Wax is one of the most important structural components of a
honey bee colony. It is the footing of what goes on inside the hive,
from storing pollen and nectar to allowing bees to complete their life
cycle. As comb ages through repeated brood cycles, its physical properties
change. Comb darkens due to the accumulation of debris, and older comb
(typically 4-5 years old) can retain substances that affect colony health.
Regular comb replacement is an important management practice for maintaining
healthy colonies.
Wax and Comb
as Reservoirs for Accumulation of Agrichemicals, Pests, and Disease
Beeswax is a lipid-based material composed primarily of
fatty acid esters, hydrocarbons and free fatty acids 1. Wax allows
lipophilic, fat‑soluble compounds, to bind to it 2. Wax also
has a porous structure that allows residues to adsorb and persist within the
comb 1. Contaminants such as spores, debris and agrochemical
residue can become trapped in comb and remain there for long periods 3,4. Once
built, honey bees do not readily remove or metabolize wax, so contaminants
accumulate over time.
Figure 1: Frame being pulled out of a hive (ATTTA ©, 2021)
Several honey bee diseases can persist in wax and brood
comb. European foulbrood (EFB), caused by Melissococcus plutonius,
remains viable in comb for several years 5. The
bacterium has also been shown to be present in symptomless colonies due to its
persistence in wax debris, indicating ongoing contamination within a
colony 6. Experimental work has demonstrated that
adult bees become colonized after ingesting approximately 10,000 bacterial
cells per bee, meaning that even moderate contamination of wax debris can cause infection 10.
American foulbrood (AFB), caused by the spore-forming
bacterium Paenibacillus larvae, is another disease that can
persist in comb. This is because the spore stage of this bacterium is extremely
resilient to the environment, surviving in wax, propolis and honey for up to 80
years 7. Honey bee larvae can become infected after
ingesting as few as ten spores, so even trace contamination of
brood comb can initiate disease 11.
Chalkbrood caused by the fungus Ascosphaera apis also
leaves long-lasting spores. These spores remain in hive material for up to 15
years 7. Spores present in comb can infect developing brood due
to the durability of the spores. Experimental work has shown that
approximately 1000 spores per larva are enough to establish
infection, meaning that contaminated wax can easily maintain the disease
when environmental conditions favour growth of the fungus 12.
Vairimorpha (formerly Nosema) spp.
also interact with hive materials. Vairimorpha spores can remain viable for up
to a year in honey and fecal material, even at freezing temperatures 7,8. A
study has shown that the minimum dose capable of causing a detectable infection
can be as low as 1.28 spores per bee, with a median infective dose of 149
spores per bee 13. Adult bees defecate inside the hive during
cold weather, so Vairimorpha spores can accumulate on comb surfaces and be ingested by
other bees over time.
Figure 2: Dark comb (ATTTA ©, 2021)
Recent research has shown that wax from dead colonies can
contain detectable levels of honey bee viruses, including Deformed Wing Virus
and Black Queen Cell Virus for at least 30 days 9. Freezing
does not reduce viral load, and only high-dose electron beam irradiation
(35-45kGy) has been shown to decrease virus levels 9. This
research is still developing, and it is unknown how significant this is for
transmission inside hives, but important for beekeepers to be aware of.
Wax can also absorb agrochemicals used inside and outside of
the hive. Residues from Varroa mite treatments, as well as other insecticides,
fungicides and herbicides, have all been detected in comb 4.
Some compounds have been found to occur at high
concentrations, including amitraz residue, a product applied by
beekeepers for treating Varroa mites, ranging from 5 to 464 µg/kg, and
insecticides ranging from 1 to 464 µg/kg, brought in by foragers 4.
Even when agrochemicals degrade, their metabolites can remain in wax. Chronic,
low-level exposure may contribute to sublethal effects on honey bee health and
allow pests to develop resistance.
Comb older than 4-5 years can accumulate pathogens, viral
particles and agrochemical residue because honey bees never remove or replace
it themselves. Regular comb replacement is one of the most effective ways
beekeepers can reduce buildup and support healthier colonies. A future blog
will explore comb rotation in more detail and how beekeepers can use it to
maintain cleaner, safer hives for honey bees.
