Bee Health Assurance Team Update

By Samantha Muirhead, Alberta Provincial Apiculturist

Every spring Provincial Apiculturists across Canada send out an Annual Honey Bee Winterkill and Pest Management Survey to their provincial beekeepers. With the compiled information, the Canadian Association of Professional Apiculturists (CAPA) prepares a report on the status of honey bee health across the country. For more information on national results from 2020 to 2021, as well as previous years’ findings, you can go to https://capabees. com/category/extension/overwintering-losses/. The survey asks commercial beekeepers a series of questions regarding their winter losses, management practices, queen sources, and potential causes of colony loss. The survey results are important and help with forecasting emerging pest and pathogen issues, developing best management practices, and justifying the emergency registration of new miticides and medications when required, to name a few.

In Alberta, beekeepers on average lost an unusually high number of colonies over the 2021/2022 winter, 37%, 50.5% if you include colonies that came out of winter with less than three frames of bees. the top three causes of winter losses reported by beekeepers in the survey in order of importance were Varroa mites, weather, and poor queens. This article will focus on the number one ranking issue: Varroa mites. We will look at how Varroa may have increased winter losses, as well as a few tips on how to manage Varroa mite populations in the future. Stay tuned for a more detailed report early next year that will inform beekeepers of trends, overwintering practices, and management practices utilized by Alberta’s commercial beekeepers.

In 2021, the Bee Health Assurance Team (BHAT) reported Varroa mite infestation levels above the economic threshold (the point at which you should apply a treatment to avoid losing income from lost colonies/honey production) in both the spring (greater than or equal to 1% mite infestation) and the fall (greater than or equal to 3% mite infestation). This was not due to beekeepers deferring treatment (100% of survey respondents treated their colonies in either the spring, fall, or both); it was because applied treatments were unable to reduce Varroa mite populations below the economic threshold before mites had done irreversible damage to colonies.

One of the most important things a beekeeper can do to prevent Varroa mite levels from getting above the threshold is monitor. Monitoring should take place throughout the beekeeping season but most importantly before and after treatments are applied. This will allow a beekeeper to make informed decisions on when or if to apply a treatment, if the treatment has worked effectively, and if another application is required. Unfortunately, according to the survey results, only 60% of beekeepers in the spring and 76% in the fall monitored their colonies for Varroa mites. Of those beekeepers who monitored their colonies, only 39% of beekeepers in the spring and 48% in the fall monitored before and after treatment. This means that less than 50% of beekeepers are actually making well-informed decisions regarding Varroa management in Alberta.

Monitoring is only one aspect of Varroa mite management. Other factors could be contributing to high Varroa levels in your colonies and should be considered. 1. Timing and type of treatment: • Treatments may be dependent on ambient temperature, colony strength, presence or absence of brood, number of brood chambers, and humidity. Make sure to follow the label on all treatments. • According to the survey results for fall 2021, oxalic acid sublimation was the preferred miticide (52%). In order for oxalic acid to be effective, it requires that your colonies are broodless. In 2021, because of the warm fall, most beekeepers were applying oxalic acid when the colony was still full of brood. The result was little to no drop in mite population.

2. Varroa mite populations above threshold after treatment is applied: • Chemical treatments that eliminate 100% of a pest population do not exist in any industry. • If your mite population is high and the product is 90% effective, your infestation may still be above the economic threshold after treatments are applied. For example, if you have 1000 bees and 300 mites in your colony with a treatment that is 90% effective, you will still have 30 mites, after the treatment, which is over the economic threshold for both spring and fall. This may only happen in one or two colonies in an apiary with abnormally hive varroa populations but these colonies will act as a source of reinfection.

3. Miticide is no longer effective: • Beekeepers have experienced this in the past with Apistan and Checkmite, and currently there are concerns that Apivar is less effective than when it first came on the market in Canada. In 2021, the BHAT received reports about the efficacy of Apivar. Surveyed respondents reported that in the spring and fall, approximately 40% and 24% of beekeepers who used Apivar reported that that it was not effective at controlling their mite population. However, of those beekeepers, only 40% in the spring and 20% in the fall monitored before and after treatment. The Alberta Tech Transfer Team (TTT) and BHAT will be collaborating this year to determine how effective Apivar is at reducing varroa mite populations. If you are interested in participating, please reach out to the TTT. • Under/over dosing, leaving strips in the colony for longer than recommended, reusing strips, using the same miticide consecutively are all practices that decrease the efficacy of a treatment and promote the development of resistant mites.

Misapplication or handling of treatment. • Placing treatment in wrong location in the colony. • Leaving the strips exposed to sunlight before application.

To avoid misuse of a pesticide always follow the label, familiarize yourself with the treatment application conditions, and rotate treatments. Remember monitoring is an imperative tool in an effective Varroa management program and if ignored can leave you in a situation where irreversible damage has been done to your colonies.

CORRECTION

In the June 2022 edition of Alberta Bee News magazine, details were provided of locations to buy sponges/pads in Alberta. Currently the use of Oxalic+glycerine together as a treatment for use on honey bees is not approved by the Pest Management Regulatory Agency (PRMA).

Risks of using a treatment not approved by the Pest Management Regulatory Agency

The PMRA only allows pesticides to be registered after there is a science-based evaluation that ensures the risks of applying the pesticide are acceptable. It is illegal to apply a treatment that is no approved by the PMRA. By applying, a treatment that has yet to be approved a beekeeper is putting the health and safety of themselves and their bees at risk and potentially contaminating their honey. Although studies have been done in Canada the data has yet to be published. Currently, we only have information on its efficacy in California and Argentina, where the climatic conditions are much different from those in Canada. Until PMRA approved this method we do not know the impact that it has on colony health, how many applications are ideal, if it will contaminate the honey, what medium is most effective at disseminating the compound, when to apply the treatment, or how effective it is at lowering mite populations.