>Or-- you could go with zero tolerance.  This would involve putting down any colonies with mites. 

But you will still have mites and a huge detection effort, with expense that exceeds the cost of managing varroa the way most commercial beekeepers do.

The problem with this idea, as many jurisdictions with dreams of being varroa-free have found, is that detecting low levels of varroa is practically impossible.   Theoretically, and perhaps in practice, only one gravid varroa is required to infest an entire region.

As varroa levels increase, mites become easy to spot, but when there are only a few, they are undetectable.

Typically varroa has been in an area for a year or more before being detected.  After three years, they become obvious.

Once detected in an apiary, the assumption must be made that there are varroa in all hives, and by extension if a high degree of certainty is required, all hives within flying distance, even if no mites are seen there.

We have been over this when discussing Australia's' varroa vigil.  It is sufficient, we concluded, to prevent a collapse in Australia, but no absolute guarantee of freedom from mites for recipients of exported bees.

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