Varroa monitoring basics for small apiaries

Varroa monitoring is the difference between wintering bees and watching them fall apart in late summer. If you keep 0–50 hives in a temperate or cold climate, varroa monitoring needs to be a routine, not a panic move after you see deformed wings.

Varroa doesn’t just “weaken bees.” It builds quietly, spreads between colonies through drifting and robbing, and stacks the deck for virus problems right when you need healthy winter bees.

Varroa monitoring: why it matters more than treatments

Treatments are tools. Varroa monitoring is steering.

Without mite counts, most small beekeepers fall into one of two traps:

Treating on a calendar and missing the real spike (often mid to late summer).
Treating too late because the colony “looked strong” in June.

A strong-looking colony can still be raising virus-loaded brood if mite pressure is climbing. By the time you see crawling bees, patchy brood, or lots of bees drifting into other hives, you are already behind.

Monitoring also helps with a problem many hobby beekeepers don’t expect: mite reinfestation. Your own treatment can work, then mites pour back in from collapsing colonies nearby. Regular checks catch that early.

Here’s the practical goal: get repeatable numbers you trust, at the times of year that matter most.

Alcohol wash: the most reliable field method

If you want one method that gives you a dependable “yes or no” for treatment decisions, do an alcohol wash (or a soapy water wash). It’s widely recommended because it’s consistent and accurate.

Yes, you kill a sample of bees. It’s still the best trade most of the time. In a healthy summer colony with 20,000–40,000 workers, sacrificing about 300 bees is a small price to avoid losing the whole hive later.

What you need

A mite wash cup or a jar setup with a screen (commercial “mite washer” cups make life easier)
70%–91% isopropyl alcohol, or soapy water
A 1/2 cup measure (roughly equals 300 bees)
A white tray or bucket to count mites against
A marker and a notebook (or your phone)

How to take a good sample

Go to the brood nest. You want nurse bees, because that’s where mites concentrate.
Find the queen or work carefully to avoid her. I like to spot her first when I can, then sample from another brood frame.
Shake bees off a brood frame into a tub or directly into your sampling container.
Measure about 1/2 cup of bees (about 300). With practice you’ll get fast and consistent.
Add alcohol/soapy water, seal, and shake hard for the recommended time for your device (usually 30–60 seconds of vigorous shaking).
Drain through the screen and count mites in the liquid against a white background. Rinse and drain again if your device calls for it.

Common mistakes I see (and how to avoid them)

Sampling from honey supers or outer frames. That gives you a “feel-good” low count that can be totally wrong.
Not shaking enough. Be consistent. If you barely agitate the sample, you undercount.
Sampling one hive and assuming the rest match. In small apiaries, colonies can vary a lot. One booming hive and one marginal hive can sit side by side with very different mite loads.

Turning the count into an infestation percentage

If you use a 300-bee sample, the math is simple:

Mites counted ÷ 3 = mites per 100 bees (percent).

Example: 9 mites in a 300-bee wash is about 3 mites/100 bees, or 3%.

That’s a number you can compare month to month, and year to year.

Sugar roll: useful when you don’t want to sacrifice bees

The sugar roll (also called powdered sugar shake) is popular because you can return the bees to the hive. The workflow is similar: collect about 300 bees from a brood frame, coat them with powdered sugar, shake mites loose, and count what falls out.

It can work, but you need to understand its weak spots.

When sugar roll makes sense

You’re working a very small nucleus colony and you truly don’t want to reduce the population.
You’re doing frequent checks and want a quick trend line.
You’re teaching or demonstrating and want a non-lethal method.

Where sugar roll can mislead you

Research and field experience keep pointing to the same issue: sugar methods can undercount or vary more than alcohol washes, especially if your technique is inconsistent. Humidity, sugar clumping, shaking time, and screen setup all matter.

My rule: if a sugar roll puts you anywhere near a treatment threshold, confirm with an alcohol wash on the next inspection. It’s better to be slightly “too careful” than to head into winter bee production with a mite problem you talked yourself out of.

Sugar roll tips that improve consistency

Use dry, fine powdered sugar (lumpy sugar gives lumpy results).
Keep your shaking time consistent every time.
Don’t rush the sample collection. Still pull from the brood area, and still avoid the queen.
Clean and dry your screen between colonies so old sugar and wax bits don’t block mite drop.

CO₂ injection and sticky boards: quick checks, with limits

There are a couple of methods you’ll see mentioned that are worth knowing about, but I treat them as supporting players, not the star.

CO₂ mite testers

CO₂ systems anesthetize the bees so mites drop off and can be counted. They can be fast, and some commercial kits combine alcohol wash, sugar roll, and CO₂ options.

The downside is practical: extra equipment, gas cartridges, and one more thing to fiddle with when your hands are already sticky and gloved. If you already own a CO₂ tester and you get consistent results, fine. If you don’t, I would put your money toward a good wash cup and keep it simple.