Written by Kaitlyn Newton, ATTTA Seasonal Apiculturist
Connecting with ATTTA Specialists
If you’d like to connect with ATTTA specialists or learn more about our program, you can:
visit our website at https://www.perennia.ca/portfolio-items/honey-bees/
Email attta@perennia.ca
References:
1. Meng, Q.,
Huang, R., Yang, S., Jiang, W., Tian, Y. and Dong, K., 2025. An Overview of the
Adverse Impacts of Old Combs on Honeybee Colonies and Recommended Beekeeping
Management Strategies. Insects, 16(4), p.351.
2. Atlantic
Tech Transfer Team for Apiculture, 2017. Comb Rotation. https://www.perennia.ca/wp-content/uploads/2018/04/11-comb-rotation-eng.pdf
3. Wu,
J.Y., Anelli, C.M. and Sheppard, W.S., 2011. Sub-lethal effects of pesticide
residues in brood comb on worker honey bee (Apis mellifera) development and
longevity. PloS one, 6(2), p.e14720.
4. López,
S.H., Lozano, A., Sosa, A., Hernando, M.D. and Fernández-Alba, A.R., 2016.
Screening of pesticide residues in honeybee wax comb by LC-ESI-MS/MS. A pilot
study. Chemosphere, 163, pp.44-53.
5. León-Door,
A.P., Pérez-Ordóñez, G., Romo-Chacón, A., Rios-Velasco, C., Órnelas-Paz, J.D.,
Zamudio-Flores, P.B. and Acosta-Muñiz, C.H., 2020. Pathogenesis, epidemiology
and variants of Melissococcus plutonius (Ex White), the causal agent of
European foulbrood. Journal of Apicultural Science, 64(2), pp.173-188.
6. Budge,
G.E., Barrett, B., Jones, B., Pietravalle, S., Marris, G., Chantawannakul, P.,
Thwaites, R., Hall, J., Cuthbertson, A.G. and Brown, M.A., 2010. The occurrence
of Melissococcus plutonius in healthy colonies of Apis mellifera and the
efficacy of European foulbrood control measures. Journal of
invertebrate pathology, 105 (2), pp.164-170.
7. Sammataro,
D. and Avitabile, A. 2021. A Beekeeper’s Handbook: Fifth Edition. Cornell
University Press
8. MacInnis,
C.I., Keddie, B.A. and Pernal, S.F., 2020. Nosema ceranae (Microspora: Nosematidae): a
sweet surprise? Investigating the viability and infectivity of N.
ceranae spores maintained in honey and on beeswax. Journal of Economic
Entomology, 113(5), pp.2069-2078.
9. Colwell,
M.J., Pernal, S.F. and Currie, R.W., 2024. Treatment of waxborne honey bee
(Hymenoptera: Apidae) viruses using time, temperature, and electron-beam
irradiation. Journal of Economic Entomology, 117(1), pp.34-42.
10. Sebastian Jose, M., Bezerra da Silva, M.C., Obshta, O.,
Masood, F., Thebeau, J.M., Biganski, S., Raza, M.F., Camill, M.P., Prieto,
E.T., Edirithilake, T. and Kozii, I., 2025. Antimicrobial control and temporal
dynamics of M. plutonius colonization in adult worker honey bees (Apis
mellifera). PLoS One, 20(5), p.e0322770.
11. Locke, B., Low, M. and Forsgren, E., 2019. An integrated
management strategy to prevent outbreaks and eliminate infection pressure of
American foulbrood disease in a commercial beekeeping operation. Preventive
Veterinary Medicine, 167, pp.48-52.
12. Knoblauch, T., Jensen, A.B., Mülling, C.K.,
Aupperle-Lellbach, H. and Genersch, E., 2024. Chalkbrood Disease Caused by
Ascosphaera apis in Honey Bees (Apis mellifera)—Morphological and Histological
Changes in Infected Larvae. Veterinary Sciences, 11(9), p.415.
13. McGowan, J., De la Mora, A., Goodwin, P.H., Habash, M.,
Hamiduzzaman, M.M., Kelly, P.G. and Guzman-Novoa, E., 2016. Viability and
infectivity of fresh and cryopreserved Nosema ceranae spores. Journal of
microbiological methods, 131, pp.16-22.
