Formic Acid Treatment for Honey Bees

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Controlling parasites is standard part of beehive management. One such parasite of honey bees is the Varroa mite, which can causes colonies to get weak and deformities to appear in bees. Various treatments are applied by beekeepers to keep Varroa mites in check. Formic acid is one such treatment used and it can be applied in various forms. You can make your own formic acid preparations for the various methods of application. However, there are also some formic acid treatments for honey bees solutions that are sold to beekeepers. They are easy to use and can be applied by both beginner and experienced beekeepers.

What is Formic Acid?

Formic Acid Treatment for Honey Bees

Formic acid is a colorless liquid that fumes. It has a pungent penetrating smell. The acid is miscible in water and other common solvents while being partially soluble in others. In high concentration, the acid can be corrosive and very irritating. In nature, some insects produce formic acid. It is also a component of the atmosphere that occurs naturally. It has many uses by humans, including as a miticide. Beekeepers use formic acid to control Varroa mites and tracheal mites. Formic acid in normal use has low toxicity and is even used as a food additive.

In beekeeping, formic acid can be bought in high concentration preparations. Dilution is done before application using various methods. Preparations sold to most consumers are of diluted formic acid. There are both slow-release and rapid-release methods of introducing formic acid into beehives for Varroa mite control. They include vaporization, using evaporators and use of strips. A 60% solution of formic acid is used in vaporization and fogging. Lower concentrations are used in formic acid slow-release strips. The strips employ an absorbent material dipped in a solution of formic acid.

How Formic Acid Works

Over the years, formic acid has distinguished itself as one of the most effective treatments against Varroa mites. It kills the mites with ease and the mites cannot develop resistance to the effects of the acid. Various aspects of Varroa mite control using formic acid have been investigated by researchers. Many beekeepers, across many countries, have been involved in the research. They allow researchers to access their bees, beehives and share relevant beekeeping information with the researchers. The results of such experiments and research have gradually changed the way formic acid is prepared and applied in beehives. Developments in the use of formic acid in beekeeping have also given beekeepers preparations that have extended shelf life.

In comparison to most other Varroa mite treatments, formic acid has high efficacy. It starts killing mites gradually and achieves a peak about 3 days after the onset of application. After that, formic acid treatment gives a steady rate of mite fall for the rest of the treatment period. The mites keep dying until none are left in the beehive. For best results and to avoid repeat treatments soon after the first treatment, a complete bee brood cycle of 16 days is allowed to lapse during treatment. The treatment kills mites that are moving in the beehive, some mites under cappings and mites released into the beehive upon brood emergence from capped cells.

Ensuring Effective Formic Acid Treatment for Honey Bees

Effective treatment for Varroa mites is needed for various reasons. It slows down spread of the mite infestation in the apiary and helps relieve stress on the honey bee colony. Treatment with formic acid also kills tracheal mites in bees. It allows subsequent generations of honey bees in a colony to be strong and healthy. Without effective treatment, Varroa mites can quickly overrun beehives and cause massive losses in your beekeeping operation. With some methods of application such as fogging and using strips, repeat treatments are needed for best results. The duration of treatments and the time that should lapse before repeat treatments are applied, vary by method of application.

Vaporizer or Fogger

Vaporization with formic acid is done using a vaporizer. The acid is heated to a high temperature and the fumes are released into the beehive. Vaporizers often run on 12V power. Most beekeepers with vaporizers use car batteries to power them. They are very effective in application of treatments and allow you to treat many beehives in a day. Foggers too can be used to apply formic acid for Varroa mite treatment. The openings through which some of the vapors or fog could escape may need plugging shut for some time after treatment. Later, the beehive would need to be ventilated.

Vaporization and fogging spreads vapors of the acid into the beehive. The vapors cool and attaches onto beehive surfaces. Bees that come into contact with the formic acid, spread it to other areas of the beehive. Mites on the backs of honey bees also come into contact with the formic acid. It begins acting on them immediately. In a few days after treatment with a formic acid preparation of any type, you will note mites dying and falling. The final results are known at least 16 or more days after treatment is started. This is because it takes about 16 days for the brood cycle to end. The mites emerging from capped brood are usually dead when formic acid is used, or die soon after emerging.


Evaporators for formic acid treatments vary in design and efficiency. The best evaporators hold a sizeable amount of the acid. They have wicks that help with slow release of formic acid into the beehive. A gel matrix may be mixed with the formic acid in an evaporator to improve safety when handling the acid. Evaporators rely on high ambient temperatures for successful release of the formic acid into the beehive. In very cold temperatures, the evaporator may fail or release very little amounts of formic acid. The treatment is ineffective and mites may persist in the beehive. Evaporators are also not very popular because of their potential to release too much of the formic acid into the beehive when ambient temperatures get too high.


