Edlinger's Varroa Indicator
Work out the varroa mites in your colony
The number of varroa mites in a colony is a decisive factor for its health and survival. The Edlinger varroa indicator projects the mites found on the inspection tray onto the colony as a whole, giving you a clearer picture of where you stand.
The indicator is named after its developer. It took five years to work out, during which many thousands of brood cells were opened and their mites counted.
Three details are all it takes: the day the mites on the tray were counted, how long ago the tray was last cleaned, and how many mites you found. From these the indicator works out the approximate number of mites in the colony, along with how many could be treated successfully with and without brood.
Result
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The assessment takes the month into account: in spring and late autumn the same mite drop weighs more heavily than in May and June. The projected mite figure itself is unaffected – it is the daily drop times 333 all year round.
Mite counts and treatments in one place
Counts and varroa treatments with date, product and quantity are entered at the apiary. Your treatment record builds itself along the way.
Record it all with the beekeeping appMore calculators for beekeeping
The calculation goes back to the beekeeper Kurt Edlinger, who developed it over several years. It is described, among other places, in the German Wikipedia article Varroamilbe.
Frequently Asked Questions
When do I have to treat against varroa?
The indicator shows three levels: up to about 900 assessed mites nothing is needed, above that keep watching, from around 1,100 treat without delay. Assessed means the projected figure, weighted by the month of the count.
Where do the thresholds and the factor 333 come from?
From Edlinger's own method, worked out over five years during which many thousands of brood cells were opened and counted. The calculator reproduces it unchanged: the daily mite drop times 333 gives the number of mites in the colony, weighted by a monthly factor between 0.9 in June and 1.8 in December.
This is a method in its own right and does not match the treatment thresholds of the bee institutes everywhere. Common guidance puts the limit at around one mite per day in May and June, and five to ten in July and August depending on the source. If you count in early summer, keep that in mind and follow the stricter figure when in doubt.
What does “treatable in a broodless colony” mean?
While there is brood, most mites sit in sealed cells and are protected from any treatment. In a broodless colony they sit on the bees and can be reached. The indicator works with fixed shares for this: around 80 per cent when broodless, around 20 per cent with brood. That is exactly what the winter treatment relies on.
What is the difference between the two treatment lines and “of those, on the bees”?
The first two lines come from Edlinger's method and state how many mites a treatment typically catches: around 80 per cent when broodless, around 20 per cent with brood. These are fixed shares, independent of the state of your colony.
The third line says something else: where the mites are sitting right now. In a broodless colony practically all of them are on the bees and can be reached; while there is brood, the larger share sits in sealed cells. This line follows your entry for the brood state and complements the projection without changing it.
Why does the month of the count matter?
The same mite drop means different things at different times of year. In spring and late autumn it weighs more heavily than in May and June, when the colony is at its strongest. The mite figure itself stays the same – only the assessment shifts.