If you have a healthy production colony, it has from 10 to 15 thousands of bees at the beginign of year. If you have a healthly treated colony from last year, there will be from 100 to 200 varroa destructor mites. 
Number of bees at the beginning of year  
Number of Varroa Destructor on 1.1.  
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Treatment day in year success of treatment in % Kill forretic & brood varroa
Date of make divide
area of brood (dm2)  
is there a queen at the begining?
number of brood cells  
number of bees