Safe Varroa Treatment

thanks to Smart Dispenser

Varroa destructor – the name says it all. This little mite is the most dangerous threat to the Western Honey Bee. Years ago, beekeepers in Germany, Austria and Switzerland discovered formic acid as a varroacide, an effective substance to control the Varroa mite via evaporation of the acid in a beehive. However, its application is tricky – not just from an operator safety and bee health perspective but particularly because in the evaporation systems used today, the acid’s efficacy in the beehive is highly dependent on the daytime outside temperature. Formipenser® aims to solve these application problems and supply the beekeeping community with an effective tool to control Varroa.

Safe <em>Varroa</em> Treatment


// In the search for an effective means of controlling the Varroa destructor threat to Western Honey Bees and the growing resistance problems with synthetic varroacides, beekeepers in Central Europe discovered formic acid as a resistance-free solution.

// As formic acid is, however, difficult to handle and successfully dispense in beehives, the Formipenser® project was initiated to tackle these issues.

// Formipenser® utilizes the constant 35 °C temperature kept up by the bees in beehives and a smart dispenser design to ensure effective, controlled evaporation of the formic acid.

// The results from initial field trials in temperate climate zones have been very encouraging and additional field trials are established, especially in hotter climates, like Spain.

Research to control Varroa

The Formipenser® membrane element which dispenses the formic acid can be placed on top of the frames in a beehive, as seen here ...

Finding an effective means of controlling the Varroa mite is a top priority for beekeepers, particularly across European and North American regions, where the Western Honey Bee occurs. Many of the synthetic varroacides developed in recent decades now face resistance issues due to overuse and a lack of alternatives featuring different modes of action. Spain for example, an important honey-producing country, has no resistance-free, synthetic varroacide left on the market. And, there are no new pest-management products in the pipeline to replace the older chemistries. With registration of new varroacides taking around a decade, and regulatory hurdles for the registration of veterinary products being high, the prospects for new chemistries being brought to market any time soon are far from rosy. This is one of the reasons why beekeepers in Central Europe are using formic acid on a regular basis today.

... or between the frames, next to the honeycombs, as seen here. Further tests will show, which placement is more effective for the evaporation of formic acid.

This naturally-occurring, organic acid is produced by most ant species as a defense secretion and also kills mites such as Varroa destructor. To date, no resistance issues have been reported by beekeepers using formic acid. Unfortunately, it is far from easy to handle and special protection is needed as contact with the skin or eyes causes irritation or physical harm. Moreover, as formic acid needs to be evaporated to be effective against Varroa, the outside temperature plays a critical role in successful evaporation of the acid in a beehive. Daytime temperatures of 20-25 °C, over a 3-5 day period are required: if the air is too cold, evaporation of the acid is impaired; at temperatures above 30 °C the acid may evaporate too quickly, creating a concentration in the hive which may prove fatal to the queen bee and brood. Up to now, this has precluded the use of formic acid application during the late summer and autumn period in beekeeping countries such as Canada or Spain, as the given temperature in these regions is very often out of the recommended temperature range. The Formipenser® project involving Professor Wolfgang Kirchner from Bochum University, Helge Adleff from WaldWieseHolz GmbH and the Bayer Bee Care Center, all in Germany, was initiated to solve this temperature-related dispensing problem and extend the efficacy of this Varroa-control tool beyond temperate climate zones.

A Varroa mite, on a honey bee, can transmit deadly diseases.

The aim of the project is to develop a dispenser that enables convenient application of formic acid for effective Varroa control in beehives – irrespective of the outside temperature – while being safe for honey bees and beekeepers, alike. What Helge Adleff and Professor Wolfgang Kirchner have designed, with Bayer’s support, is a simple and smart solution that makes use of an interesting constant: Whatever the outside temperature, bees maintain a breeding temperature of 35 °C in a beehive. “This is one legacy of the honey bee’s tropical heritage,” Professor Kirchner points out. Formipenser® makes intelligent use of the natural conditions and constant temperature in a beehive to reliably evaporate formic acid via a membrane, placed close to the brood. The size of the membranes in this dispenser is another critical efficacy-related factor. The project participants used their expertise and experience to come up with what they believed was the optimum membrane size to deliver the desired concentration of formic acid. So far, so good – but would the dispenser work in practice?

The experts involved in the Formipenser® project (l-r): Helge Adleff from WaldWieseHolz GmbH; Peter Trodtfeld from the Bayer Bee Care Center; Volkmar Krieg, field-trial manager and beekeeper at the Bayer trial station Höfchen, and Professor Wolfgang Kirchner from Bochum University.

Helge Adleff adjusts the flow of formic acid into the membrane dispenser.

