Varroa mite infestation is nearly universal in honey bee colonies and represents one of the biggest threats to any colony’s survival. Beekeepers can choose from a variety of miticides (synthetic or organic chemicals) designed to mitigate the impact of varroa.
Comparing varroa mite treatments among beekeepers we polled, the most popular and effective treatment against varroa mites is oxalic acid. Another organic substance, formic acid (sold as Mite Away Quick Strips® or Formic Pro®) and Apivar®, a synthetic miticide, were 2nd and 3rd, respectively.
The vast majority of 178 beekeepers surveyed used multiple miticides, a widely accepted practice to avoid developing resistance to one chemical. Many also used non-chemical procedures as part of an integrated pest management system.
Miticides are pesticides specifically designed to target mites but not honey bees.
Beekeepers also told us what methods they prefer for checking infestation levels and other information.
In this article we will provide the results of our poll.
What Are Varroa Mites?
Varroa destructor mites are parasites that attach themselves to honey bee brood and adult bees.
Varroa mites feed on the host leading to varroosis, a parasitic disease. Varroosis weakens the bee’s immune system making it more susceptible to other diseases and viruses. Varroa aid the spread of disease as they move around the colony.
Varroa mites are found in virtually all honey bee colonies and reproductive growth is exponential. Left unchecked, varroa mites and the viruses they spread will eventually cause a colony to collapse.
It is extremely difficult, if not impossible, to eradicate varroa from honey bee colonies. Most beekeepers work to control their population and limit the damage they cause.
The 2018 NYS Beekeeper Tech Team Report (available here) says that 61% of colonies sampled indicated a mite infestation level that requires “immediate treatment to prevent colony death”. It also says, “Varroa mite levels are a significant predictor of winter loss in New York State.” In the 2016 report, the survey sample indicated 90% of colonies had Varroa. The presence of Varroa is nearly universal among bee colonies.
Our article Varroa Mites: A Complete Treatment Guide provides much greater detail about the varroa destructor mite, methods of testing the level of infestation and various ways to mitigate its impact on your hives.
About Our Varroa Mite Treatment Poll
Varroa mitigation is a popular, and occasionally controversial, beekeeping topic.
A lot has been written on what beekeepers can or “should” do to mitigate varroa. We decided to ask beekeepers in a number of Facebook beekeeping groups to find out what they actually ARE DOING.
While we received 178 responses, this is not a scientific study.
Not surprisingly, respondents to our survey were overwhelmingly U.S. based. Canada and the UK were next and a number of other countries had one response.
The U.S. responses came from 37 states, led by Maine (10.2%) and New York (8.2%).
Respondents to our questions had a wide variety of beekeeping experience, both in terms of years beekeeping and number of hives managed.
Do Beekeepers Use Chemicals To Control Varroa Mites?
Properly used chemicals are very effective in controlling varroa populations. Treatments are administered in ways designed to kill the mites but not the bees. However, the bees may have other reactions (besides death) to the treatments.
I think every beekeeper would prefer to manage hives chemical-free. In fact, some beekeepers are resolutely “treatment-free” avoiding all chemicals and even some non-chemical interference in the business of their honey bees.
We did not put our survey in a Facebook treatment-free beekeeping group as any discussion of treatments is forbidden. Despite that, several respondents indicated that they do not use any chemicals to treat varroa mites.
See our article What Is Treatment-Free Beekeeping? (A Controversial Topic) for more information.
Nearly 90% of those surveyed said they use chemical treatments to control varroa mites. Only 10% do not use chemicals.
How Do Beekeepers Decided When To Treat For Varroa?
Beekeeping guides typically advise to chemically treat hives only when varroa mite infestation exceeds certain thresholds. Doing so limits to bees’ exposure to the chemicals and reduces chemical build up in wax and food stores, including honey.
However, the efficacy of many chemicals is affected by variables such as the temperature, existence of brood or if there is honey flow.
We have often treated our hives based on the calendar rather than mite counts because of these limitations. We wondered if we were alone.
