Fumigating Hives with Acetic Acid

Maintaining sanitary hive equipment is important for disease management in beekeeping. Routine cleaning and replacement removes old wax, propolis, and debris, but certain pathogens can persist on hive surfaces and weaken colony health. Acetic acid fumigation is an effective way to chemically sterilize used equipment, particularly when colonies show signs of chronic infection or poor health. 

Fumigating Hives with Acetic Acid

Acetic acid (CH₃COOH) is commonly found in vinegar, but the concentration used for hive fumigation is significantly stronger. When fumigating equipment, an 80% acetic acid solution is recommended ^1,2. This strength of acetic acid is classified under Canadian WHMIS as a Flammable Liquid (Category 3), Skin Corrosion (Category 1), Serious Eye Damage (Category 1), and Acute Toxicity (Inhalation, Category 3) ³. These classifications reflect the hazards associated with this chemical and highlight the need for careful handling during fumigation. 

Vairimorpha (formerly Nosema) is a microsporidian disease that infects the midgut of honey bees. Spores are shed in fecal material and accumulate on hive surfaces, including comb, frames and hive walls. Vairimorpha spores can remain viable for up to a year in honey and fecal material and can cause a detectable infection at a low number of spores ^4,5,6. Since spores persist in the environment, they can cause reinfection of the disease in an apiary for extended periods. Periodically fumigating all equipment destroys the spores living in the environment, and supports healthier colonies when equipment is reused. Acetic acid fumigation is also effective against wax moth of all life stages when equipment is being stored⁷.

Acetic acid fumigation, however, does not kill Paenibacillus larvae, the causative agent of American foulbrood (AFB) ^1,2. AFB spores are exceptionally resilient and can survive in hive materials for decades. Equipment contaminated with AFB cannot be disinfected using acetic acid and must be destroyed according to regulatory guidelines. 

Because 80% acetic acid is corrosive, flammable, and hazardous to inhale, appropriate personal protective equipment is required. Recommended protective equipment includes chemical-resistant gloves, goggles/face shield, a respirator suitable for acid vapors, and protective clothing. 

There are two methods commonly used in beekeeping to fumigate equipment. The indoor method requires an isolated room heated to 25-30 °C ¹. Four boxes with frames should be stacked tightly on a closed pallet with no bottom boards, sealed with tape to ensure close contact between boxes, and covered with an inner cover ¹. A tin container containing 500 mL of 80% acetic acid should then be placed on the top of frames, with an empty super on the very top ¹. The acid will take approximately a week to evaporate ¹. The room should remain closed, with warning signs placed to prevent exposure to the fumes ¹. After fumigation, let the equipment air out for several days before using ¹.

The outdoor method is similar to the indoor method previously described. Ensure the stack of boxes is sealed as tightly as possible with vapor barrier plastic, stretch wrap, or tape ¹. Place the stack in an area with no wind and full exposure to the sun and only fumigate outside when temperatures are between 20-30 °C ¹. 

Fumigation with acetic acid is an effective sanitation tool for beekeepers managing hives with chronic exposure to Vairimorpha spp. When paired with other biosecurity measures and proper hygiene, fumigation can reduce environmental spore load and support healthier colonies. Caring for honey bees includes caring for the equipment they depend on!

 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. Kelly, P., n. d. Fumigating with Acetic Acid to Decontaminate Brood Chambers. Honey Bee Research Centre, University of Guelph. Available at https://hbrc.ca/acetic-acid-fumigation-2/ (Accessed August 21 2026)

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

3. Workplace Hazardous Materials Bureau, Health Canada, 2025. Hazardous substance assessment - Acetic acid. Government of Canada. Available at https://www.canada.ca/en/health-canada/services/environmental-workplace-health/occupational-health-safety/workplace-hazardous-materials-information-system/hazardous-substance-assessments/acetic-acid.html (Accessed August 21 2026)

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

5. 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.

6. 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.

7. National Bee Unit, 2025. Fumigating Comb. Available at https://www.nationalbeeunit.com/assets/PDFs/3_Resources_for_beekeepers/Fact_Sheets/Fact_14_Fumigating_Comb.pdf(Accessed August 21 2026).

 

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