What is a Harbo Assay?

This is a shortened explanation of the Harbo Assay. If you want detailed directions, you can find them on Dr. John Harbo’s site.
The Harbo Assay is a way to measure VHS (Varroa Sensitive Hygiene) in a colony. A frame of capped brood is tested by uncapping and inspecting pupa of the appropriate age. The queens are graded on a scale of 0 to 4, 4 being the highest score (80%-100% nonreproductive) and 0 would be the worst score (less than 20% nonreproductive). The Harbo Assay is measuring how much the bees are disrupting or limiting mite reproduction in the colony. One hundred cells with pupa of the appropriate age are uncapped and checked for mites, if no mites are found, another 100 cells should be uncapped, if there are still no mites then you are done and it is a score of 4.

When you find only mites that are nonreproductive in the first 100, you don’t need to do the second hundred. If you find reproductive mites in the first hundred, the second hundred should be done. We only graft from the highest scoring queens (4).