Black Queen Cell Virus
This disease is caused by a virus
The virus attacks queen larvae
Signs in the colony
The infected queen cells develop dark brown to black cell walls. Within the cell the pro-pupae or pupae are pale yellow with a tough sac like skin (see Sacbrood). These pupae are full of virus particles.
This infection is closely associated with Nosema and with two other bee viruses (Filamentous virus and Bee virus Y). All three viruses only multiply in bees which have Nosema.
It has also bees seen in association with varroa infections.
As the disease is so intimately involved with Nosema control of the latter will help to prevent active infection. Likewise Varroa control will be essential.