Hi Brian: I am about 100 miles east of you. I had an identical  experience a 
few years ago with a backyard hive in Edmonton showing mite drops over 1000 
on each treatment with oxalic. My guess was that my hive, which was quite 
strong, was robbing out one or more weak hives in the neighbourhood which 
were infested with varroa. The new varroa arriving between treatments would 
enter the cells and reinfect a few weeks later. The varroa level finally 
dropped to a more normal level after six or seven  oxalic treatments but the 
hive died anyway.

My plan for this year is to treat with Apivar, removing the strips just 
about now and doing a final clean up with oxalic next week. The Apivar, 
being in the hive continuously, should get  the arriving mites before they 
can find a cell to hide in. So far it seems to be working, but that may just 
because they have not found any hives to rob.




Best Regards

Donald Aitken, Edmonton Alberta

53° 41' 51" N 113° 37' 32" W

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