The first field trials took place at Bochum University and the results were significantly better than those achieved by the standard formic acid dispenser. After tweaking several parameters, further trials were run in 2017 at Bochum University and Bayer’s Höfchen trial station in Germany, again with encouraging results. Helge Adleff was upbeat: “Our goal is to develop a plugand- play dispenser so beekeepers no longer have the tricky task of transferring this acid from large storage canisters into small, individual containers for each hive, as with the dispensers currently on the market. We want to minimize the risk of formic acid spilling on the skin. All the beekeepers have to do with our dispenser is unpack it and place it in the hive near the brood. They may even forget it’s there – until they see the dead mites”. In filing a patent application for Formipenser®, the prospects for a globally-applicable formic acid dispenser are looking brighter than ever.

Formic Acid

Formic acid (CH2O2), also known as methanoic acid, is a naturally-occuring organic acid used as a defense mechanism by most ants, stingless bees of the Oxytrigona genus and in the trichomes of stinging nettles. Wood ants spray formic acid on their prey or use it to defend their nest, and the name is derived from the Latin word for ant, formica. A colorless liquid with a pungent, penetrating odor at room temperature, formic acid is put to a wide variety of uses, e.g. as a preservative and antibacterial agent in livestock feed, in tanning leather, in dyeing and finishing textiles and by beekeepers as a means of controlling the tracheal and Varroa destructor mites in honey bee hives. To meet the global demand for formic acid, it is produced synthetically in Europe (mainly Germany) and Asia (mainly China). Although formic acid has a low toxicity to humans, in concentrated form it is corrosive to the skin and can damage the optic nerve. Hence special care and protective clothing are needed during handling.

Outlook ////

The field trials established at the University of Cordoba in Spain are expected to deliver new findings about the ideal membrane size and positioning in hotter climates. Depending on the results of these and other field trials at Bochum University and Höfchen, Peter Trodtfeld, the project coordinator at the Bayer Bee Care Center, hopes that field trials under registration-relevant conditions can be carried out in 2019. The project is scheduled to run till 2020 and all those involved are optimistic that an effective and resistance-free solution to the Varroa destructor problem will be available to the global beekeeping community in the near future.


The Formipenser® may be a good solution for countries with an extreme climate in late summer and autumn, like Spain or Canada, due to the fact that it works inside the hive, next to the brood, where there is a constant temperature of 35 °C, irrespective of the outside temperature.

Nettle stings contain formic acid as well as, among other chemicals, histamine which causes the initial inflammation, swelling and redness when you are stung.

Varroa destructor is one of the honey bee’s worst enemies.

Using temperature to protect honey bees

Professor Wolfgang Kirchner is an expert in applied entomology from the Faculty of Biology and Biotechnology at Bochum University, Germany. One of his fields of research is the biology of honey bees and how they combat parasites, in particular the Varroa destructor mite.

Why is formic acid used to protect honey bees from the Varroa destructor mite?

Kirchner: When these mites first appeared in Europe in the 1970s, synthetic varroacides were used to combat them. But when resistance to these products became apparent and varroacide residues were found in honey, scientists began searching for naturally-available varroacides. They discovered, more or less by chance, that certain organic acids, including formic acid, had a toxic effect on these mites. Formic acid was then registered as an active substance and has proven to be very successful as a varroacide. No resistance issues have emerged so far and there have been virtually no residue problems in the honey.

So formic acid has been an unmitigated success story?

Kirchner: Not quite. Successfully dispensing the right concentration of formic acid in a beehive is dependent on several external factors, in particular the outside temperature. If it’s too cold, the acid doesn’t evaporate. If it is too hot, it evaporates too fast and may harm the bees. The difficulty with formic acid is that there is only a very narrow margin of error between the desired effect, i.e. killing the mites, and a harmful impact on honey bees, particularly the queen bee. Although formic acid is classified as a weak acid, it’s actually a rather strong one and an unpleasant skin irritant, so its application is rather tricky. The solutions developed up to now for dispensing formic acid have several disadvantages, so our aim was to come up with a practical solution that is easier and safer for beekeepers to use.

“This innovative dispenser makes intelligent use of the constanttemperature conditions that exist in the brood nest.”

Professor Wolfgang Kirchner from the Faculty of Biology and Biotechnology at Bochum University, Germany

How did you arrive at your solution?

Kirchner: Together with my research team, I had been involved in two previous attempts to develop a better dispensing solution but though both were effective, neither were practical. Helge Adleff wanted to use his expertise to help control Varroa mites. When he contacted me, I was keen to start working with him. Our idea was to use the constant temperature of around 35 °C that honey bees maintain in the brood nest for dispensing the formic acid in a carefully controlled manner.

The first pre-trials were conducted at Bochum University. How did they go?

Kirchner: We were delighted that our dispenser worked so well at the first attempt! In 2017, we made some slight improvements and the results were again very encouraging.

What are the next steps?

Kirchner: So far, our field trials have taken place in Germany, with its relatively moderate summer temperatures. Now we are starting to test our dispenser in countries with higher summer and autumn temperatures, e.g. in Spain. The other issue we’re tackling is that beehives come in all shapes and sizes so we need to produce one or two dispenser models that are suitable for the majority of hives. Therefore, we are currently having prototypes produced using a 3D printer.

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Safe Varroa Treatment thanks to Smart Dispenser
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