How to Test Your Bees for Varroa Mites (A Beginner's Step-by-Step)

If there's one skill every new beekeeper should learn in their first season, it's how to count mites. Varroa mites are the single biggest threat to honey bees, and the tricky part is that a colony can look busy and healthy right up until it isn't. By the time you can see mites riding on bees or bees with crumpled wings, the infestation is usually serious. (They're a big part of the story in Colony Collapse Explained: Why Bees Are in Trouble.)

The only way to know is to test. It takes about ten minutes, and it's much less intimidating than it sounds.

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Why mites matter so much

Varroa mites feed on developing and adult bees and spread viruses through the colony, including one that causes deformed wings. Mite populations grow quickly while the colony is raising brood, and they tend to peak in late summer and fall, right when the colony is raising the long-lived winter bees that need to carry it to spring.

Three ways to count

• Alcohol wash: the most accurate method most backyard beekeepers can do. It does sacrifice the bees in the sample, roughly 300 of them. That sounds like a lot, but it's a tiny fraction of a colony, and the information can save the whole hive.
• Sugar roll: slightly less accurate, but the bees survive and go back into the hive.
• Sticky board: a board under a screened bottom that catches falling mites. Useful for trends, but the least reliable for decisions.

Whichever you choose, testing is always better than not testing.

What you'll need

• A mite-testing jar or shaker kit with a mesh lid (widely sold, or make your own with a mason jar and hardware cloth)
• A half-cup measuring cup
• A plastic tub or dishpan
• 70% rubbing alcohol (or windshield washer fluid) for a wash, or powdered sugar for a roll
• A white plate or tray for counting

Step by step

1. Pick the right frame. Choose a frame with open (uncapped) brood. Nurse bees on these frames carry the most mites, so your sample will be the most accurate.
2. Find the queen, or at least make sure she's not on it. This is the most important step. Check both sides of the frame carefully before you go further.
3. Shake the bees into the tub. Give the frame one firm downward shake over the tub.
4. Scoop half a cup. Tip the tub so bees gather in a corner, then scoop a level half cup, which is about 300 bees. Pour them into your jar right away.
5. For an alcohol wash: add enough alcohol to cover the bees, close the lid, and swirl gently for about a minute. Pour the liquid through the mesh onto your white plate.
6. For a sugar roll: add a couple of tablespoons of powdered sugar, roll the jar for a minute or two so every bee is coated, let it rest a minute, then shake the sugar out through the mesh onto your plate. A light mist of water makes the mites easier to see. Release the bees back into the hive.
7. Count the mites, which look like tiny reddish-brown ovals.
8. Divide by 3. That gives you mites per 100 bees. For example, 6 mites in your sample means 2 mites per 100 bees, or 2%.

Nervous about opening the hive? These tips on calming your bees during inspections help.

What your number means

The Honey Bee Health Coalition, whose varroa guide is the go-to reference for North American beekeepers, recommends treating at about 1% when the colony is growing in spring, and about 2% during the summer peak and fall decline. Treat those numbers as a ceiling, not a target. It is much easier to keep mites low than to bring them down once they've taken off.

How often to test

Aim for roughly once a month from early spring through fall, plus a test before any treatment and another about two weeks after to confirm the treatment worked. Write down every result. One number is a snapshot. The trend over the season tells you whether you're staying ahead.

Our Apiary Management Journal is a handy place to keep your counts.

If your count is high

There are several kinds of mite treatments, including organic acid products, thyme-oil-based products, and synthetic options. Each one has its own rules about temperature, whether brood is present, and whether honey supers can be on the hive. The most important rule: use only products registered for honey bees, and follow the label exactly. The Honey Bee Health Coalition's free Tools for Varroa Management guide compares the options, and your local beekeeping club can tell you what works well in your area.

The takeaway

Testing for mites isn't the fun part of beekeeping, but it's the part that keeps your bees alive. Ten minutes a month is a small price for a colony that makes it through winter. (Skipping it is one of the most common beginner beekeeping mistakes.)

Heading into fall? See how mite testing fits into the rest of the season in Fall Hive Prep in the Bay Area.