Formic Acid Treatment for Bees

Among many treatment options, the use of formic acid for bees is one way to battle varroa mite infestations in our hives. The constant battle to control varroa mites in beehives is a struggle for beekeepers. When these pests invade our hives, we are faced with trying to kill an insect on an insect. That’s not easy.

Formic Pro is one form of formic acid treatment to control varroa mites. I use it in my hives but not during all of the season. Is formic acid the best varroa mite treatment option for your situation? That depends on several factors including your location. 

Formic Acid Kills Mites

Unlike many of the synthetic compounds created for mite control, formic acid is a simple organic acid. This natural component is found in many foods that we eat – even honey.

It is also friendly to insects in most cases. Ants contain formic acid in their bodies. However, this natural acid, can be powerful too. Just the same as when we use vinegar as a weed killer. These materials are natural but strong.

When formic acid evaporates at warm room temperature the vapor becomes a fumigant that kills varroa mites. It is also reported to help with tracheal mite control – another honey bee pest.

As with many natural substances, the strength or concentration is very important. In this case, the trick is to have a formic acid vapor concentration that kills mites without harming the bees or other resources in the colony.

Challenges of Using this Natural Treatment

Unfortunately, there is no perfect varroa mite treatment. At least, not that I have found. Any method has a risk of resulting in some loss. Beekeepers using formic acid need to be aware of these issues.

• Temperature during treatment phase
• Some bee and/or brood loss common
• Possible queen supersedure

Summer Temperatures

Treating for mites in the middle of a hot Summer has always been challenging for us beekeepers living in the South.

The treatment instructions clearly caution against using formic acid for mite control when the daytime temps are above 85°F.

This can be an issue here in the South. That temperature range, and don’t forget to add in high humidity too, lasts from about May until September in my area. Finding a good temperature window is the issue.

However, you can-and I have, used formic acid during the Summer if you get a break in the heat with cooler temps for 3-4 days at the beginning of the treatment window.

If we are lucky enough to get a rainy weather pattern that lowers the daily highs – that is an opportunity.

Does Formic Pro Kill Bees?

The use of Formic Pro or any mite treatment can result in the loss of some bees and/or brood. The truth is that colonies infested with mites are unhealthy compared to those without mite infestations.

Treating a colony for mites causes stress on the bees. However, loosing a small number of bees that may already be weak is an acceptable risk for most beekeepers. Better to lose a few hundred and build back healthy hive numbers. 

It is common to see some brood being removed from the colony or perhaps a few more dead bees during the first days of treatment.

If you have an extremely weak colony with a low population, formic acid would not be the best choice for varroa mite control.

Some bee bearding during the first day or so is normal – but your bees should not completely leave the hive. After a few hours those clustering outside should return to the interior.

Colonies May Supersede Their Queen

Even though I have never experienced this in my hives, research shows that there is a higher percentage of problems – perhaps loss of the queen in some colonies treated with formic acid.

Of course, there are many reasons a colony may decide to make a new queen. With any mite treatment, and formic in particular – be sure to check your queen status a month after treatment.

Will Treatment Affect Honey in the Hive?

No, when used according to manufacturer recommendations, formic acid residues in honey are not raised to any appreciable level. Likewise, the beeswax comb is safe to be eaten – it is not affected with an accumulation of the acid.

As clearly outlined in the instructions from the manufacturer, there are 2 methods of using formic acid pads in the hive. One method (as demonstrated in this article) uses 2 pads per hive at the same time.

The second method is slightly different. One pad is placed on the top bars of the brood box.10 days later, that pad is removed and another added in its place.

The method of using 1 pad at a time is useful for smaller colonies (weaker) or times when the temperature treatment window may be near the limit.

However, using 1 pad at a time will not kill the mites in the capped brood cells as efficiently. Since that is where most of the mites reside, I opt for the stronger option.

Follow Up

Always read the instructions provided by the manufacturer – things change!

Formic acid is a very effective treatment option for beekeepers living in regions where temperatures allow. Be sure to check your queen status a month after treatment (which you should always do anyway).

Also, check your varroa levels a few weeks after any treatment. You can not assume it worked – too many variables.

Another soft treatment –oxalic acid kills mites in beehives. Vaporization with OA is my primary mite control method, there are times when other products are effective. I generally use formic acid in my hives in the Fall when the temperatures moderate.