The use of formic acid as a varroa treatment for honey bees has been practiced for many years, and it tends to divide opinion. I have been interested to watch Ian Steppler’s recent YouTube video content (@aCanadianBeekeepersBlog), in which he tries out Formic Pro on some of his colonies. In the end, he came to the conclusion that it does not suit his beekeeping operation, at least not in early summer. Ian is far from alone in that. For what little it’s worth, here are my thoughts on Formic Pro.

Powerful and Quick

Formic acid is a powerful and quick treatment (90%, 14 days), but there is no escaping the fact that it can be harsh on the bees (particularly open brood and some queens). However, varroa mites are one of the biggest causes of dead or dying colonies, so something must be done; there is a balance to be struck.

Beekeepers who want to keep their bees alive will generally have to work out a strategy for managing varroa mite numbers in their colonies. You have to be proactive so that things don’t get out of hand. If you find a colony with upwards of 3% infestation (9 mites from a half-cup of bees using alcohol wash) then it’s going to be very difficult to get that colony healthy and vigorous again. They are already in big trouble, and even if you kill the mites, the associated high levels of viruses remain.

Emergency Summer Treatment

The reason for me trying out formic acid pads in the past was as an ‘emergency treatment’ for colonies where the mite numbers were getting out of hand. Despite the horror stories about formic acid, and there are plenty, my reasoning was that the handful of colonies with 3%+ mite infestation in June were going to be nearly dead by August, when I normally treat, anyway. At the time, formic acid could be used with supers on, so I gave it a go. Nowadays, Formic Pro instructions clearly indicate that any honey in supers must be removed before treatment, or not used for human consumption if left on. Anyway, I lost the queens in 30% (3 from 10) of treated colonies, although these were queens from the previous season or earlier. Perhaps they were going to be superseded anyway?

I noticed that the colonies that kept their queens had beautiful new brood, and lots of it. The bees seemed much happier to me, and these colonies did very well. Considering that they were all probably gonners anyway, saving 70% was a good return. I make queens, so re-queening the others was not a problem. I did not have sneak-peaks at what was going on inside during the treatment period, but it’s fair to say that the bees hated it for the first day or two. Whatever was going on – and I’m sure it wasn’t pretty – the result was great on 70% of colonies.

Reducing the Initial ‘Flash’

Randy Oliver told me that by placing the wrapper above the Formic Pro pads (so that the tops are covered), the initial ‘flash’ is reduced, with less queen issues being the result. I know some people use a single pad, followed by another about 10 days later, but I’m more of a “blast ‘em” kind of guy. Only on strong colonies, of course. The two main advantages of Formic Pro to me are (1) it’s very quick and (2) it can kill mites that hide inside sealed brood. Covering one side of the pads to reduce the initial intensity makes a lot of sense, so I’ll be doing that next time.

Being a quick treatment is useful to me because I can get it over with in late August, which leaves ample time for re-queening and for the winter bees to be produced before things slow down in November. Incidentally, November is often the best time to carry out an oxalic acid treatment, as that’s when they are likely to have low amounts of brood.

Pros and Cons

Here are some pros of Formic Pro:

1. It is highly effective at killing varroa mites, including those within the capped brood cells, where other treatments cannot reach.
2. It breaks down naturally into water and carbon monoxide, leaving no harmful residues in the hive products (honey, wax).
3. It can be part of an integrated pest management (IPM) strategy, helping to manage mite populations without relying solely on ‘hard’ chemical treatments, like amitraz.
4. It is approved for use in organic beekeeping, appealing to beekeepers who prefer natural treatments.
5. As I said before, it’s quick (other treatments take six weeks)
   

And some cons:

1. While generally safe when used correctly, formic acid can be toxic to bees, especially the queen and young brood, if the concentration is too high or if applied improperly. It can also be hazardous to humans, requiring careful handling.
2. Its effectiveness and safety are highly dependent on temperature and humidity. High temperatures can increase toxicity to bees, while low temperatures can reduce efficacy.
3. Formic acid treatments are often limited to certain times of the year (e.g., late summer and early autumn) when temperatures are within an optimal range.
4. Adequate hive ventilation is crucial during treatment to prevent harmful buildup of fumes, which can be challenging in some hive setups (solid floors).
5. The treatment can be stressful for the colony, potentially leading to temporary disruption in hive activities and behaviour.
   

Useful Part of IPM

I am happy to have Formic Pro in my armoury, to be used as part of IPM. If I did not have mated queens to use up, I would probably be less gung-ho with formic acid. One problem I have had is that, if the queen dies during treatment, and the replacement queen is not accepted by the colony, it’s a bit of a write-off. That queen could have gone into a nucleus colony, taken through winter, and be ready to explode into productivity the following spring. I may choose to split up any strong colonies that lose their queen as a result of Formic Pro treatment, as long as I have queens available. Nucs made up late in the season seem to do well as long as they have three frames of brood, a vigorous queen, food etc.

So, the decision to use Formic Pro is not straightforward, but I’m pleased with it. It’s organic, and if I use it late season and have spare queens, I’m covered.