I have recently fitted a Varroa screen into the bottom of my hive and
have discovered, as I expected that I have Varroa.
I counted 15 of the mites on the paper insert, within a twenty four hour
period.
 
How does one know what %  of infestation is in the hive?
When should I treat and for how long?  I plan on using Bayvarol strips.
As you can probably quess I am a novice who would appreciate any help.
I am situated in the NW of England.
Regards Alan