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. 
Year   
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