How to Test for Varroa Mites: A US Beekeeper's Guide
The five reliable ways to test a beehive for varroa mites in the US: alcohol wash, sugar roll, CO2, sticky board and drone brood. Action thresholds, US treatments and a step-by-step guide.
Varroa mites are the number one reason US beekeepers lose colonies, and most of those losses are preventable. There are five reliable ways to check a hive for varroa: an alcohol wash, a sugar roll, the CO2 method, a sticky board (a passive 24 to 72 hour mite drop), and uncapping drone brood. The alcohol wash and CO2 kit give you the most accurate numbers, while the sugar roll, CO2 and sticky board all leave your bees alive. The constant across every method is the sample and the habit: pull about 300 bees (roughly half a cup), test at least monthly through the season, and act on what you find. This guide walks through each method, what the numbers mean, and when to test and treat through the US beekeeping year.
In this article
- Why varroa testing matters so much in the US
- The 5 testing methods compared
- How to do an alcohol wash
- How to do a sugar roll
- The CO2 method
- Using a sticky board
- Checking drone brood
- Why your mite count can spike
- When to test and treat through the season
- FAQ
Why does testing for varroa matter so much in the US?
Varroa destructor reached the United States in 1987 and spread to every state within about a decade. It is now the single biggest driver of honey bee colony loss in the country, and the heavy annual losses US beekeepers report each year are tied largely to the mite and the viruses it carries, especially Deformed Wing Virus. You cannot wipe varroa out of a colony, so the goal is not eradication. It is keeping the population low enough that your bees stay healthy, above all heading into winter.
Two things make monitoring non-negotiable here right now. First, our most relied-on chemistry is losing ground: amitraz, the active ingredient in Apivar and the most widely used synthetic miticide in the US, now shows documented resistance in several areas, with recent reports out of Southern California. Second, mites move between colonies far more than most beekeepers expect, so even a clean hive can be reinfested within weeks (more on that below). Guessing is not a strategy. The only way to know whether your levels are safe, whether a treatment actually worked, and when to switch to a different mode of action is to test, count and record. That habit is the backbone of integrated pest management.
The 5 varroa testing methods compared
Each method answers a slightly different question, and they trade accuracy for convenience. A wash or the CO2 kit gives you a hard number you can compare against a treatment threshold. A sticky board or a quick look at drone brood tells you mites are present and roughly how fast they are building. Most US beekeepers run a wash or CO2 test for their real count and use the passive checks in between.
| Method | Bees survive? | Accuracy | Time | Best for |
|---|---|---|---|---|
| Alcohol wash | No | Highest | ~5 min | Your most accurate count |
| Sugar roll | Yes | Good | ~5 min | A count without losing bees |
| CO2 | Yes | High | ~2 min | Fast, repeatable, no mess |
| Sticky board | Yes | Rough guide | 24 to 72 hrs | Passive, no bee handling |
| Drone uncapping | No (drone brood) | Presence only | ~5 min | Spotting mites early |
How do I do an alcohol or soapy water wash for varroa?
The alcohol wash is the method the USDA and university bee labs lean on, because it dislodges the most mites and gives the most reliable count. Wash the same sample three times and you will free well over 90 percent of the mites riding on those bees, against roughly 70 percent from a single wash. The downside is that the sampled bees do not survive, but 300 bees is a tiny fraction of a colony of tens of thousands. If you would rather not use alcohol, a soapy water wash works the exact same way for a few cents.
What you can use
Alcohol: isopropyl (rubbing) alcohol or denatured alcohol at around 70 percent, enough to cover the bees, roughly 3 to 5 fl oz (about half a cup).
Soapy water: water with a little dish soap, about one tablespoon per half gallon of water. The soap breaks the surface tension so the mites let go and sink. Use a low-suds dish soap, because a head of bubbles makes the mites much harder to see and count.
Whichever liquid you pick, the job is the same: loosen the mites so they fall off the bees and gather in the bottom of the jar where you can count them.
Step by step
- Fill the kit. Pour in about half a cup of alcohol or soapy water, enough to cover the basket in the base.
- Find the queen, then pick your frame. Use a frame of capped brood and make sure the queen is not on it. The young nurse bees clustered over the brood carry the most mites, so they are the sample you want.
- Collect about 300 bees (half a cup). Roll the open jar down the face of the frame so bees tumble in, or shake the frame into a tub and scoop half a cup.
