Bringing new bee health varroacide products to market

Developing new treatments

As the threat of Varroa continues, scientists are keeping up their search for effective ways to help beekeepers protect their colonies from this destructive pest. But developing new treatments isn’t easy.

Bringing new bee health varroacide products to market


// Even though the parasite, Varroa destructor, is widely regarded as the single greatest threat to honey bee health, new tailored pest management solutions to replace long-standing older chemistries have not entered the market and are not foreseen in the near future.

// Registration of a new varroacide is similar to that of any new pesticide, which can involve more than a hundred basic studies and an average of eleven years to take it from concept to commercialization.

// Bayer scientists are working collaboratively in private / public partnerships to amplify the search for new Varroa solutions. 

Rhipicephalus male

Acaricides are chemical agents to combat mites and ticks. The picture shows a male brown dog tick (Rhipicephalus sanguineus).

Only a few years separate the invasion of the Varroa mite in Europe and its spread to North America. Beekeepers in both continents have suffered equally the losses of honey bee colonies caused by this destructive pest. In the 30 years since its introduction, the Varroa mite (Varroa destructor) has quickly become the most dangerous pest of honey bees, earning the label “Public Enemy Number 1” from US beekeepers. Worldwide, this pest is estimated to have killed millions of colonies, resulting in billions of dollars [euros] of economic loss.

Unlike the Asian honey bee (Apis cerana), the original host of Varroa mite, the Western honey bee (Apis mellifera) which is prevalent in Europe and North America has few natural defenses against this invasive parasite, which affects bees by direct feeding and by vectoring infectious viral diseases. It only takes a few mites per hundred bees to severely weaken a hive. Without prompt human intervention these infestations can cause major colony losses. Many successful beekeepers use an integrated pest management (IPM) approach in dealing with Varroa. This involves rigorous monitoring of hives to assess the problem, use of apicultural practices to determite population build-up, and the application of chemical varroacides to reduce mites, or prevent re-infestation.

Varroa mites

Substances specially developed to combat the Varroa mite are called varroacides. The picture shows mites at various development stages in a brood cell of a bee colony.

Until such time as the Western honey bee develops a natural tolerance to Varroa, or new Varroa-resistant strains are commercially available, the use of chemical control will remain a critically important component of beekeeping IPM. And yet despite the obvious need for effective varroacides, there are no guarantees that enough new treatments will be available to help address this existential threat. To better understand the situation, it is helpful to first look back from where we’ve come.

Beekeepers have always dealt with numerous pests and predators in managing their hives, but it is no understatement to say that everything changed after the introduction of Varroa. Finding appropriate chemical treatments to help them manage this new pest is no easy matter. Perhaps no one understands this better than Dr Klemens Krieger, Head of Special Projects/Bee Health at Bayer’s Animal Health Business Unit. “At the time of the Varroa introduction there were no readily available treatments,” he explains. “Today, even after 30 years of intense research effort, only four synthetic varroacide active ingredients are approved for Varroa control, two of which were developed by Bayer.”

Given the magnitude of the threat, it is easy to wonder why more treatments are not readily available. Fact is, there are several reasons why finding and developing an appropriate chemical candidate to fight Varroa is anything but easy.


The inherent difficulty of controlling a “bug on a bug” (without harming the host species) is a biological challenge that requires a level of chemical specificity that is hard to find. For example, many products that are used to control insect pests of agriculture also have some acaricidal activity. Similarly, it is not uncommon that acaricides used for mite control in crops have some level of activity on insects, too. Scientists searching for an effective Varroa treatment must find the narrow “sweet spot” that provides reliable control of the parasitic mite without causing harm to its honey bee host.

Peter Trodtfeld

Scientists who screen new molecules for apicultural uses know that there is more to this process than just finding a chemical that controls the mite without harming the bee. Dick Rogers, Principal Scientist and Entomologist of Bee Health and Integrated Apiculture Research at the Bayer Bee Care Center in the USA, is a longtime beekeeper who evaluates potential new candidates. “The difficulty in finding a bee-friendly varroacide is compounded by the fact that we’re looking for one that has a different mode of action than the currently registered products,” he notes. “Effective IPM programs require a rotation of chemical modes of action to minimize the potential for pest resistance.”

Identifying a biologically acceptable Varroa chemical candidate is a huge step, but it’s only the first of many in a complex and multilayered path to the marketplace. Establishing proof of efficacy is just one part of the registration process. A potential candidate must meet stringent safety parameters to show it will not have adverse effects on people, wildlife or the environment. Registering a new varroacide is similar to that of any new pesticide, which typically involves more than a hundred basic studies and an average of eleven years to take it from concept to commercialization.


Facts & Figures

Through the use of bee products from Bayer to combat Varroa mite in the USA for nine years, economic losses amounting to some 1.5 billion* US Dollar were prevented.

* after launch 1999 – 2007
Source: Michigan State University, 2009

The average number of veterinary medicines authorized per EU member state: bees: 3 pigs: 426 dogs: 592 The subsequent uneven distribution among the EU Member States results in little or no choice for beekeepers in some countries.

EU co-financing for beekeeping: 33,100,000 € / year

Source: European Commission fast facts, 2014


Dr Klemens Krieger works in Bayer’s Animal Health Business Unit and has long experience in developing varroacides to protect honey bees from the Varroa mite.

Not only is this path long and arduous, it is also expensive. The cost of developing a new varroacide can easily reach 100 million Euros (without including the substantial investment in a manufacturing facility). New medicinal products, developed for use in food-producing animals like honey bees, require a costly infrastructure to evaluate their molecular, biological, and toxicological properties and clinical assays to ensure their efficacy and safety when used. Additional costs involved in developing stable formulations, evaluating metabolic pathways, and field performance trials only add to this investment.

