Black Queen Cell Virus (BQCV)
BQCV is in the Dicistroviridae family of viruses and was first identified in 1977. It affects queen cells and the the pupa becomes yellow and the sac black (looking a bit like sacbrood but not connected). It is evident in the spring and summer, when queen cells might be expected in the hive.

The main method of transmission is via the oral route (horizontal), however it is possible that there is a vertical route as BQCV has been found in queen ovaries. There seems to be a connection with Nosema apis with BQCV appearing after nosemosis has appeared to clear up.

To diagnose BQCV infection the time of the year, nosemosis and the appearance should be identified.

It is not limited to Apis mellifera.
Scientific Beekeeping
Normal queen cell
Rob Synder
BQCV queen cell
Rob Synder