Scott > Others may want to jump in here. In my experience, drift is inevitable and inconsequential in a healthy yard.



Other studies indicate that varroa drift is consequential as unchecked populations increase - Seeley's being one that's particularly pertinent to the discussion about  Darwinian beekeeping. 


>"During the phoretic phase, Varroa mites are generally found between the abdominal segments of adult bees (workers and drones), so when bees drift between colonies, they spread both the phoretic mites and the viruses. Given that Varroa mites can be spread between honeybee colonies through drifting, we hypothesized that a population explosion of mites in one colony will easily spread among crowded colonies but not among dispersed ones. This hypothesis was tested experimentally over a 2-year period by establishing in a common environment two groups of 12 colonies, one with the hives crowded and one with them dispersed". 


>Crowding honeybee colonies in apiaries can increase their vulnerability to the deadly ectoparasite Varroa destructor

> Thomas D. Seeley and Michael L. Smith

> https://link.springer.com/article/10.1007/s13592-015-0361-2


BTW, Randy solicited  Bee-L earlier this year for participation in a Mite Drift Quantification citizen science project to gather data on this exact question.  

Bill Hesbach
Cheshire CT

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