“Because it is associated with honey consumption, additional scrutiny and risk assessment is required of a new varroacide used in honey bee hives,” notes Stu Nibbelink, Project Manager at Bayer’s Animal Health Business Unit. In smaller markets such as products for commercial beekeeping, the decision to develop a stand-alone varroacide can be a significant financial hurdle because the return on investment is relatively low. As Nibbelink explains: “The most cost-efficient path to development is to find a product that has a broader pest potential to complement its use in hive pest management practices.”

There’s no question that a long and costly registration timeline is an impediment to finding new varroacides.

Currently there are few, if any, incentives in place to help expedite these ‘minor use’ products through the registration process. Despite the urgent need for new solutions, the regulatory requirements needed to satisfy a new data safety package have only continued to increase.



From idea to market maturity
Development of a new varroacide

Costs: up to 100 Mio. € (excluding cost for production facilities)



The most important requirements for an effective varroacide



  • Highly effective on Varroa mite
  • Highly selective (effect on mites versus bees)
  • Low risk of resistance
  • Good formulation properties
  • Nice to have: control of other pests such as tracheal mite, small hive beetle, hive moth, while the honey is still in the hive

Human safety

  • Low acute toxicity
  • No oncology or reproduction classification
  • Low / no residues in honey
  • Safe packing
  • Easy to use

Environmental compatibility

  • No harmful effects on bees and brood
  • No residue build-up in wax
  • No disposal issues

Profitability considerations

  • Favorable cost-benefit-ratio for the beekeeper

While the search for new modes of action continues, scientists are doing all they can to make the best use of the tools they have available – in some ways almost reinventing them to meet the challenges of today’s hive management practices. Dick Rogers is pouring through Bayer’s vast chemical archives to see if candidates evaluated for crop protection uses might have acaricidal properties that were previously unnoticed. “It’s not just about finding the right chemical, it’s also about finding the right delivery system for the chemical,” he notes. “Contact activity or volatility is greatly affected by the solvents or formulations used and can make a huge difference when evaluating varroacide products.”

Mark Drewes Bayer

Mark Drewes manages the substance library at Bayer in Monheim (Germany). Around 2.5 million substances identified in our research efforts are stored there.


Testing the contact effect of the polymer matrix with active substance during the development of the Varroa Gate.


When it comes to new delivery systems, Bayer’s Animal Health Business Unit is exploring cuttingedge innovations to help bring relief to the world’s beekeepers. For the past few years, Dr Krieger has led the development of a new concept known as the “Varroa Gate,” a plastic strip impregnated with a varroacide and affixed to the entrance of the hive. Honey bees entering or leaving the colony receive a tiny dose of chemical which they distribute in the hive. It is sufficient to control the mite population but harmless to the bee.

“One of the biggest problems beekeepers face is the mite’s ability to spread between colonies, as foraging workers return to the hive after having picked up this parasite,” Dr Krieger explains. “The Varroa Gate technology provides a novel way of minimizing re-infestations, which is especially important for vulnerable colonies preparing for the winter season.” The performance of the Varroa Gate has been evaluated in one of the largest and most comprehensive field efficacy trials of its kind ever conducted in Bayer’s Animal Health Business Unit. Registrations have been submitted in 24 countries in Europe with the intention to launch the product in the summer of 2017.

Having access to a new technology to help manage the Varroa mite is certainly a rare occurrence. But for beekeepers who have struggled with this destructive pest over the past 30 years, it is also one that cannot come soon enough.


Hanging a Varroa mite control strip between the combs in a beehive is one of the methods used to apply a varroacide.

Varroa mites

To maintain healthy honey bees, beekeepers need to monitor and control the Varroa mite in their beehives. This includes periodic inspections to determine the infestation level before taking appropriate control measures.



Despite being critically needed by beekeepers, the process of discovering, developing and registering a new varroacide is extraordinarily difficult. Finding the right product not only requires years of research development and a significant financial investment, but also demands a long-term commitment to pollinator health. For 30 years, Bayer has been an industry leader in honey bee research and this effort extends well beyond its own laboratory doors.





Bee health situation in North America
Interview with Dick Rogers, Research Entomologist and Manager at the Bayer North American Bee Care Center

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In this interview, Dick Rogers, Research Entomologist and Manager at the Bayer North American Bee Care Center takes a look at honey bee health and explains why monitoring of beehives is important to check the health of bees throughout the year.



“Only by working together can we make a difference to honey bee health.”

Dick Rogers, Research Entomologist and Manager at the Bayer North American Bee Care Center explains some of the objectives behind the Healthy Hives 2020 initiative, which brings many stakeholders with an interest in honey bee health together to look for solutions to the challenges bees face in our modern world.



As a beekeeper, what are you doing at Bayer to improve bee health?

In this interview, Dick Rogers, Research Entomologist and Manager at the Bayer North American Bee Care Center takes a look, as a beekeeper, at the challenges facing honey bees and how Bayer’s Bee Care Program aims at addressing some of the issues.



Varroa destructor

The Western honey bee’s biggest enemy

The Western honey bee’s biggest enemy is called Varroa destructor. The mite is a huge threat to the health of the bees as it transmits dangerous diseases.




The Varroa mite is regarded as the greatest pest to the western honeybee.
Check our short animation



Additional articles related to the topic

The Varroa Mite

To learn more about the parasitic Varroa mite, one of the biggest threats to honey bee health, check the following publication.

For beekeepers:
Tools for Varroa Management

A guide to effective varroa sampling & control

Protection in the Bee Hive

Learn more from an experienced beekeeper about the practical aspects of Varroa management.

Bayer, Division Animal Health

If you would like to learn more about Bayer’s division Animal health, use the following link

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