We are clearly not alone.
Only 17.5% of respondents base their decision to treat for varroa solely on mite counts.
Over 82% use the calendar for at least some of their treatment decisions.
We suspect the primary driver of calendar treatments is the strong desire to treat just before winter. However, our survey did not address this question.
Treating New Bee Packages And Nucs
Newly purchased bees, particularly those from online suppliers, often come from large commercial bee operations and may have varroa mites. Even bees from reputable local beekeepers may arrive with some varroa.
I’ve seen recommendations to mist new bees with a mix of oxalic acid and sugar water prior to installing in the hive. We have never done that.
It turns out that a majority of respondents do not treat newly arrived bees as standard procedure. However, a significant minority do treat newly acquired bees.
How Do You Determine Mite Counts?
There are several ways to determine if your colony’s mite count exceeds acceptable thresholds:
- Visual inspection (not very reliable)
- Uncapping drone brood
- Sticky board
- Alcohol/Soap wash
- Powdered sugar roll
These methods are discussed in detail in our varroa mite treatment guide.
A sizable majority or respondents used either the alcohol/soap wash or the powdered sugar roll to count mites. These are considered the most reliable methods. However, many respondents indicated that they use multiple methods for monitoring mites (thus, numbers exceed 100%).
Mite Count Method
|Alcohol or soap wash||77.9%|
|Powdered sugar roll||15.6%|
|Uncapping drone brood to count||12.3%|
What Chemical Treatments Do You Use For Varroa Mites?
Beekeepers have a choice of synthetic and natural miticides.
Synthetic miticides are man-made compounds not ordinarily found in nature; natural ones use organic acids or essential oils.
Do not be lulled into a false sense of safety by the word “natural”. Some of these materials can be harmful if not used properly. For example, oxalic acid, while a naturally occurring substance, can be very harmful if you inhale the vapors. Use caution with all these products.
Oxalic acid and formic acid are two very effective organic compounds used as miticides.
Popular Varroa Mite Treatment Options
Common varroa mite treatments are compared in the table below. The information is intended as a general guideline. CAREFULLY READ ALL INSTRUCTIONS AND WARNINGS INCLUDED WITH EACH PRODUCT, ESPECIALLY REGARDING THE USE OF PROTECTIVE EQUIPMENT.
|Name||Active Ingredients||When to use||General Application Info||Length of Treatment||Temperature Restriction||Use during honey flow?|
|Apistan®||Fluvalinate||Spring and autumn||Strips hung in the brood chamber. Bees contact and transfer active ingredient.||6 weeks||Above 50°F (10°C)||No. Can add honey supers 2 weeks after treatment.|
|Apivar®||Amitraz||Spring and autumn||Strips hung in the brood chamber. Bees contact and transfer active ingredient.||42 - 56 days, not longer||None but bees should not be dormant.||No. Can add honey supers 2 weeks after treatment.|
|CheckMite+®||Coumaphos||Spring and autumn||Strips hung in the brood chamber. Bees contact and transfer active ingredient.||42 to 45 days, not longer||None but bees should not be dormant.||No. Can add honey supers 2 weeks after treatment.|
|ApiLife Var®||Thymol, eucalyptys oil, L-menthol||Early spring and after honey harvest||Tablet broken in 4 pieces, each place on top bars at the edge of the brood nest to fumigate the hive.||3 consecutive applications: 1st - 7 to 10 days; 2nd - 7 to 10 days; 3rd - 12 days||Between 64° and 95° F (18° and 35° C).||No. Add honey supers 30 days after treatment.|
|ApiGuard®||Thymol||Spring and autumn||Place open tray (which may require a spacer) in the hive to expose thymol gel. Bees contact gel and carry it through the hive.||2 consecutive treatments: 1st - 10 to days; 2nd - 2 to 4 weeks||Between 60° and 105°F (15° and 40°C). Avoid during nectar flows.||No. Manufacturer website is silent. Some forums indicate waiting 2 weeks.|
