Oxalic acid vaporization, though not my only method for managing varroa mites, is obviously a staple treatment given the fundamentals of my online mite calculator. But there have been legal—and therefore ethical—restrictions for year-round use of oxalic acid due to labeling that prohibits its use with honey supers. But that’s changing.
In 2021, the US Department of Agriculture approved oxalic acid treatments—both vaporization and dribble methods—for application in the presence of honey supers. This takes effect on February 23, 2021, though it’s still not allowed until labels on approved oxalic acid products are ammended. That should happen soon, as the USDA is currently working on supplemental labels. Once those labels are available, it might be a good time buy a new supply of OA from a reputable beekeeping supplier.
The power supply for my oxalic acid vaporizer—a 1949 Ford 8N tractor
So how much does this affect me? Not much. My OAV schedule is built around the honey flow, so the previous labeling has never been an impediment on my operations. While I’m happy the USDA is following the science already well-understood in Europe for literally decades, I don’t anticipate needing to treat my hives when honey supers are installed. I suppose that could change, but my routine of a mid-winter treatment, an early spring treatment, and then any necessary treatments (dictated by mite loads of each hive) after supers are pulled has worked splendidly for me and my bees. The major honey flow in my area lasts maybe two to three months, and in my experience a honey bee colony that is properly prepared in the spring, and is then properly cared for in late summer and fall, can be healthy with mite loads that are quite manageable during that brief period.
A puff of oxlaic acid escapes a screened bottom board during a vaporization treatment
That being said, the label is changing, so if you’ve struggled with mites overwhelming your hives in the early summer, you’ve now got another treatment option. I’d first recommend you try the schedule I mention above to avoid treating with supers on; but the science—and the USDA—is on your side if you decide OA treatments are necessary during the honey flow. Just be sure you’ve got an oxalic acid supply with the new labeling to stay on the up-and-up.
UPDATE: Here’s the EPA’s supplemental label for Api-Bioxal, which authorizes its use with honey supers.