Mid-Season Regional Trends in Varroa Mite Populations

As the beekeeping season progresses, the Atlantic Tech Transfer Team for Apiculture has been continuing to survey regional Varroa mite levels. Our team has now completed the second trial of the season which assessed mite levels mid-season. Continue reading this week’s blog to learn more about mid-season trends in Varroa mite populations across the Maritime region, and for insight on a comparison of this year’s mite levels with 2024 and 2025.

Mid-Season Regional Trends in Varroa Mite Populations

The second trial of ATTTA’s Varroa mite survey consisted of 16 beekeepers (7 in Nova Scotia, 6 in New Brunswick and 3 on Prince Edward Island). The second trial took place between July 1 and August 11, 2026 following wild blueberry pollination, and consisted of samples from 57 colonies. These colonies were all from commercial beekeepers who provided pollination services.

Overall, the average mite load for trial one was 0.09%, 84% of colonies had 0% mite load, and 3.5% of colonies had a mite load greater than 1% (Figure 1; Figure 2). The average number of bees per sample for trial two was 316, with a target sample size of 300. In comparison, in 2025, the average mite load for trial two was 0.3% and in 2024 the average mite load was 0.16% (Figure 1)¹. 

Figure 1. Comparison of average Varroa mite loads in the Maritime region between 2024 to 2026 during the middle of the beekeeping season.

Between trial one and trial two Varroa mite levels slightly increased, which demonstrates the usual trend of levels increasing as the season progresses. However, the increase in levels between trial one and two for the 2026 season is less than that of the 2025 or 2024 season. This is an interesting observation that needs to be investigated further as there are multiple reason why a smaller increase in mite levels has been observed. This could be due to random sampling, and there is not a true difference between seasons, or beekeeper management practices are having a positive impact on keeping mite levels low throughout the season (i.e. effective spring treatments, monitoring, and/or providing mid-season treatments). Following the end of the survey, the team will survey all participants on their management practices to better understand these trends. Additionally, following trial three, it will be known what the mite levels were, on average, at the end of the 2026 beekeeping season.

Figure 2. Comparison of Varroa mite loads in the Maritime region between 2024 to 2026 during the middle of the beekeeping season.

After three seasons of data collection, and one more trial to be completed in September, the team has gained a solid understanding of the range of mite levels within the Maritime region at discrete time points in the beekeeping season. Understanding what the range of mite levels are early, mid and late season allows beekeepers and researchers to understand when mite levels deviate from what is typical, which can occur for a variety of reasons such as management practices, efficacy of products and changing climate.

Beekeepers must remain vigilant when monitoring for mites, and practice integrated pest management. A reminder to beekeepers that it is recommended to maintain mite levels below 1% throughout the beekeeping season. For questions regarding mite management and treatment please reach out to the ATTTA team. We would like to thank all beekeepers who participated in trial two of our survey. We will be reporting on trial three of the survey, and the final results of the three-year project, later this fall.

References

1.      Atlantic Tech Transfer Team for Apiculture. 2025. Maritime regional survey on the prevalence of Varroa mites (Varroa destructor) in western honey bee (Apis mellifera) colonies, and the efficacy of amitraz for treatment. https://www.perennia.ca/wp-content/uploads/2018/03/Varroa-mites-REPORT-2025.pdf

Biosecurity is one of the simplest and most effective ways beekeepers can reduce the spread of diseases. Many honey bee diseases persist in wax, comb and hive materials for long periods, making contaminated equipment a major source for reinfection. Keeping up with biosecurity practices in the hive, through regular cleaning, disinfecting tools and sanitizing equipment, helps prevent pathogens from moving between colonies and supports long-term colony health. This includes everything from flaming hive tools to washing bee suits and gloves, because any surface that comes into contact with wax, honey, brood, or debris may carry infectious material.

