I have dealt with a problem hive for 2 months using OAV. Mite drops after every treatment are off the charts in my opinion. I am inclined to use harsher language in my journal.
Treatments started August 26 after honey supers were removed.
There have been 11 treatments and in every case this hive has dropped from 1000+ mites to a low of 236 on October 19. Progress! Yikes.
Treatment intervals have been 5 to 7 days. All other hives have zero to 4 mites on drop boards.
I surmise my Fall feeding has been turned into brood rearing, but after the end of September I am extremely reluctant to investigate at this latitude.
I did a, hopefully, final treatment today. I have not read of this situation before. I know the OAV is effective due to the massive mite drops after each treatment. 
Interesting to see the girls bringing in pollen today! What the heck could they be finding? Light yellow/ grayish, lots coming in?? The countryside is dry and brown.
We are going into the freezer this weekend, so I hope this foolishness comes to a rapid conclusion.
Best regards and scratching my noggin,
Brian
115W, 53N, El.850M

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