I once ran a study of mites in bees, sampled every month for 48 months, 16  
colonies per location, multiple locations, all in varying compass 
directions  around a smelter in East Helena, MT.  Results were that mites took out 
the  colonies faster, at the locations nearest the smelter.  
 
The point is, we had to open and sample bees every month.  We'd pop  the 
lid, pull the frame closest to the outside of the cluster, vacuum up bees  
from outside of cluster to look for tracheal and varroa mites.   Colonies 
farthest from smelter latest for a full two years, also had fewest  mites.  
Obviously our distant control were not harmed by the  intrusions.  We tried to 
avoid cold wind, but we opened these in below  freezing weather, many times.  
We did our best to not break the  cluster.  But we pulled lids, pulled 
frames, sucked up bees - all in winter  conditions, snow on ground, etc.  Hives 
were wrapped in black roofing felt,  and we always tried to work about 
mid-day.   Rule was to never open  them near end of day - we wanted to give bees 
some time to recover before  nightfall.
 
Jerry

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