Biosecurity Practices for Healthier Honey Bee Colonies

Biosecurity begins with understanding how long pathogens can survive in hive materials. Vairimorpha (formerly Nosema) spores, for example, can be killed by heating hive tools to 60°C for 15 minutes or combs to 49°C for 24 hours¹. These spores can survive for a year or more outside of the host, so contaminated equipment can reinfect colonies if equipment is not properly disinfected ¹. Fumigation with 80% acetic acid is recommended to fully eliminate Vairimorpha spores ¹. There will be more information about fumigating hives in a future blog post.

American foulbrood (AFB), caused by Paenibacillus larvae, is even more resilient. AFB spores can survive for decades in hive materials and persist in wax, propolis, and honey for up to 80 years^2,3. AFB spores in wax can be destroyed at 121°C for 30 minutes ².Scorching wooden equipment with a blowtorch is a common practice, but this method does not destroy all spores². While flame sterilization and chemical cleaning remove most microorganisms, AFB spores are extremely resistant, and common disinfectants such as acetic acid and bleach do not reliably eliminate them⁴. In confirmed AFB cases, the only effective solution is to euthanize the colony and dispose of all contaminated equipment. 

Although European foulbrood (EFB) is not spore-forming, it can remain viable in comb for years, and contaminated equipment can contribute to the spread of disease between colonies⁵. Regular cleaning and sanitizing of hive tools, smokers, gloves, and supers can reduce the transmission of EFB⁶.

 Figure 1: Blowtorch and hive tools (ATTTA ©, 2022)

Flaming hive tools is essential to prevent cross-contamination because these tools frequently contact wax, brood frames, and debris. Metal hive tools reach sterilizing temperatures much more rapidly under a propane torch, because propane flames exceed 1000°C, applying heat until wax and propolis residues burn off is sufficient to kill AFB or Vairimorpha spores on metal surfaces^1,2,7.

Protective clothing such as bee suits and gloves can also contribute to disease transmission, as they frequently encounter brood frames, wax, honey and other debris. Equipment and clothing should be cleaned thoroughly after use in an apiary to reduce the risk of spreading pathogens⁴. Washing bee suits regularly and replacing gloves helps prevent spores, bacteria, and parasites from moving between colonies or apiaries. Disposable gloves are a great way to minimize spread of disease between colonies. These simple hygiene practices support stronger colonies.

Figure 2: Beekeeping with disposable gloves (ATTTA ©, 2025)

Biosecurity works best when practiced consistently rather than only in response to disease. Many pathogens persist in wax, comb, and hive debris for long periods, so routine sanitation, cleaning hive tools, washing protective clothing, sterilizing equipment between apiaries, and removing contaminated materials all greatly reduce the risk of transmission. These small, regular steps help maintain healthier colonies and strengthen disease prevention throughout the apiary.

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. Stainton, K., 2018. Recent Research on Nosema. National Bee Unit. Available at: https://www.nationalbeeunit.com/assets/PDFs/3_Resources_for_beekeepers/articles_reports/BBKA_news/BBKA_59_Recent_research_on_Nosema_BBKA_18.pdf (Accessed 26 August 2026).

2. Hansen, H. and Brødsgaard, C.J., 1999. American foulbrood: a review of its biology, diagnosis and control. Bee World, 80(1), pp.5-23. 

3. Sammataro, D. and Avitabile, A. 2021. A Beekeeper’s Handbook: Fifth Edition. Cornell University Press

4. Meredith, B., Parkinson, B. and Walker Bravo, A., 2024. Thriving Hives: Cleaning and Sterilizing Beekeeping Equipment.

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. Government of Alberta, 2021. European Foulbrood. Available at: https://open.alberta.ca/dataset/3df95a52-ed96-4ae7-96d6-f4944ecc63bf/resource/17048d92-ac45-42ce-b74b-9afd6528c5b2/download/af-european-foulbrood-fact-sheet-2021-03.pdf (Accessed: 17 August 2026). 

7. Construction Safety Nova Scotia (n.d.) Propane torch – safe work practices. Available at: https://constructionsafetyns.ca/safe_work_practices/propane-torch/ (Accessed: 13 August 2026).