had to pull the trigger as fast as possible to get consistent volumes.  I showed, by capturing and analyzing the fog that oxalic was surviving the fogging experience at least partly intact.  My capture was under 100% and analysis showed a recovery of 60% so I feel was I was not
decomposing enough to matter.
 
I also waited 20 seconds between trigger pulls to allow full heat recovery in the coil.  Even then a lot of what came out the spout was liquid that ended up on the bottom of the nuc.  I found the process tedious and not really all that fast at over three minutes per nuc each treatment.
 
I have seen the you tube vids and seen much discussion on fogging.  I am the first, as far as I can tell, to ever do before and after mite counts and include controls of any type.  At this point I view all such claims as pure snake oil of the usual value that snake oil typically has but am open to being proven wrong.  I am a bit leary of firing alcohol due to flammability althou no one has reported a fire issue.  Also, oxalic acid will react very rapidly with alcohol make the ester and the ester will very rapidly decarboxylate at temps as low as 100 deg C to ethyl formate which is not going to kill mites.  If you are going to fog ethanol solutions you probably need to make fresh solution just prior to fogging to avoid the inevitable ester formation that is going to happen on storage even at room temp.  This chemistry is not a problem in water solution but needs to be considered in alcohol or particularly glycerin which some are using.
 
 Dick
 

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