I have an overwintered nucleus colony that went queenless. The queen may have been poorly mated or maybe the result of a virus, I dont know but it happens. It's still too cold and early for queen rearing here and typically I would just write it off as a loss. The nuc is still fairly strong (not great) but probably on the edge of falling apart and becoming laying worker. I decided to give it a shot and try and save it anyway. I had TempQueen in the freezer, so I added one with a frame of brood, eggs, bees and should have a queen early next week. TempQueen is a plastic tube impregnated with a synthetic queen mandibular pheromone. The bees think they have a queen and behave normally until you can introduce a new queen. The workers immediately ran to the fake queen, hopefully I caught them early enough and it will hold them over. No guarantee it will work, Ill post how it goes. You can see the little tube of pheromone covered with bees in the photo.
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