In the light of recent research findings we should be asking ourselves whether varroa really is the cause of the problems occurring with honeybees worldwide. Download this document here.

At the beginning of 2014 the global scientific community researching bees reached the consensus that varroa is the cause of the problems in the apiary industry. In the words of Peter Neumann, head of COLOSS, the honeybee research association in Europe, in his e-mail dated 26 September 2014: “Varroa destructor is the major threat to apiculture with honeybees of European stock.”

This narrowing towards a single cause comes as a surprise. After all, many organizations in the sector had made it clear in many ways that “multiple factors are causing the problems with honeybees”. The scientific basis for this shift in vision is unclear, at least, it does not seem to be backed up by new facts. To our knowledge, no well-founded estimates have been made of the threats posed by the individual factors, which are still mentioned as causes of bee mortality.

Surprisingly, Neumann only mentions the European honeybee Apis mellifera. Apparently he is unaware of the fact that Apis scutellata is also suffering decline, in East Africa for example (varroa occurs there too).

Consensus in the scientific world

It is understandable that COLOSS wants to send a clear message to beekeepers, bureaucrats and politicians in the various different countries and as well as to the international bodies. It is also understandable that COLOSS wants to draw attention to a ‘pathogen’, because such a pathogen can be easily understood by everyone. And it might also be a strategy to rank pathogens above other causes mentioned frequently. All this has little to do with science, knowledge or insight. COLOSS is a data generator, and due to a coding error, the production process has ground to a halt.


Varroa falls under our disease model. The main objection to this shift in opinion is purely technical. A problem or disease is seldom monofactorial. However, people do consider the role of varroa as transmitter of viruses to be part of the varroa problem, but this is mainly convenient so they can hold onto their previously adopted points of view. Similar phenomena occur in nature with other pollinators and with higher organisms. The most important factor in the phenomena of reduced biodiversity occurring worldwide, that species are disappearing as well as bee mortality, is being overlooked. Some see bees as the ‘canary in the coal mine’, as a warning for something happening in the environment.

The statement of consensus on varroa is above all evidence of an incorrect, superficial diagnosis. It almost automatically implies that the organizations affiliated to COLOSS will not be able to come up with effective solutions, or to make recommendations about such. As long as one considers ‘varroa in itself’ as the main problem for beekeepers, there will be no progress towards finding better management tools for beekeepers for the future. Again, the motto: “Past performance does not offer any guarantee for the future” applies.

Varroa control

It is clear that over the past 30 years, all the resources dedicated to combatting varroa have not actually contributed to preventing bee decline or colony losses. According to Peter Neumann, “well-established and proven” varroa treatments (formic acid, oxalic acid, thymol) should be used.

These compounds promote mite fall and thus reduce the numbers of varroa mites in a colony. However, the effect on mortality levels and the numbers of colonies lost is generally negligible or absent. The reason for this is because current treatments and methods do not interfere with the processes that lead to virulence of the mites, nor do they act on the processes which are responsible for colony losses, these are universal bacterial processes, including viruses. In bee science, these are not being addressed collectively. There is nothing to be found in scientific publications about bees or people have indicated they are not knowledgeable about the determining factors.

The positive effects of ‘varroa treatments’ are significantly less than the adverse effects due to other factors, such as the local conditions, the weather and the occasional lack of suitable food for the bees.

Adverse effects of treatments

All varroa treatments have adverse effects on the bees, on their reproduction and on colony behavior. Some of these products often result in bees leaving the hives. It has also been demonstrated that continuous treatment with chemicals has led to varroa adapting itself, possibly through the bacterium-virus complex. This is true for any treatment which is intended to combat varroa. Often ‘varroa control’ has more adverse effects than the varroa problem itself. The recommendation to treat bee colonies for varroa has led to a situation in which the blame for ‘winter mortality’ has been placed by beekeeper because he may not have administered the treatment properly (‘beekeeper incompetence’). This masks the true cause of bee mortality.

Incorrect statements

By now, experienced beekeepers have heard the varroa message hundreds of times, thanks to the marketing efforts of research institutions, communicated via beekeeper associations.

However, every beekeeper should be aware that many of the statements made about varroa are simply incorrect, or are only correct within a limited scientific scope, the so-called ‘half-truths’. An example of a pertinent inaccuracy is that various treatments help because the numbers of varroa mites are reduced. Bee colonies still struggle even if varroa is present in small quantities and is not treated, or even if no varroa is present in the colony. Bee colonies can thrive even in the presence of many varroa, the bees do not die from varroa.

A striking example of a half-truth is the assumption that the “Varroa mite comes from Asia and had spread from there across the whole world”. It would be better to answer the question: “How was the varroa mite able to spread to other environments and successfully establish itself?” Here too, it is clear that varroa has different mechanisms at its disposal in order to establish itself, so not only via hygienic behavior. The half-truth must therefore be supplemented with yet another half-truth.

Living with varroa

John Miller, former president of the California State Beekeepers Association, said: “You can imagine how difficult it is to kill an assailant that resides in an organism to which it is very similar”. Watch his presentation here.

Beekeepers cannot eradicate varroa, having varroa-resistant bees is just a promise, at the most. They have a need and the bee system enables this to function better. So perhaps it would be fairer to say “Apparently varroa is a part of the bee system nowadays, there might be even useful functions of varroa”.

Scientific publications about bee viruses do not go beyond describing these viruses (albeit with extensive genome analyzes), where and when these viruses occur and which symptoms they cause in bees. They do not describe the functions that these viruses have and what their presence means for the bee colonies. And therefore, the viruses are usually also designated as ‘cause’.

It has definitely never been proven that viruses (DWV for example) are transmitted by varroa. At most, it may have been demonstrated that some viruses occur in both mites as well as in bees. The idea that viruses are the cause of the problems with the bees is primarily a result of improved detection techniques, the fact that virologists have started to take an interest and the assumption that viruses cause ‘diseases’. A virus is essentially a piece of genetic material that primarily produces proteases (enzymes that decompose proteins).

Varroa is a result, not a cause – underlying process

We have discovered what the fundamental process is; this leads to the dominant presence of varroa, as well as some other factors, which contribute to varroa being able to thrive under circumstances which are less favorable for the bees. There is also a clear and unambiguous explanation for the explosion in the number of mites, such as occurred in 2014.

This involved the recurring underlying bacterial process. This process can be easily influenced by introducing certain changes in the food. For the time being, only ensuring adequate foraging grounds does not offer sufficient prospects. High bee decline even occurs in areas rich in flowering plants. However, what we can do is to give the bees supplements to improve colony condition, just like you’d take extra vitamins and minerals yourself in the winter to stave off a cold or the flu.

See here for additional information about varroa, browse our website for further information or read our proposal for the bee health program (in dutch only).

References are available on request; there is a charge for this service.