Updated on March 12th, 2021
Varroa mites are a nearly universal threat to the survival of your beehives. Some beekeepers try to operate without the use of chemicals (“treatment-free”). However, many use miticides designed to kill mites, but not bees, for varroa mitigation.
With at least ten miticides available (and some with multiple delivery systems), how do you choose the best one to use?
Varroa mite treatments have limitations (temperature, brood, population, and honey flow), and should be varied to avoid resistance. Choosing the best miticide requires a decision tree based on circumstances. Using our tree below, formic and oxalic acids are best for full season coverage.
However, opinions vary. In this article, we will discuss varroa mites and lay out the the treatment options both synthetic and organic.
At the end of this article, you can find our “decision tree” chart. On this chart you can narrow down your treatment options quickly based on the factors we describe.
If you are more interested in treatment-free beekeeping, see our article What Is Treatment-Free Beekeeping (A Controversial Topic).
Varroa Destructor Mites
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.
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.
Once infecting a hive, varroa mite populations grow exponentially, creating a severe threat to the colony’s survival. The following short video explains how.
When To Treat For Varroa Mites
To select the best treatment for varroa mites, you need first to determine when to treat them.
In determining when to treat hives for varroa mites, beekeepers rely on two primary methods: testing the hive’s level of infestation (mite counts) or only by the calendar.
Included in the calendar method, I would add routine treatment of new bee packages and nucs upon arrival.
We recently polled 178 beekeepers and found that in determining when to treat:
- About 42% of beekeepers treat new bees routinely;
- Only 17.5% of respondents relied solely on mite counts;
- Over 82% used some combination of mite counts and calendar.
See our article Comparing Varroa Mite Treatments (What Beekeepers Use) for more details about our poll.
Visual inspection of a hive for mite infestation is hugely unreliable. Instead, you can perform mite counts by:
- Uncapping drone brood;
- Using a sticky board;
- Alcohol/soap wash; or,
- Powdered sugar roll.
Uncapping Drone Brood
Mites favor large drone brood cells for propagating. Uncap at least 100 drone cells from various frames in the hive and remove the brood.
Mites will be clearly visible against the white drone pupa. Also, look for Varroa remaining in the empty cells.
Generally, a 5% or less count in the drone brood is considered a low to moderate infestation level. If your count is 20-25%, it’s a heavy infestation, and you should consider immediate steps to mitigate it.
A sticky board is a non-absorbent sheet (preferably white) placed on the bottom board. Coated with a thin layer of petroleum jelly or shortening (hence, sticky), it traps any mites that drop to the bottom of the hive. Using preprinted sheets with grid lines makes counting easier.
Three days after inserting the board, remove it and count the number of mites. Divide the number of mites by 3 to get an average daily mite drop count.
The size of your hive is an essential factor in assessing a sticky board mite count. A count of 30 – 40 per day for a “standard” hive of 2 deeps and a couple of supers would indicate the need for mitigation.
Alcohol/Soap Wash Or Powdered Sugar Roll
An alcohol/soap wash or powdered sugar roll is the most reliable mite count method and are similar in execution. Both ways require that you use about a ½ cup of bees from a brood frame. BE CAREFUL NOT TO TAKE THE QUEEN.
Place the ½ cup of bees (about 300 bees) in a container with an alcohol or soap solution or powdered sugar. These mixtures help separate the mites from the bees for a count.
Read our article Varroa Mites: A Complete Treatment Guide for detailed step-by-step instructions on how to perform the alcohol/soap wash and powdered sugar roll.
Generally, a mite count of 1% – 2% is acceptable. Mite counts between 2% and 3% suggest that you may want to take steps before the situation worsens. Greater than 3% indicates a high risk to your colony.
Miticides can be less effective depending on the level of brood in the hive and ambient temperatures. Avoid certain miticides when honey supers are in place because of the potential for contaminating the honey.
Hence, beekeepers often rely on the calendar and treat hives at certain timing intervals or based on the hive conditions.
For example, some miticides are less effective above certain temperatures. A beekeeper may opt to treat a colony before climate conditions preclude the use of a particular chemical.
Late fall, after the drones have been evicted from the hive (yes, the boys get kicked to the curb) and there are no brood or honey supers, is an ideal time to treat the bees before winter arrives.
In spring, new bees arrive and may be treated before installing them in a hive.
New Bee Packages And Nucs
Whether you purchase bees from a reputable local beekeeper or a large online supplier, your new package may arrive with a few unwanted mites hitching a ride. As we noted, most beekeepers do not routinely treat new packages though a substantial minority does.
