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February 2022 213
According to official reports, there are almost 16 mil-
lion honey bee colonies in the European Union,
managed by about 600 thousand beekeepers, with
an annual honey production worth almost 2 billion euros.
On top of the value of the direct production of beehive
products, honey bees contribute to pollination services of
agricultural crops and of wild flora, ensuring maintenance
of biodiversity and of healthy agroecosystems. Honey bees
are, however, under huge stress due to intensification of
agricultural practices as well as climatic changes and glo-
balisation, which bring new diseases to bees. Amongst
them is the parasitic mite Varroa destructor, which can lead
to the death of most infested colonies within one year, if no
treatment is applied by beekeepers.
Varroa mites feed on the adult bees and bee pupae and,
during this process, can transmit deadly viruses. Since its
arrival in Europe in the late 70s, varroa now infests most
colonies, and represents the most impactful pathogen
threat for honey bees and the beekeeping industry world-
wide. Beekeepers only have limited solutions to control the
mite without incurring risk of residues in hive products,
secondary effects on honey bees and inducement of treat-
ment-resistant mites. A promising and sustainable solution
emerges from numerous reports worldwide that some hon-
ey bee populations are able to survive mite infestation in
the absence of treatments. These survivor bees develop de-
fences to maintain the parasite population under control.
As this ability can be transmitted to the next generation, it
opens up the possibility for beekeepers to specifically select
and breed for varroa-resistant bees.
Goals and methodoloGy of the eurbest study
In 2017, the European Commission contracted an inter-
national bee research consortium (European Bee Selection
Team = EurBeST) under the lead of the Bee Institute in
Kirchhain, Germany, to answer the following questions1:
What is the status and extent of the honey bee breed-
ing and reproduction market in the EU?
What is known about varroa resistance? Do varroa-
resistant bees exist in the EU? Are they available for
beekeepers to use?
Are beekeepers interested in using varroa-resistant
honey bees? What do they expect when they buy
honey bee queens?
What methods are available for selecting varroa-re-
sistant bees? Do they work?
What are the efforts and costs to obtain varroa-resis-
tant honey bee stock?
The EurBeST consortium involved experts in beekeep-
ing, bee biology, breeding, economics and statistics. They
analysed the EU market for honey bee reproductive mate-
rial (Figure 1) and ran a literature review and expert in-
terviews on the state of play in varroa resistance. Selec-
tion programs on varroa resistance were reported in 20 EU
countries and naturally resistant populations in six. How-
ever, commercially available resistant stock was found to
be present in only four countries.
Customer survey on breedinG stoCk
A customer survey on the current queen market revealed
high expectations, but moderate satisfaction. European
beekeepers want to buy high-quality queens which, most
importantly, express disease resistance and good produc-
tivity. However, they are least satisfied with the disease
resistance compared to the other traits (Figure 2). Almost
50% of the customers trust in selection as an important, or
the only, tool to achieve treatment-free beekeeping. Inter-
estingly, the approval rate was higher in countries with a
long tradition of selective breeding.
the larGest ever study on honey bee seleCtion
As the core part of the EurBeST project, five large-scale
case studies, including seven EU countries and 130 par-
Fig. 1 EU market for honey bee reproductive material
Buechler, R.*, Uzunov, A., Costa, C., Meixner, M., Le Conte, Y.,
Mondet, F., Kovacic, M., Andonov, S., Carreck, N.L., Dimitrov, L.,
Basso, B., Bienkowska, M., Dall’Olio, R., Hatjina, F., Wirtz, U.
EurBeST — A Pilot Study Testing
Varroa-resistant Bees Under
Commercial Beekeeping Conditions
*= corresponding author – Landesbetrieb Landwirtschaft Hessen,
Bieneninstitut, Erlenstrasse 9, 35274 Kirchhain, Germany,
Email: ralph.buechler@llh.hessen.de
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American Bee Journal214
ticipating beekeepers, were carried out (Figure 3). The
EurBeST team identified and selected 23 lines, belonging
to six subspecies and also of mixed origin, from surviving
populations or from varroa-resistance selection programs.
They were tested for their general beekeeping and resis-
tance traits on two different levels: on the one hand by per-
formance testers who extensively compared several lines
within the same apiary, and on the other hand by com-
mercial beekeepers who compared one or several test lines
with their own stock under normal field conditions. With
more than 3,500 colonies tested for one whole season, this
constitutes the largest investigation on honey bee selection
ever conducted in Europe.
hiGher resistanCe of seleCted stoCk
The EurBeST selected lines showed similar survival rates
to the beekeepers’ own stock. While there was on average
not much difference for the general traits (honey production,
defensive behaviour and swarming tendency), the EurBeST
lines clearly outperformed the commercial beekeepers’ own
stock with regard to mite infestation (Figure 4).
