Alistair, I wouldn't be sitting on $7K of product you think is faulty. At the very least, you need to log this with both the company who supplied it and Elanco as well - they will probably take some of the strips to make sure they work. Make sure you keep any varroa from the riddled hives (dead in alcohol is just fine) because if you log in with Elanco then they will want some of the varroa for testing most likely.
We need a more user-friendly version of the Pettis (resistance) test available
Thanks John. Unfortunately a bit late now. Once I saw the carnage and losing more hives by the day, I panicked, drove down to the suppliers, got Apivar, and have put it in every hive that looks like it has a shot at making it to spring. And the rest, just to eliminate all possible mites.
As to the 7k of bayvarol, I know I am not alone in this, there are bigger and more influential beeks than me with the same issues, I'll wait for the outcome from whatever action they take & ride on their coat tails. Yeah lazy I know but I'm about done.
Next treatment round will start mid August, only a bit over 2 months away. All that can be done at this time has been done, I'm not opening any more hives now until then.
Just depending how things go I think losses will be limited to between 10% and 25%. This will not be a problem to make back up, I'm not worried about it. In fact I rather enjoyed the very intensive work I have done on the hives, and how I think I have pulled many of them back from the brink. More worried about the longer term implications of unreliable mite treatment.