Powdered Sugar Method
Lexikon
The powdered sugar method is a bee-friendly procedure for estimating a colony's Varroa infestation without killing the bees taken.
The powdered sugar method is a bee-friendly procedure for estimating a colony's Varroa infestation without killing the bees taken. A portion of around 50 grams of bees, that is, about 500 bees, is taken from a comb in the honey super or an edge comb without the queen and placed into a shaker jar with a fine mesh lid and dusted with dry powdered sugar. Shaking causes the Varroa mites sitting on the bees to lose their grip, fall through the mesh with the powdered sugar, and can then be counted. The dusted bees are returned to the colony; according to the Swiss Bee Health Service, however, the procedure shortens their lifespan.
Dry weather is decisive for a reliable result, because even a little moisture makes the powdered sugar clump, so that mites stick to the sugar instead of falling through, and the infestation is underestimated. For this reason most instructions advise taking the sample only in reliably dry weather and with completely dry, lump-free powdered sugar.
In everyday practice the method is popular above all where bees are not to be sacrificed, for example for small checks of the stock during the season. However, some specialist sources point out that Varroa mites are unevenly distributed within a colony and can accumulate in certain areas of the combs, so that a single sample can overestimate or underestimate the actual overall infestation.
A common mistake is to carry out the powdered sugar method in damp or cool weather and still treat the result as reliable. It is also sometimes overlooked that the sample should be taken with enough bees and from several spaces between the combs in order to obtain a representative picture, instead of being limited to a single comb that happens to be within reach.