The vaporizor that I build worked good aerlt this spring, did not hurt may bees. I did not say no effect, but there are are plenty of studies that shows that OA to be very effective killing mites, with little little harm to the bees.
Radetzki didn’t note increased bee mortality after winter treatment. Heinz Kaemmerer of Heilyser Technology Ltd. says: “We treated several colonies for 3 months during winter, once a week with the vaporizer and all colonies survived.” “With brood, colonies can be treated with the right amount of OA 3 to 4 times, a week apart; there is no harm to bees, queen or brood.” Medhat Nasr confirms that vaporized oxalic is very gentle to the bees.
Marinelli E., Formato G., Vari G., De Pace F.M. 2006 VARROA CONTROL USING CELLULOSE
STRIPS SOAKED IN OXALIC ACID WATER SOLUTION Apiacta Vol 2006
Radetzki, Thomas. Vaporization of oxalic acid and working safety.
Radetzki, Thomas. Vaporisation of oxalic acid in a field trial with 1’509 colonies.
Rademacher and Harz (2006) Effectiveness of Oxalic Acid for Controlling the Varroa Mite. ABJ