Richard and anyone else with thoughts or help.My first thoughts were EFB, and hygienic queens removing diseased larvae.  We have seen very few dead larvae and they were all in one hive.  After we pulled the supers we treated with Tylan.  It had no affect.  We then treated with Terramycin, and still had no improvement.  We have done mite counts with counts around 1-2%.  Nosema tests were either low or no disease found.  I never considered diploid drones to start with.  It was only after treatments failed to turn the hives around that I started looking deeper.
After doing some reading and finding that the diploids are removed almost immediately after hatching a light came on.  The larvae in our hives were disappearing too young for EFB.  Another fact that had puzzled me all summer was the abundance and health of the drone brood on the drone frames.  The frames were often sandwiched between worker brood frames that had the shotgun patterns and the drone brood patches were essentially solid, and uniform in age.
I realize that the probability of having multiple diploid drone layers is in the realm of aliens, but I have run out of ideas.  We now have all of our production hives with spotty brood.
Another thing that helped me rule out disease was the nucs.  Last years queens from the same producer were once in a lifetime queens.  When we re-queened the end of May we put the old queens in nucs made from brood frames from the hive they were removed from.  The end of July we re-queened these nucs with purchased queens from the same producer.  These nucs had performed extremely well all summer.  Shortly after re-queening we started finding spotty brood in most of them.
Normally our yearly loss is less than 10% for the past 6 years.  This year we are going to loose hives and one of my biggest concerns is, will we be able to re-populate these hives.  Until I found out about diploid drones I was sure it was disease.
Any help would be greatly appreciated.

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