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.