Applying formic acid via strips soaked in a preparation of the acid is another method that beekeepers use. It releases a little of the acid at a time into the beehive. The strips rely on contact with honey bees for spread of the acid throughout the beehive. They are usually placed on the tops of beehive frames. Some of the acid finds its way into various parts of the beehive in this manner. It kills mites attached to honey bees and those moving about in the beehive. When applied properly, it can also kill mites that are under cappings. Repeat treatments kill any of the mites that did not die under cappings and have been released into the beehive after the first treatment.

Formic Pro Strips

Formic Acid Treatment for Honey Bees - NOD FormicPro 30 Doses (60 Strips)

One of the popular strip application preparations of formic acid is Formic Pro™. It is a mite treatment solution made in Canada and sold by NOD Global. Available packs of the product include a 2-dose package, a 10-dose package and a 30-dose package. The packages are suitable for various beekeeping operations based on the number of beehives to be treated, and the treatment regime that will be used in each beehive. A number of retailers and beekeeping supplies sellers stock Formic Pro. They sell the mite treatment both online and offline.

  • The smaller packs are great for small beekeeping operations. They allow you to treat your beehives and have a few strips left for repeat treatments. It is possible to use up all the strips before they expire.
  • The larger pack is excellent choice for large beekeeping operations. It gives you many strips to use in your numerous beehives. Strips that are not used are stored and used in subsequent treatments.
  • If Formic Pro strips are expired, they should be disposed of carefully. The expired strips should not be used in a beehive.

Temperature and Formic Acid

Temperature plays a big role in the effectiveness of formic acid treatment for honey bees. At very low temperatures, the acid does not spread out with ease into the beehive. At high temperatures however, the acid breaks into carbon dioxide and water. You should therefore make sure temperature ranges are right when using formic acid treatment.

  • In winter, heating beehives can help improve circulation of the treatment. It is necessary when you notice a mite infestation during winter that threatens to harm the honey bee colony.
  • When heated, the winter cluster breaks and honey bees move around in the beehive. They also tend to consume more of the stored honey. The number of brood might also rise.
  • You should be ready for these changes when heating the beehive during winter and only treat for Varroa mites using formic acid if it is very necessary to do so.

Safety Precautions When Using Formic Acid

It is important that you take enough safety precautions when handling formic acid. Despite its concentration, make sure to at least wear gloves when handling the acid. Other safety measures such as a gas mask and corrosion-resistant goggles might also be needed depending on the concentration of the formic acid. The acid can be injurious due to prolonged exposure too. After applying the acid, wash the hands as an additional safety measure. It is good to have water nearby when working with formic acid. Take care to not inhale fumes of the acid. In the event that some acid gets into the eyes or on your skin, the water is used to wash off the acid. You should also try to be always upwind of the acid and be cautious when opening containers of formic acid.

Beekeepers using concentrated formic acid preparations might spill some during use or when diluting the acid to use it in their beehives. In the event of a spill, wash the acid off using a lot of water. If the spill is onto soil, drench the ground around the spill with large amounts of water. Different surfaces react differently to interaction with formic acid. For most cases, washing the acid off the surface immediately prevents the worst damage from happening.

Coveralls should be worn when working with formic acid. To protect the hands, a long sleeved shirt should be worn under the coveralls. Socks and shoes also form part of the safety wear you should use with formic acid. A trouser or long pants worn under the coveralls give the legs additional protection. All clothing worn during interaction with formic acid should be cleaned and replaced at the end of each day. Hot water and detergent are required for cleaning such clothes. The clothing should be separated from your other laundry.

Storage of Formic Acid

Storing formic acid is advised to be done in a plastic container. The acid is kept indoors away from direct sunlight. The storage room should be cool, well ventilated and dry. Other acids such as sulphuric acid should not be near formic acid. Additionally, oxidizing agents and ignition sources should not be allowed near the stored formic acid. You should make sure children cannot reach the stored formic acid. The storage area for formic acid should not be use for drinking, eating or smoking activities. Cross contamination of fertilizers, other pesticides, feed and food should be avoided. Formic acid preparations often have a long shelf life of up to 2 years. Cool temperatures help keep the preparation fresh throughout its life. Freezing is however not recommended.

When to Use Formic Pro

Formic Pro is a hive fumigant that can effectively get through brood caps. Up to 80% of Varroa mites in a hive are found in developing brood. They are killed when Formic Pro strips are used near the brood rearing area of the beehive. For this reason, it is not uncommon finding beekeepers placing Formic Pro strips on top of the frames of deep brood boxes. The strips are placed across frames, not alongside them.

The best time to treat for Varroa mites using Formic Pro is in late spring and mid fall. In late spring, treatment ensures the honeybee colony is strong going into honey flow. It produces high amounts of honey in the season. Mid-fall treatment for Varroa mites focuses on ridding the hive of Varroa mites just before winter and keeping the wintering colony free of mites. With mid-fall treatment, the mite population is kept low through winter so that the colony emerges strong in spring.

Formic Pro Instructions

To use Formic Pro, open the sachet and remove the strips. Separate the strips so that each strip is used independently. Formic Pro strips come attached to some eco-paper wrap that wicks formic acid and releases it slowly as a vapor into the beehive. The biodegradable wicking eco-paper wrap should not be removed from individual Formic Pro strips.

