Take roughly 300 adult bees from one to three brood-nest combs, avoiding the queen, and do an alcohol or soap wash. That's about half a cup of bees, lightly packed. The Honey Bee Health Coalition's Tools for Varroa Management guide is blunt that using fewer than 300 bees will not give you an accurate sample.
Why the alcohol wash and not something gentler?
Because it's the one that gives you a number you can act on. The Coalition's guide rates the alcohol or soap wash as the most reliable method, the powdered sugar shake as reliable but more prone to error, and sticky boards under "less reliable" — useful for tracking trends or a quick post-treatment check, but hard to interpret as a per-bee measure.
Yes, the sample bees die. Three hundred bees is a rounding error against a colony of forty thousand, and the alternative is guessing.
Step by step
- Find a frame of open brood from the middle of the nest. Check the queen isn't on it.
- Shake the bees into a tub, then scoop about half a cup into your wash jar.
- Cover with alcohol (windshield washer fluid works) or a soap solution.
- Shake hard for a full minute. Longer than feels necessary.
- Pour through the screen and count the mites in the liquid.
- Divide by 300, multiply by 100. That's your percentage.
What number should worry me?
The Ninth Edition of the Coalition guide sets thresholds by colony phase, not calendar season. From Table 1: Dormant, treat at 1% or above; Population Increase, 1% or above; Peak Population, 2% or above; Population Decrease, 2% or above.
You'll see "1% in fall" repeated online. That's a mistranslation. Fall is the Population Decrease phase, and that's 2%. The 1% figure belongs to Dormant phase, sampled just before the bees cluster.
How many colonies do I need to sample?
Per the guide: under ten colonies, sample every one. Larger apiaries, a minimum of eight randomly selected colonies or at least 10 percent of the total, mixing hives from the centre and the edges of the yard and of varying strength.
And the line worth remembering if you run multiple yards: if you cannot sample every colony in an apiary, treat the whole yard if any colony exceeds the threshold.
How often should I be doing this?
Enough that a number never surprises you. Spring before supers, again when supers come off, and again before the bees cluster is a reasonable minimum. In July you're establishing where you stand before the decisions that matter in August.
What if I treat — do I test again?
Always. The guide says post-treatment results should come back under 2%. A treatment that failed and a treatment you never did look identical from the outside, and only a wash tells you which one you had.
Questions about any of this? Call or text us at (701) 809-0153. We're always happy to help, even if you didn't get your bees from us.