How to Sample for Varroa: Alcohol Wash, Sugar Roll and Sticky Board Compared

Three kinds of sampling turn up in beekeeping guidance: shaking a measured sample of bees in a liquid or a powder and counting what falls out, or leaving a board under the hive and counting what falls onto it on its own. This page compares what each one is doing and how good the count that comes out of it is. It doesn't say what a count means for your colony; the varroa calculator does that arithmetic against the Honey Bee Health Coalition's (HBHC) current thresholds.

Alcohol wash, soap wash and sugar roll: a sample of about 300 bees

All three of these methods start the same way: HBHC has you scoop about 300 bees, roughly half a cup, from open brood comb. Alcohol and soap washes kill the sample; the sugar roll doesn't. HBHC states the trade-off plainly: "The alcohol/soap wash method is a more reliable method than the powdered sugar shake." The UK's National Bee Unit describes the same substitution from the other direction, and says the two are closer than that line alone suggests: "This method can also be performed by substituting the alcohol with powdered sugar to perform the non-lethal 'sugar-roll' method, where bees are shaken for 3 minutes in the powdered sugar." Its conclusion: "The results are comparable, and both are fairly reliable methods for determining mite populations in the hive". So a beekeeper who doesn't want to kill 300 bees each time can use the sugar roll and expect a broadly similar count to a wash, with somewhat more noise.

Both washes and the sugar roll depend on the sample size. The COLOSS BEEBOOK, a peer-reviewed reference for standard varroa research methods, explains why 300 is the number rather than a smaller scoop: "Sampling such a large number of bees takes into account variations among frames to obtain an average infestation rate, and does not damage the colony if a non-destructive method is used to loosen the mites from the bees". A smaller sample swings further from the colony's real rate purely by chance, in either direction.

The wash liquid itself has more than one recipe. Research protocols describe washing 300 bees in warm soapy water or in ethanol rather than the household 70% alcohol HBHC recommends for a hobby wash; the BEEBOOK's own method adds the bees to a jar and covers them: "1. Warm/soapy water or ethanol is added to jars to cover the 300 honey bees." Across its ether, soapy-water and ethanol variants, the BEEBOOK doesn't rank one as best: "None of these three methods is distinctly superior to the other and they can all be considered as reliable given that mite separation is done in a standardised manner (water always at the same temperature, or containing a standardized amount of soap etc.) and that the efficiency of the method is determined as described below." The common thread across every wash variant, and the sugar roll, is that the technique has to be done the same way each time for a count to mean anything against a threshold or against last month's count.

Sticky board: no sample, just what falls

A sticky board doesn't touch a bee at all. It's a tray or an insert coated with something mites stick to, left under the hive's open mesh floor for a set number of days, so the mites that die naturally and fall off adult bees are caught rather than lost. The BEEBOOK describes the setup in general terms: "covering the board with sticky material (e.g. Vaseline, glue, absorbent paper impregnated with vegetable oil). Such 'sticky boards' can be purchased or homemade." The National Bee Unit's own instructions for the same idea: "Using an open mesh floor, coat your monitoring tray with vegetable oil or petroleum jelly, or apply a sticky board, so that any living mites that fall down cannot return to the colony, and the dead mites don't get blown away when the tray is pulled out." The count that comes off the board isn't a sample at all, so it can't be turned into mites per 100 bees the way a wash or roll count can; the sticky-board mode of the varroa calculator works it out as mites per day instead, against a ladder of published levels rather than one threshold.

Because a board only catches mites that die and fall on their own, timing and colony state change what it can tell you. The National Bee Unit's fact sheet is direct about the trade-off: this natural-drop method "relies on mite drop as a proxy for the true Varroa population level in the hive, so it is not a particularly accurate method for determining mite numbers." Its saving grace is speed: "it is a quick and easy way to get an indication if there are few or many mites in the hive." HBHC goes further and places boards in its table of less reliable sampling methods, recommending they not be relied on alone. A board is a trend tool, best read alongside an occasional wash or roll rather than in place of one.

Which one to use

None of these sources hands down a single best method for every situation. A wash or roll gives a number you can compare directly against HBHC's Table 1; a board is easier to set and forget but reads mite pressure only indirectly, over days rather than minutes, and needs a longer count to mean much. This page stops at methodology on purpose: for what a count from any of them means for your colony, use the varroa calculator, which works both a wash or roll sample and a sticky-board count against current guidance and never names a treatment product or dose — for that, HBHC's own guide has a dedicated section.