The new pandemic has us emulating our bees in this time of year, huddling at home except to occasionally forage in a lacuna-ridden foodscape and largely living on what we had stored. We generally try to keep pantry and freezer rather full and, thanks to the perspicacity of the Mrs, had gently augmented our stores over a few weeks before the panic-buying locusts struck. Thus far we are healthy and fed and hope to continue in that state. We wish the same for our readership. Meanwhile, let us write about the old, familiar pandemic which plagues our bees, varroa.

We have found the autumnal oxalic treatment against varroa to be critical in our hives surviving the winter. Unfortunately an oxalic drip/drench is annoying because bars need to be separated and we must juggle syringe and container of treatment solution.

Vaporizers may be faster and can be used when one does not wish to risk wetting bees but the commercial ones do not fit our entrance holes. We considered trying to homebrew something but out typical overdesign process quickly ran aground.

A more determined local beekeeper in charge of a few Kenyan-style top bar hives modified their end entrances to accept a commercial vaporizer wand. Alas, the treatment proved ineffective because the vapor did not drift the length of the hive. In a vertical hive it would rise up at least enough to cover the brood nest.

That leaves a third, recent alternative of foggers, which have thin nozzles. Rather than trying to sublimate solid oxalic acid they use a fine vapor of oxalic acid solution. In a horizontal hive one would expect the same problem of insufficient vapor drift from an entrance, but if spraying into each of many entrances along the side, there is hope. While some beekeepers repurpose the insect foggers available from yard and garden centers, last October we opted to try one made specifically for beekeeping, the Varomorus fogger.
Unsurprisingly a propane tank is not included. And while a breathing mask is part of the kit, we opted to get more substantial masks.

We have seen videos of people using the apparatus without protective gear but that strikes us as foolhardy.

It does look somewhat awkward but is easy to use. The pistol trigger is just the igniter for the propane while the control to feed liquid is another lever under the solution tank. We found it simple to use one hand to hold it by the propane tank and the other to pump the lever.

The company has already re-engineered the solution tank attachment for easier assembly than earlier models allowed so there is hope that the form factor of later models may improve. Their customer service is very responsive.

We were concerned about spreading hot vapor into the hive but, as the thermal image of us firing the fogger outside shows, the fine vapor quickly cools to ambient temperature. Even the hand, seen at left of image, holding the apparatus is warmer.

The instructions that come with the device specify using ethanol as the solvent for the oxalic. We were timorously intending to use water instead but, after seeing so many others around the web specify ethanol, compromised on hundred-proof vodka. Presumably the ethanol is faster than water in evaporating and cooling the spray but we could not convince ourselves that spraying a flammable, vaporized liquid into a wooden structure would end well.

We had already corked all but one entrance of each hive as the weather turned colder. Now after one of us sprayed a few bursts at various angles into the remaining entrance hole, the other corked the entrance. Then uncork the next hole and repeat down the length of the occupied part of the hive. After all holes were corked, we waited a minute or so and then uncorked the single winter entrance. Then we subjected the next hive to the procedure.

This all took very little time at all. An electric vaporizer would require a cooldown and warmup period between applications. And the propane tank fuels many more applications than the usual car battery, unless one can bring the entire car to the hives. The varomorus is much more portable.

Then we stood there watching the hives. As with previous oxalic treatments the bees did not seem at all inclined to attack but there was a slow stream of bees leaving the hives and dropping to the ground, where they would crawl about. While we wondered aghast whether it was heat, acid, or alcohol that had injured them, the stream slowed and stopped after a score or so of bees. We scooped up half a dozen into a small jar with screened top and took them indoors. The next morning one of the six seemed perfectly fine. One weakly moving. The rest seemed dead. Perhaps we had been overenthusiastic in our spraying. Peeking through the observation windows showed bees at work as usual. Not the carnage we had feared.

Now in late March we have seen clouds of bees flying from both hives on the warm days. So far, so good but proper springtime, not that equinox pretender, is yet to come.