3.3.5. Varroa infestation

Regular monitoring of varroa populations is not only a precondition for integrated varroa control, but also an important basis for the selection of mite resistant stock. Several different methods have been developed and tested with regard to systematic field evaluation of varroa densities (Lee et al., 2010). Please also refer to the BEEBOOK paper on varroa (Dietemann et al., 2013). We outline in Table 8 the methods commonly used to determine varroa populations in colonies and include information pertinent to the method’s uses in stock selection.

As a standard for performance testing, repeated checks of the mite infestation level are recommended. In periods of low infestation (usually early spring), monitoring natural mite mortality reveals best results. Sampling bees is more effective with higher infestation levels that occur later in the season (Büchler, unpublished data). The estimation of breeding values (see 4.1) for varroa resistance is based on mite population growth during the season. For these calculations, natural mite mortality during 3-4 weeks of the first main spring pollen producing bloom (e.g. willow, hazel, almond for phenological standardization of different climatic regions) is combined with the mite infestation of bee samples estimated during summer. Repeated measurements of the bee infestation in intervals of 3-4 weeks improves the accuracy of the test and allows prolongation of the test period without treatment against varroa until defined threshold values (usually 5-10 mites / 10 g bees, depending on environmental and beekeeping conditions) are reached.

Table 8. Methods for estimating varroa populations in honey bee colonies (see the BEEBOOK paper on varroa for more information on each method, including how to perform the method (Dietemann et al., 2012).





Natural mite mortality (i.e. mite fall or mite drop)



Results depend on the amount of emerging brood and colony size; sensitive to the presence of ants, wax moths et. al.

Bee samples – washing technique



Doesn´t work with very low infestation rates; independent from colony size; bees are killed

Bee samples -
powdered sugar



Similar to washing technique, but bees are kept alive; evaluation directly at the bee yard possible; depends on dry weather

Brood samples



Time consuming; can be combined with investigations on mite reproduction