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