The varroa mites feed on the body fluid of the adult bees and the pupa. They are only able to reproduce themselves in the capped brood cells. The mother mite starts to lay eggs about three days after the capping of the cell, every 30 h one egg. The first egg will produce a male and all following eggs will be females. The time for a mite to mature is about seven days.
Drone brood has a capped phase that is three days longer than the worker bees.
So more young mites are produced and it can be understood that for the mite it makes sense to prefer the drone brood. Without intervention from the beekeeper this will lead to the breakdown of the colony after one or two years. Important factors for the selection of a method are the effectiveness, danger of residues in wax and honey, optimum time of application, work and cost involved. A successful concept against varroa should not rely on just one treatment. This may fail in one year due to climatic problems, wrong application by the beekeeper or whatever and also promotes resitance to the treatments.