Mite monitoringVarroa

Why monitor for Varroa?

In addition to serving as Veto-pharma’s United States technical adviser, Phil Craft also writes a Question/Answer column – “Ask Phil” – in Bee Culture magazine. An upcoming column will feature the following response to one of the magazine’s readers. We think it might be of interest to our readers as well. This will be the first of a regular series of contributions by Phil, many drawn from his columns in the magazine. Phil’s Bee Culture columns can be found at He encourages beekeeper’s questions, some of which will be selected for publication, and all of which will receive personal replies. You may email him at: or

A beekeeper in Indiana writes:

All of you experts tell us to treat for varroa mites, but they also say to monitor for mites. Though all the beekeepers that I know who don’t lose most of their bees every year, treat EVERY year. So if we are going to treat anyway, why monitor?

Phil Replies:

Monitoring alerts beekeepers to high varroa levels, but it accomplishes much more than that when done correctly. Let’s go back in time, to when varroa mites first swept the U.S. with devastating results, to understand how monitoring practices developed and how they have changed. When the first treatment was approved in the early 1990’s beekeepers seized upon it eagerly. Monitoring was not common practice because there were really no decisions to be made. Mites were pervasive and there was only one registered product to control them: Apistan, containing the active ingredient fluvalinate. Not treating meant total colony loss. Varroa treatments were typically “by the calendar”, meaning an application in early spring and another in late summer, without prior monitoring. This method was successful with the majority of mites – those susceptible to fluvalinate – but a few possessed a degree of natural resistance. They reproduced and passed on enhanced resistance to their numerous offspring in a process similar to that in which over-use of antibiotics in humans has created MERSA and various other drug resistant strains of bacteria.

Researchers feared that years of regular exposure to a single chemical agent would create a super strain of varroa impervious to our only available weapon against them. They started urging beekeepers to monitor in order to assess the level of infestation in their hives and to treat only when necessary. […]

Thanks to the diligence of researchers and the commercial importance of honey bees, we now have a variety of tools to use against Varroa: some synthetic and some organic, some having an immediate effect and some which act over time to kill emerging as well as adult mites (and also a few which are popular but ineffective). With all these options comes the need for solid data to enable individual beekeepers to make the best choices for their situations. Resistance is still a concern and reason enough to monitor, though alternating different types of treatments can mitigate the problem. But monitoring can also ensure timely treatment. Knowing the mite count in early spring gives a beekeeper information to direct a strategy. A moderate to high number would indicate immediate treatment to save the colony, even if that meant missing part or all of the honey flow, because most miticides cannot be used with supers in place. A beekeeper with a low or moderate count has more options. Depending on the number, he or she might decide to act at once, or to postpone treatment until supers are removed.

Having clear data about the mite load can also help guide a beekeeper through the maze of available treatment options. In the United States there are currently eight miticides registered for the control of varroa mites, including Apivar and ApiLifeVar which are distributed by Véto-pharma. The various products involve different methods of application, modes of action, effectiveness, concerns about residues, and likelihood of varroa resistance. Local bee inspectors and/or extension specialists may have opinions and recommendations about which treatment is most appropriate for your situation. Other beekeepers are sure to, but it’s said that if you ask ten beekeepers a question, you’ll get eleven different answers. Listen to the ones who have the lowest losses among their own colonies.

The fact that so many confusing choices exist highlights another reason for monitoring varroa mites: to gauge the effectiveness of mite management strategies. Could varroa be developing resistance to the chemical you’ve been using for years? Is the organic treatment you read about online really working? Many beekeepers feel safe because they conscientiously use some form of mite control. When their colonies die, they ascribe the losses to CCD, pesticides, or some other cause, and that may be the case. But. There is no way to know if a treatment is effective, or if it was employed in time, without monitoring both before and after.

Regular monitoring can also reveal sudden increases in varroa loads, which may occur if your hives are located near those of other beekeepers. One small commercial beekeeper I know tells me that a hobby beekeeper placed some hives near one of his apiaries. The hobbyist doesn’t treat for Varroa. My friend can tell just by looking at mite counts which samples come from that apiary. His treated colonies, which rob his neighbor’s Varroa weakened ones, carry mites back with them and always show a higher mite count than those in his other, more isolated hives. He has to keep a closer watch on those. There’s no one-size-fits-all answer for how often you should monitor any more than there is for how often to treat. It’s typical for commercial beekeepers to monitor once a month. For small beekeepers and hobbyists, I would suggest as a minimum checking in the early spring, then after honey supers are pulled, after the completion of each treatment for Varroa, and again in the fall. That sounds like a lot, but it isn’t always necessary to monitor each hive every time. If you have fewer than ten, I recommend checking them all, but in an apiary with more than that I suggest randomly sampling eight or so, including any which seem to be building up slowly or which give you other reasons for concern.

How high is too high? Interpreting the results of monitoring could be the subject of another column – or a short book. It depends on the monitoring method, the time of year at which samples are taken, and the region of the country in which the hives are located. The best guidance might come from your state apiarist or local association.

Good information is also available at the websites of the Honey Bee Health Coalition: and the Bee Informed Partnership:

Controlling Varroa is no longer as simple as treating by the calendar. It’s about knowing whether to treat, when to treat, and whether your treatment was effective. Monitoring is a tool you need to be successful.

Monitoring at the apiary