In the performance test apiaries, which refrained from
any mite treatment during the one-year duration of the in-
vestigation, some EurBeST lines kept infestation with var-
roa below the 3% infestation threshold for required mite
treatment until the end of the season (Figure 5). Some of the
selected lines demonstrated high productivity, combined
with low varroa infestation.
varroa resistanCe traits
When measuring specific varroa resistance traits, we
observed that infestation levels closely correlate with the
colonies’ hygienic behaviour: On average, higher remov-
al of damaged brood (measured by pin-test) correspond-
ed to lower colony infestation by varroa. Lines with a
selection history for this trait displayed higher levels of
hygienic behaviour (Figure 6). Varroa Sensitive Hygiene
(VSH) also seemed to affect varroa infestation, which
was lower in colonies with a higher VSH. The Recapping
(REC) trait (that indicates inspection of brood cells on
behalf of worker bees) was found to be correlated with
VSH, meaning that it was higher in colonies displaying
a high VSH. However, the connection of this trait with
varroa infestation was not clear, and a similar situation
was also found for the Suppression of Mite Reproduction
(SMR) trait.2
loCal adaptation is important
The case study results also showed strong interactions
between genetic and environmental factors in regulating
honey bee colony general performance as well as varroa-re-
sistance potential. Practically, the same line of bees used in
two different locations may perform very differently, high-
lighting the need for local selection strategies (Figure 7).
Fig. 2 Results of an online survey on expectations and satisfac-
tion about marketed queens by 396 beekeepers from dierent
European countries
Fig. 3 EurBeST case study countries (in yellow) with dots mark-
ing the position of the 130 test apiaries involved. The German
case study included testing sites in Austria and Croatia, and the
Italian one included a smaller, separate case study in Sicily.
Fig. 4 While starting with higher mite infestation levels in
autumn 2019, the EurBeST lines were on average less in-
fested compared to the commercial beekeepers’ own stock
by the end of the test season in summer 2020.
Fig. 5 After a full season without any treatment against varroa,
the infestation of several lines clearly remained below the 3%
infestation threshold for required mite treatment, showing prom-
ising avenues for treatment-free beekeeping (letter codes pres-
ent dierent EurBeST lines, two-letter codes present case study
countries, columns show mean values with standard errors).
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February 2022 215
Commercial beekeepers depend on well-adapted stock to
reduce disease burdens and to achieve sustainable eco-
nomic success.
seleCtion is expensive
As a part of the study, participating queen producers,
performance testers and commercial beekeepers were
interviewed on their production costs and selling prices.
Testing a colony costs 193 € on average, ranging from 273
€ in Germany to 85 € in Greece. The main costs of colony
evaluation derive from testing for varroa resistance. Moni-
toring varroa infestation and testing for hygienic behav-
iour together reach almost 20% of the total costs, while the
highest share of the colony evaluation costs, with more
than 60% of the total, results from assessing specific varroa
resistance traits (SMR, REC and VSH) (Figure 8).
Queen priCe does not Cover the Costs of seleCtion
The average cost for queen production across the study
amounted to 22.58 € per queen, but with huge variation
(from 8.22 € in Poland to 37.30 € in France). The main share
originates from labour costs, which significantly vary be-
tween countries. The average selling price per queen of
23.32 € sometimes does not cover even the pure produc-
tion costs. More significantly, it does not in any way com-
pensate the efforts of a serious and continuous selection
program, including testing, breeding value estimation and
maintenance of the mating stations.
ConClusions and reCommendations from the study
Selective breeding of honey bees is an eicient way to in-
crease productivity, to reduce colony losses, and to improve
bee health. The use of well-selected stock is a major factor of
economic success in commercial beekeeping.
Regional breeding structures are needed to select locally
adapted bees. These include cooperation among breeders,
queen producers and commercial beekeepers, with scientific
support.
Selection for resistance works, but it is costly. Mite infesta-
tion development and hygiene behaviour are useful criteria to
select varroa-resistant stock. However, the costs of testing for
the breeders are high and need to be compensated.
The market for queens must be improved. There is a high
demand from commercial beekeepers for queens selected for
varroa resistance. However, the usual market prices for queens
do not cover extra costs for selection. Subsidising the produc-
tion of high-quality queens could help.
Honey bee breeding needs support. The success of breed-
ing programs depends on their scale and consistent develop-
ment over several years. Considering the high costs for specific
selection methods toward improved varroa resistance, public
funding of the beekeeping breeding sector is recommended
and beekeeper associations should lobby for this.
footnote
1 European Commission, Directorate-General for Agriculture and
Rural Development: EurBeST Pilot Project: Restructuring of the
Honey Bee Chain and Varroa Resistance Breeding & Selection Pro-
gramme, Final Study Report AGRI-2017-0346. Brussels, 2021, DOI:
10.2762/470707
2 Although often used interchangeably, VSH and SMR are different
characters! VSH is defined as the proportion of varroa-infested cells
removed by the bees during pupal development, while SMR de-
scribes the proportion of mites which remain without successful
reproduction during their brood passage.
There is still some misunderstanding, as researchers at one time
assumed VSH as the main responsible cause of SMR. However, we
know by now that some other causes like uncapping/recapping or
the individual course of brood dynamic also contribute to the SMR
expression.
Fig. 6 Dierent expression of hygienic behaviour (measured by
pin-test) among the EurBeST lines. (For colour and letter cod-
ing see Fig. 5.)
Fig. 7 The selected lines outranged beekeepers’ usual stock in
varroa resistance, depending on their adaptation to local envi-
ronmental conditions.
Fig. 8 Contribution of the dierent testing activities to the
overall costs of selection
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