Sticky boards (monitoring boards)

Sticky boards under a screened bottom board can tell you if mites are present and whether mite drop is increasing. They are also useful when weather makes opening hives a bad idea.

But boards measure natural mite fall, not infestation percentage. That makes them harder to interpret, especially across different colony sizes and brood levels. Many beekeepers use them as a trend check, then confirm with an alcohol wash when it matters.

If you like boards, use them like this:

Put the board in for a consistent period (often 24–72 hours).
Track changes over time in the same colony.
Don’t use board counts alone to decide you’re “safe” for the season.

How often to do varroa monitoring in a hobby apiary

For temperate and cold climates, the critical window is usually mid-summer through early fall, because that’s when mite populations can surge and when your winter bees are being raised.

A solid baseline plan is:

At least 4 times per year (spring, early summer, mid-summer, late summer/early fall).
Monthly checks during the active season if you can manage it, especially once nectar flow slows and robbing pressure rises.

A practical schedule that fits 0–50 hives

Adjust the months to your local climate, but the pattern holds.

Early spring (first reliable brood expansion): baseline check.
After spring honey removal or when you add summer supers: check again.
Mid-summer: this is where many “surprise” collapses are born.
Late summer to early fall: the winter-bee protection check.
Post-treatment (10–14 days after finishing, depending on product): verify the drop worked and watch for reinfestation.

Mississippi State Extension specifically calls out sampling by early July (after spring harvest) so there’s time to respond before winter bees are produced. That timing logic applies even more in colder climates where winter comes early.

How many colonies to sample?

If you have fewer than 10 colonies, sampling every colony is realistic and removes guesswork. For larger apiaries, sampling a subset can work if you do it consistently and don’t always pick your “favorite” hives. The Honey Bee Health Coalition guide suggests sampling each colony under 10, and sampling a minimum set in larger yards.

My field approach:

1–5 hives: sample every hive.
6–20 hives: sample at least half, rotating so every colony gets tested regularly.
20–50 hives: sample 10–20% each round, plus any colonies that look off (weak, queenless history, heavy robbing, late splits).

If you want a repeatable routine, keep a simple yard log and pair your mite checks with a standard inspection flow. A checklist helps when you’re tired or working alone, and it keeps you from “forgetting the boring stuff.” Use a consistent inspection template like the ones in the inspection checklists.

Making sense of your mite count

Numbers matter because varroa management is about acting early enough. Different regions publish slightly different thresholds, but many recommendations cluster around 2–3 mites per 100 bees (2–3%) as the zone where you should be planning treatment, especially through the main season.

Ontario’s guidance is a good example of seasonal tightening: treat in May if alcohol wash is above 2 mites/100 bees, and in August above 3 mites/100 bees.

I like a simple three-zone interpretation for small-scale beekeepers:

Low zone (green)

Spring/early season: under ~2% (under 6 mites in a 300-bee wash)
Mid to late season: under ~3% (under 9 mites in a 300-bee wash)

In the low zone, keep monitoring and don’t get complacent. If you’re splitting a lot, robbing is heavy, or you’re surrounded by unmanaged colonies, I tighten my schedule.

Medium zone (yellow)

Around 2–3% depending on season and local guidance

This is where you make a plan now. Don’t wait a month and hope. In cold climates, the calendar moves fast and the “winter bee window” is shorter.

In the yellow zone I ask two questions:

What will mite pressure look like in 4–6 weeks if I do nothing?
When is my next management constraint (honey supers on, travel, weather)?

Most hobby beekeepers get burned because they wait until they have time. Mites don’t care about your schedule.

High zone (red)

Clearly above threshold, often 4–5% and higher (12–15+ mites in a 300-bee wash)

Now you’re not choosing between treatments. You’re choosing between saving the colony and losing it, and you’re doing it under time pressure.

At higher levels, colonies are at serious risk, and even if you knock mites back later, the damage to the bee population and virus load may already be done.

One more nuance: method matters

Alcohol wash counts tend to be more dependable for decision-making than sugar roll counts. If you’re using sugar, treat “medium zone” as “confirm now.”

Tools that make monitoring plans easier

A good varroa monitoring habit is mostly about removing friction. When you already know which hives you’ll sample, when you’ll sample, and what number triggers action, you stop procrastinating.

If you want help turning your yard size and season timing into a simple plan, build it in the Varroa Strategy Planner.
If you’re trying to standardize how you work the yard (especially if you have family members helping), start from the broader beekeeping tools section and pick one routine to stick with.

If you also keep a running note in your yard log like “6 mites, 300 bees, June 12, hive 4,” you’ll be shocked how quickly patterns show up.

Pick one reliable method, put it on a schedule, and treat your mite count like any other livestock metric. Do your next round of varroa monitoring this week, then use the Varroa Strategy Planner to lock in the dates for the rest of your season.