Treatment using Formic Pro strips can follow two regimes. One is to use 2 strips in a beehive and leave them in place for 14 days. The other option is to place one strip in the beehive for 10 days, and then a second strip for a further 10 days. When using 2 strips at the same time, place them some distance from the ends of the beehive boxes, and with a gap of at least 2 inches between the individual strips. A month should lapse before a repeat treatment with Formic Pro strips. The treatment should not be mixed with other miticides.

Ambient temperatures are a major consideration when treating with Formic Pro strips. The daytime temperature should be between 50-850 F (10-290 C) during application. The vapors of formic acid are released well during the warm day and fanned to the rest of the beehive by bees. Clustered bees do not fan the beehive and thus the efficacy of formic acid treatment is not realized. Temperatures higher than those in the given range lead to high concentration of formic acid vapors. This can result in bee and brood loss. In the worst cases, the queen bee can die and require you to requeen the beehive.

In the event that formic acid comes into contact with your clothing, skin or eyes, remove the contaminated clothing and rinse the area well with clean water. Washing with a lot of clean water applies to the eyes too and the skin. After washing, visit the doctor for further medical assistance. If formic acid is swallowed, do not induce vomiting.

Does Formic Acid Kill Honey Bees?

Formic Acid Treatment for Honey Bees

Formic acid can only kill bees if it reaches high concentrations in the beehive. The concentration of formic acid that is lethal to mites is low. As such, bees are not affected by properly applied formic acid to control Varroa and tracheal mites. Once treatment with formic acid has ended in the beehive, the acid dissipates very quickly. In a few days, it is back to very low concentration. Beehive products can be harvested from a beehive that was treated with formic acid a few weeks after the end of treatment.

Bee bearding might be observed for a few days after treatment with formic acid is done. They are more likely to beard out when temperatures are warm. The bees cluster around the entrance of the beehive and the bottom board if it is screened. To prevent bearding out, add space to the beehive by placing an extra beehive box on the beehive stack. It gives bees some space into which they move to get away from the strips of Formic Pro.

Disturbing the beehive during treatment should be avoided. This also applies to disturbances to the beehive just before application of formic acid. The acid can cause absconding to happen if bees are disturbed too much during application. Allow up to a day to lapse between opening up the beehive and starting formic acid treatment.

Once started, allow at least 3 days from the start of treatment to the first opening of the beehive. At this time, you can inspect the beehive and honey bee colony to find out if there is a queen bee present some time after treatment. You could also check for signs of the presence of a queen bee such as freshly laid eggs in honeycomb. The continuous presence of both capped and uncapped brood is also an indicator that the honey bee colony is queen-right. Furthermore, you can feed bees during and after treatment with formic acid preparations. External feeding does not disrupt the beehive and ensures the bees are well nourished.

A Final Word

Varroa mites transmit harmful viruses in honey bee colonies. They have increased in prevalence and spread over the years. The mites easily cause honey bee colonies to die off in heavy infestations. Treating beehives for Varroa mites reduces the number of mites in the beehive. When used well, it can rid the beehive of the mites. Formic acid is a reliable killer of Varroa mites. The best formic acid treatment for honey bees is applied at the proper concentration to be harmful to mites but safe for bees. It is one of the safer treatments to apply, even when there is a crop of honey in the beehive.

Beekeepers use a combination of methods and treatments to control Varroa mites. The use of formic acid can be incorporated into your general beehive management practices. It can also be part of your integrated pest management in the beekeeping operation. Repeated treatments of formic acid can be carried out in a beehive. While it is not very advisable, Varroa mites do not develop resistance to the acid. This is unlike some other treatments for Varroa mites used by beekeepers. The mites develop resistance to some of the treatments. Beekeepers should make sure to apply all beehive treatments well and in the right concentrations to prevent parasites of honeybees from developing resistance to treatments.

Do you use formic acid treatment for honey bees? Leave a comment below and let us know what were experiences were like.

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6 months ago

what the amount of formic i must vaporize for one hive>>

6 months ago
Reply to  BeeKeepClub

is the vaporizer like the oxalic one .what the amount we must use?
could you please show photo or video for formic vaporizer.
your website is very good and useful one .best regards

6 months ago
Reply to  BeeKeepClub

sorry. I mean can we use the oxalic fogger for formic. and what the amount of formic we must fogg for one hive please
best regards

6 months ago
Reply to  BeeKeepClub

sorry .I mean fogger

6 months ago
Reply to  BeeKeepClub

Is the formic acid evaporator the same as we use in the vaporization of oxalic acid?
I am using 100 ml of ethyl alcohol with 25 g oxalic acid (as you explained in your articles). Should I mix the formic in the same amounts?

6 months ago
Reply to  BeeKeepClub

thank you very much I will apply it
best regards

Vincent Clark Sr.
Vincent Clark Sr.
6 months ago

[spoiler title=” “]I would like to know about oxalic acid and glycerin mixture and treatment

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