As we head into the end of the beekeeping season it is important to remember that colony health and winter survival depend on proper colony management. In particular, Varroa mites are the primary cause of colony mortality in Ontario. While beekeepers are treating for Varroa mites they must recognize that all treatments have limitations. These limitations may include such factors as temperature thresholds, timing, incorrect use, and less efficacy than advertised or intended.
This season, there has been confirmation of amitraz (the active ingredient in the product Apivar®) resistance in North America and there is some concern that it is present in Ontario. We are aware of beekeepers with very high levels of Varroa mites this fall. These levels may be due to inherent limitations of treatments, the timing of earlier colony development this season or the success, or lack thereof, of Varroa management throughout the beekeeping season.
While it is now late in the season, and beekeepers should be treating for Varroa, it is crucial that beekeepers:
Continue to sample for Varroa levels in colonies to see if the Varroa levels are under control and treatments are working
Consider further treatments (rotating with a different active ingredient) if the Varroa levels are still too high
Beekeepers should not assume their Varroa levels are under control simply because a treatment has been applied. Beekeepers are strongly encouraged to take the extra steps to check their Varroa levels, the efficacy of treatments and take further action if needed.
We are also reminding beekeepers to use the 2023 Ontario Varroa Monitoring Campaign questionnaire to share their data. This data is important to capture the reality of what is occurring with Varroa and supports future projects addressing this very serious pest.