Counting Varroa Infestation
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The natural mite drop on the varroa board is the simplest way to estimate a colony's infestation.
The natural mite drop on the varroa board is the simplest way to estimate a colony's infestation. Insert the board, leave it for three to seven days, count the fallen mites, and divide by the number of days. In summer, a paper towel soaked in cooking oil protects the insert from ants, which would otherwise carry mites away.
The institutes explicitly disagree on the damage thresholds, and the values depend on month and region. In Bavaria, high summer works with a traffic-light scheme: below 5 mites a day, keep observing; between 5 and 10, take countermeasures; above 10, intervene immediately. Baden-Württemberg starts treatment already from 5 mites. In autumn, Baden-Württemberg names 2 to 3 mites a day, Bavaria holds to 5, and for the broodless winter treatment the threshold drops to about half a mite a day. What is decisive is always the treatment concept of the responsible bee institute.
Regularity is what matters. A single count says little; the trend over weeks says everything. The picture becomes more precise with the powdered sugar or wash method on a sample of about 50 grams of bees.