Sugar Roll or Alcohol Wash: Step-by-Step Varroa Sampling Protocols Compared
A practical, side-by-side walkthrough of the two standard adult-bee sampling methods for Varroa mite counts, including exact steps, sample sizes, and when to choose one over the other.
Why sampling method matters as much as frequency
Regular Varroa monitoring is only useful if the number it produces is reliable enough to act on, and the two standard adult-bee sampling methods, sugar roll and alcohol wash, differ meaningfully in accuracy despite testing the same underlying question: how many mites are riding on a sample of roughly 300 nurse bees. Choosing between them is less about which is universally better and more about matching the method to the situation, since one kills the sample bees and the other does not.
Both methods work by dislodging phoretic mites, the mites currently riding on adult bees rather than sealed in brood cells, using either a coating agent (powdered sugar) or a liquid (alcohol or, less commonly, dish soap solution) to make the mites lose their grip and separate from the bees during agitation. Mites in capped brood are not sampled by either method, which means both readings understate total colony mite load to some degree, particularly earlier in the season when more of the population is still in brood.
Alcohol wash, step by step
Shake roughly 300 bees (about a half cup by volume) from a frame containing open brood, since nurse bees near brood tend to carry higher, more representative phoretic mite loads than foragers, into a wide-mouthed jar. Add enough alcohol (isopropyl alcohol or windshield washer fluid without dye works, though dedicated bee-safe wash solutions are available) to fully submerge the bees.
Shake the jar vigorously for a full minute; this is the step most commonly rushed, and shortened agitation is one of the more common sources of undercounting. Pour the liquid through a mesh or screen fine enough to catch mites but let liquid pass, into a light-coloured container or tray, and count the mites caught on the screen. Divide the mite count by the number of bees sampled and multiply by 100 to get mites per 100 bees, the standard unit used for comparing against treatment thresholds.
The bees in this method do not survive, which is the main drawback; the trade-off is a reliably higher recovery rate of dislodged mites than sugar roll typically achieves, making it the preferred method for research and for any situation where accuracy matters more than sample survival, such as confirming whether a treatment worked.
Sugar roll, step by step
Shake the same size sample, roughly 300 bees, into a jar fitted with a mesh lid (hardware cloth or a specifically designed sugar-roll jar lid both work). Add two to three tablespoons of powdered icing sugar through the mesh, then roll and shake the jar gently for about a minute to coat the bees thoroughly; the sugar coating irritates mites' grip on the bee's exoskeleton and encourages grooming behaviour that dislodges them further.
Let the jar sit for a minute or two, then shake vigorously over a light-coloured surface or a container of water, so mites fall through the mesh along with the sugar. Count the mites recovered (rinsing with a little water helps them stand out against sugar residue), and calculate mites per 100 bees the same way as for alcohol wash. Return the bees to the hive afterward once they have been brushed free of excess sugar, since this method does not kill the sample.
The trade-off for keeping bees alive is a somewhat lower recovery rate: sugar roll tends to undercount actual mite load compared with alcohol wash, particularly in cooler weather when sugar clumps rather than coating bees evenly, or when bees are packed too tightly in the jar to be reached properly by the sugar.
Choosing between them in practice
For routine seasonal monitoring where you want to track trends over time without permanently sacrificing bees each time, sugar roll is the more practical everyday choice, especially in a small apiary where losing 300 bees repeatedly across a season is a meaningful cost. Because it is a comparative undercount, some beekeepers apply a mental adjustment, treating a sugar roll result somewhat more conservatively than the same number from an alcohol wash, or lowering their personal action threshold slightly to compensate.
Alcohol wash earns its place when precision matters most: confirming a treatment's efficacy by comparing before-and-after counts, verifying a borderline result before committing to treatment, or contributing data to any regional monitoring effort where consistency across many beekeepers and apiaries is valuable. Whichever method you choose, using the same one consistently across a season, at consistent 4-6 week intervals, matters more for spotting trends than which specific method you picked, since a consistent slight undercount is still useful for tracking whether mite levels are rising or falling.
Frequently Asked Questions
Which method gives a more accurate mite count?
Alcohol wash generally recovers a higher proportion of phoretic mites present in the sample and is considered the more accurate of the two standard methods, which is why it is preferred for research and for confirming treatment efficacy.
Do I need to kill bees to monitor Varroa accurately?
Not necessarily; sugar roll avoids killing the sampled bees at the cost of a somewhat lower recovery rate. For routine trend monitoring this trade-off is often acceptable, though for a precise, one-off decision an alcohol wash gives a more dependable number.
Why sample nurse bees near brood rather than foragers?
Nurse bees working near open brood tend to carry higher phoretic mite loads because mites preferentially seek out bees close to brood cells they can later invade, so sampling from a brood frame gives a more representative picture of the colony's mite pressure than sampling returning foragers at the entrance.
How often should I run one of these tests?
Most guidance suggests testing every four to six weeks through the active season, with additional checks after any treatment to confirm it worked and before making autumn treatment decisions, since mite levels can rise quickly later in the season as brood rearing slows.