- Cap it and shake for 60 seconds. Shake firmly so every mite is knocked loose.
- Strain and count. The mites drop through into the lower chamber. For a true count, run the wash on the same bees two more times.
- Do the math. Divide your total mite count by three to get mites per 100 bees.
Note: test liquids are not included with the kit.
A simple jar kit that handles both the alcohol wash and the sugar roll. The easiest way to start putting a number on your mites.
Prefer to watch it done first? This Honey Bee Health Coalition demonstration starts at the alcohol wash, the same jar-and-screen method your kit uses (the powdered sugar roll is shown earlier in the clip).
Video: Honey Bee Health Coalition.
How do I do a sugar roll instead?
The sugar roll is the answer for beekeepers who do not want to sacrifice bees at every check. You coat the same 300-bee sample in powdered (confectioners) sugar, which coats the mites and makes them lose their footing so they tumble off when shaken. It reads a little lower than an alcohol wash and is more sensitive to your technique, but as a routine, bee-friendly check it is hard to argue with, and the same Varroa Mite Test Kit does it.
- Collect 300 bees exactly as you would for the alcohol wash, queen kept safely out of the sample.
- Add a heaping tablespoon of powdered sugar, roll the bees until they are evenly dusted, and let them sit a minute or two.
- Shake the sugar out through the mesh onto white paper or into a tub of water, where the mites stand out against the sugar or float to the top to be counted.
- Return the bees at the hive entrance and divide your count by three for mites per 100 bees.
Skip the sugar roll in humid weather or during a heavy nectar flow, when damp sugar clumps on the bees and ruins the sample.
The same jar does both tests: a gentle sugar roll when you want to keep the bees, or an alcohol or soapy water wash when you want the most accurate count.
What is the CO2 method, and is it better?
The CO2 method is the quickest way to get a real number while keeping every bee. A short burst of CO2 briefly stuns the bees and the mites, you shake the sample so the mites fall into a clear chamber to count, and the bees come around and go back in the hive within about 20 to 30 seconds. No alcohol to carry or dispose of, no mess, and the device is reusable, so your only running cost is the CO2 itself. If you test often or work through a row of hives in one session, it is tough to beat.
- Scoop about 300 bees into the sampling chamber.
- Give a short burst of CO2 to immobilize them.
- Shake to release the mites, then count them in the clear chamber.
- Tip the bees back into the hive once they wake up.
An accurate count with no alcohol and no losses. Includes the CO2 application tool, metal nozzle and sampling container (CO2 canisters not included).
How do I use a sticky board for a 24-hour mite drop?
A sticky board is the lowest-effort check there is, because you never touch a bee. It rides in the tray of a screened (mesh) bottom board and catches the mites that groom off and fall through the mesh. It will not hand you a precise infestation rate like a wash does, but a climbing daily drop is an early warning that your numbers are rising and a real count is due.
- Slide the mat into the drawer under your screened bottom board and peel the cover back to expose the sticky side.
- Leave it 24 to 72 hours.
- Count the dropped mites against the printed grid and note the figure per day so you can watch the trend.
You will need a screened bottom board with a drawer for this. If you are still on a solid floor, our mesh vented base with drawer trap is built for exactly this, and it improves hive ventilation as a bonus.
Disposable sticky sheets printed with a counting grid. Drop one under a screened bottom board and read the daily mite fall at a glance.
How do I check drone brood for varroa?
Worth knowing: most of a colony's mites are not on the adult bees at all. At the peak of the season the bulk of varroa are sealed inside capped brood, and they favor drone cells because drones take longer to develop, giving the mites more time to breed. That is the blind spot a wash cannot see, which is what makes drone brood such a useful early warning.
Run a capping fork or scratcher through a patch of capped drone brood, lift out a clump of pupae, and look for the reddish-brown mites standing out against the pale bodies. This tells you whether mites are present, not your overall load, so use it alongside a wash or CO2 test rather than in place of one.
To make it routine, set a drone foundation frame at the edge of the brood nest. The larger drone cells draw the queen to lay drones in one spot, giving you a dedicated frame to check. It doubles as a chemical-free control: once the brood is capped, pull the frame and freeze it to kill the mites inside, then put it back for the bees to clean out and start over.
