Powdered Sugar Method
Lexikon
The powdered sugar method is a bee-friendly procedure for assessing the varroa infestation of a colony without killing the bees that are sampled.
The powdered sugar method is a bee-friendly procedure for assessing the varroa infestation of a colony without killing the bees that are sampled. A portion of bees, depending on the instructions between about 300 and 500 animals or around 50 grams, is brushed directly from a brood comb into a shaking jar with a fine sieve and dusted with dry powdered sugar. Shaking makes the varroa mites sitting on the bees lose their grip, so that they fall through the sieve together with the powdered sugar and can then be counted. The dusted bees themselves usually survive the procedure well and are returned to the colony.
Dry weather is crucial for a reliable result, because even slight 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 carrying out 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 should not be sacrificed, for example for small assessments during the course of 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 comb, so that a single sample can over- or underestimate the actual total 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 drawn with enough bees and from several comb alleys to obtain a representative picture, instead of relying on a single, randomly accessible comb.