I've got a few nucs and hives that have spotty patterns. When you look into the comb you can see about +15% of the larva are off colored, amongst the health pearly white ones. Some of the brood dies (est. 15%) in the capped stage and rattles when the frame is tipped. I was thinking it was EFB and it would pass but that was a month ago. Is this Sacbrood or chalk brood (no mummies ever observed), or something else and how do I treat? The hives are plodding along and unless I can get this under control overwintering will spell their demise.
Any responses are appreciated.