Deep pink foundation with larger drone cells that concentrate drone brood in one frame, so you can check and trap mites in a single spot.
Why your mite count can spike: reinvasion
Even when your own count looks low, it can jump within weeks, and reinvasion is usually why. When an untreated colony nearby collapses, its mites do not die with it. They climb onto robbing bees that carry them straight into healthy hives, and beekeepers call the result a mite bomb. Drifting bees do the same on a smaller scale in a tightly packed apiary, and operations that haul colonies to pollination sites, such as the California almonds, mix bees and mites from all over the country in one place.
The practical lesson is simple: do not test once and assume you are covered for the year. A low reading in June tells you nothing about August. Test on a regular schedule, treat when you cross your threshold, and trust the trend over any single number.
When should I test, and when do I treat?
Test at least once a month through the active season, and more often in late summer and fall when mite numbers build fastest. That late-season stretch is the one that decides winter survival, because the mites you miss in August and September are the ones that damage the long-lived winter bees your colony needs to make it to spring.
On thresholds, US guidance has trended lower over the years as the viruses varroa spreads have grown more damaging. The Honey Bee Health Coalition commonly cites 3 mites per 100 bees (3 percent, about 9 mites in a 300-bee sample) as an action point, while the University of Minnesota Bee Lab suggests holding levels under 2 percent and treating once you reach 2 mites per 100 bees (6 in a 300-bee sample). Since a sample of adult bees can undercount mites hidden under brood cappings, the lower number is the safer target.
A simple way to picture the season:
- Spring: knock mites down early so they do not snowball over summer. Many beekeepers treat packages and overwintered colonies before honey supers go on.
- Summer: monitor monthly and treat if you cross your threshold, choosing a product that is safe to use with honey supers on if there is honey on the hive.
- Late summer: the most important treatment of the year, timed before and into September to protect the winter bees.
- Late fall: a broodless-period clean-up, such as oxalic acid when the cluster has little or no brood, removes the mites that would otherwise overwinter.
When you treat, the US has several EPA-registered options, including amitraz (Apivar), formic acid (Formic Pro), thymol (Apiguard, ApiLife VAR), oxalic acid (Api-Bioxal, applied as a dribble or vapor) and hops beta acids (HopGuard). Rotate active ingredients so the mites do not build resistance, mind the temperature and honey-super rules on each label, and always follow the label. For the current registered products see the EPA list of approved varroa products and the Honey Bee Health Coalition's Varroa Management Guide.
Frequently asked questions
Can I test for varroa without killing my bees?
Yes. The sugar roll, the CO2 method and the sticky board all leave your bees alive. The CO2 kit is the most accurate of the three, the sugar roll is the cheapest, and the sticky board needs no bee handling at all. The alcohol wash is the most reliable test overall, but it costs you the 300-bee sample.
How many bees do I need for a varroa test?
About 300, which is roughly half a cup. Using the same sample size every time is what lets you compare results month to month, so consistency matters. Take them from a brood frame, after checking the queen is not on it, because the nurse bees there carry the most mites.
Is the alcohol wash or sugar roll more accurate?
The alcohol wash. Three washes recover well over 90 percent of the mites on your sample, while a sugar roll recovers a little less and is more affected by humidity and technique. Both are valid; choose the wash for the most reliable number and the sugar roll when you would rather keep the bees.
Why check drone brood if I already do a wash?
Because a wash only sees the mites on adult bees, and a large share of the colony's mites are sealed inside capped brood, especially drone cells. Uncapping a patch of drone brood is a fast way to catch an infestation a wash might underplay early in the season.
When should I treat through the season?
Treat whenever you cross your threshold, but build the year around two key windows: a spring knock-down before supers go on, and the late-summer treatment that protects your winter bees. A broodless oxalic acid treatment in late fall cleans up the rest. Always rotate active ingredients and follow the product label.
Do I have to report varroa if I find it?
No. Varroa has been established and endemic across the United States since 1987, so unlike places where it is a new arrival, there is no requirement to report it. You manage it as part of routine beekeeping. Some states do run apiary registration or inspection programs, so it is worth checking your state's apiary program or extension service for local rules and advice. (This reflects the situation at the time of writing.)
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Shop varroa testing tools →This article is general information for US beekeepers and is not a substitute for current guidance from your state apiary program or extension service. Always follow product labels and EPA registration conditions when treating for varroa.