Although miticides are designed not to kill bees, some can still be harsh on the colony. If you opt to treat new bees, we recommend using a mixture of sugar syrup and oxalic acid, an organic chemical.
You will be wetting the bees with this mixture, so I would only do it if it is at least 45° F (10° C), though I’ve read that you can use this method at lower temperatures.
Note: Do not be fooled by a chemical being labeled “organic.” Some of these materials can be harmful if not used properly. For example, while naturally occurring, oxalic acid can be hazardous if you inhale the vapors. Use caution with all these products.
The same oxalic acid mixture is used for both packages and nucs, but the application process varies.
Wear goggles, a respirator, and chemical resistant gloves when you work with oxalic acid (remember what we said about organic chemicals).
In a glass container, mix:
- 1.2 oz (35 g) of oxalic acid dihydrate, and
- 34 oz (1 liter) of 1:1 warm sugar water (thin syrup – see Why, What, How & When To Feed Honey Bees for instructions).
Note: Do not store any unused oxalic/syrup mixture. Dilute the excess mixture with lots of water dispose of it down the drain.
Bees in new packages are in a confined space and tightly clustered.
First, spray the bees from all sides with ONLY plain thin syrup. Give the bees about 2 hours to gorge on this syrup.
Next, spray the oxalic/sugar syrup mixture evenly on all sides of the package. Use approximately five teaspoons for a 3 lb. package (about 10,000 bees).
Then wait three days before installing these bees in a hive. During that time, keep the bees in a safe, cool, dark location.
There are several drawbacks to treating a new bee package:
- Building comb takes time, and you want your bees starting as soon as possible. Losing three days is not ideal. If you have comb available from other hives, this may not be an issue.
- You need to keep your bees well fed on sugar syrup during the 3-day waiting period.
- The bees could be at risk of overheating in warm weather.
As a mini hive, your nuc will have bees spread among up to 5 frames, not clustered like a package. Transfer them to the new your hive keeping the nuc frames in the center to apply the same oxalic acid/syrup mixture described above using the “dribble method.”
Have your bee smoker ready.
Fill a 60 ml plastic syringe (available here on Amazon) to the 50 ml line. (Remember to wear protective goggles, respirator, and gloves).
Puff a little smoke on top of the frames, driving most of the bees down into the nuc.
Then, dribble 5 ml of the oxalic mix evenly along the open seam between each frame. (You may want to practice using plain water – outside the nuc). Only one pass for each seam.
There is a significant disadvantage to this treatment of a nuc. Oxalic acid does not kill any mites that may be in the brood as some other treatments will. However, we think it is the best option for bees in this early stage.
Selecting The Best Varroa Mite Treatment
After deciding to treat for Varroa in an established colony, whether based on mite counts or otherwise, you need to select a miticide.
Common varroa mite treatments are compared in the table below. The information is only a general guideline. CAREFULLY READ ALL INSTRUCTIONS AND WARNINGS INCLUDED WITH EACH PRODUCT, ESPECIALLY REGARDING THE USE OF PROTECTIVE EQUIPMENT.
As you look through the table, you will notice that many chemicals have temperature restrictions, some should not be used with honey supers on.
After using certain miticides, there is a waiting period before adding supers.
|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.|
NOTE: Product names link to the manufacturer’s or distributor’s website for more detailed information except for oxalic acid (a generic product), which links to a Honey Bee Health Coalition video.
In the decision tree chart below, we’ve attempted to make this selection process a bit easier to follow. Answer a few questions and follow the arrows to the options that selected. There you can see the temperature and other restrictions to further narrow your choices.
Whatever you select, follow all safety instructions for any miticide, which may include, among other things:
- Wear chemical or acid-resistant gloves;
- Use protective eye gear;
- Avoid inhaling fumes (best done by wearing a mask approved for your application);
- Avoid contact with your eyes, skin, or clothing;
- Wash up thoroughly after using miticides; and,
- Store and dispose of any chemicals properly.
Check whether a product is approved for use at your location. For example, as of this writing:
ApiLife Var is not registered in CA, AK, and DC per the Veto-pharma website.
Varroa Mite Treatment Decision Tree by jhoward573
Do not use the same treatment every time. Vary treatment to reduce the possibility of Varroa resistance to that treatment.
Remove synthetic chemicals per the manufacturer instructions also to avoid resistance.