|Formic Pro®||Formic acid||Spring and autumn||Strips placed on top bars in brood boxes fumigate the hive with formic acid.||2 options: 14 day or 20 day||Between 50° and 85° F (10° and 29° C).||Yes.|
|Hop Guard II®||Hop compounds||Any time of year but best with less brood present||Hang strips over brood frame top bar so it hangs between frames.||30 days||Between 52° and 92° F (11° and 33° C).||Yes. Don't harvest wax and honey from brood boxes.|
|HopGuard 3®||Hop compounds||Any time of year but best with less brood present; follow with another miticide before overwintering||Hang strips between brood frames||14 days||Above 50°F (10°C)||Yes.|
|MiteAway Quick Strips®||Formic acid||Spring and autumn||Strips placed on top bars in brood boxes fumigate the hive with formic acid.||7 or 21 day treatment options||Between 50° and 85° F (10° and 29° C).||Yes.|
|Oxalic Acid||Oxalic acid dehydrate||Anytime there is no capped brood as it does not kill mites in cells||2 methods of treatment: dribble method mix of oxalic acid and light sugar syrup OR fumigation with a vaporizer.||3 consecutive weekly treatments recommeded||Between 35° and 55° F (2° and 13° C).||No.|
Treatments Used By Beekeepers
Virtually all respondents indicated the use of multiple chemical treatments. This is recommended practice to reduce varroa resistance to any one treatment. It is most likely driven by timing issues related to temperature and hive conditions. (And totals exceed 100%.)
|Product Name||Percentage Used|
|Oxalic acid - vaporization||78.1%|
|Oxalic acid - dribble||15.6%|
|MiteAway Quick Strips (Formic acid)||26.3%|
|Formic Pro (formic acid)||40.0%|
|Other formic acid||1.8%|
Which Miticide Is Most Or Least Effective In Controlling Varroa Mites?
Most noted selections
|Product Name||Most Effective||Least Effective|
|None stands out||22.5%||60.6%|
|Formic acid (various products)||16.3%||10.0%|
What Non-Chemical Methods Do You Use To Control Varroa Mites?
Chemical treatment is generally considered the most effective method of controlling varroa. However, beekeepers often use non-chemical methods as additional steps to reduce varroa numbers.
Varroa mites reproduce more effectively in drone brood’s larger cells. Many of these non-chemical procedures involve disrupting the growth of the drone population inhibiting varroa reproduction.
A high percentage of respondents indicated the use of screened bottom boards. It is possible that many of these beekeepers use screened bottom boards for reasons unrelated to varroa so I am not sure it’s a meaningful statistic.
This is another area where beekeepers may employ multiple tactics so totals exceed 100%.
Non-Chemical Methods Of Varroa Control
|Screened bottom boards||50.6%|
|Drone brood management||12.9%|
|Buy VSH bees||16.9%|
|Powdered sugar dusting||2.4%|
Varroa Mites And Winter Colony Losses
Honey bee colonies fail to survive winter for a variety of reasons, including:
- inadequate food (honey) supply to get through the season;
- insufficient population to keep the colony warm;
- excess condensation wetting the bees;
- predators; and,
- various diseases and pests, notably varroa mites.
Getting colonies through winter is one of the most important tasks in beekeeping. We asked beekeepers about their results over the past two winters.
The survival rate breakdown could have been more precise. While over half had a survival rate above 75%, a substantial number (24.2%) were below 50% survival. A large percentage attribute their survival rate significantly to varroa control.
Beekeeping advice includes a lot of information about what you can do and what you should do when it comes to varroa mites.
While our survey is not scientific, the responses from this diverse group seem to support the following opinions for monitoring and controlling varroa:
- Use an alcohol/soap wash or powdered sugar roll to assess mite counts;
- Try multiple methods of testing;
- It is okay to treat for mites based on timing issues;
- Vary the use of chemicals relying primarily on oxalic acid, formic acid and Apivar®;
- Some non-chemical treatments are worth pursuing in addition to chemical treatments.