What is Hygienic Behaviour?
Honey bees have many pests and diseases. Beekeepers put time and effort into learning about and controlling pests and diseases. It would be convenient if bees took care of their own colony health. This is not as far-fetched as it may seem.
Hygienic behaviour is a natural form of disease resistance. Hygienic worker bees uncap sealed cells containing diseased brood and remove the contents. In this way the disease is less likely to spread within the colony. Research has shown that hygienic behaviour helps control American foulbrood, chalkbrood, deformed wing virus and varroa.
Hygienic behaviour is not something that worker bees learn. It is a genetically-controlled trait. Workers either do it or not by instinct.
Hygienic behaviour is widespread but uncommon: most hives have only low levels of hygienic behaviour. By testing many colonies for hygienic behaviour, and rearing queens from the most hygienic mother colonies LASI has been able to build up the hygienic breeding stock used in LASI Queen Bees.
Benefits For Beekeepers
Research has shown that hygienic behaviour controls the following diseases:
Research at LASI has shown that hygienic behaviour significantly reduces varroa population increase. On average, over one year hygienic colonies had only 43% the varroa increase of non-hygienic colonies.
Deformed Wing Virus
Research at LASI has shown that hygienic colonies have greatly reduced levels of virus (on average, approximately 10,000 times less) and have greater survival. When a colony has workers with shrivelled wings, a symptom of a DWV, this is an indication that it will die soon. Requeening these colonies with hygienic queens greatly extended their lives.
American Foul Brood
Research in the USA has shown that hygienic behaviour is effective against AFB. Professor Marla Spivak of the University of Minnesota innoculated 18 hygienic and 18 non-hygienic colonies with AFB spores. Of the hygienic colonies, 7 had AFB symptoms but 5 recovered to give 2 with AFB. Of the non-hygienic colonies results, 18 had AFB symptoms but 1 recovered to give 17 with AFB.
Research in the USA has shown that hygienic behaviour is effective against chalkbrood. Professor Marla Spivak studied 18 hygienic and 18 non-hygienic colonies. Of the hygienic colonies, 6 had chalkbrood. Of the non-hygienic colonies, all 18 had chalk brood.
Does Hygienic Behaviour Harm Colonies?
Hygienic behaviour is not harmful. Research at LASI has shown that hygienic colonies do not remove healthy brood by mistake. Research in the USA by Professor Marla Spivak has shown that hygienic colonies make as much or more honey than non-hygienic colonies.
How Hygienic are Open-Mated Queens?
Research at LASI has shown that open mated daughter queens of highly hygienic breeder colonies are highly hygienic. The average level of freeze-killed brood removal was 95.5% over 2 days.
The Hygienic Bee Story at LASI
For the past 10 years, LASI (The Laboratory of Apiculture and Social Insects at the University of Sussex) has been doing research on honey bee hygienic behaviour. As part of this research we have been selecting, testing, breeding and rearing hygienic queens. We have received many requests over the years from beekeepers looking to obtain hygienic queens. We have established LASI Queen Bees to supply our hygienic bees to UK beekeepers.
How Do We Know If a Colony is Hygienic?
You cannot tell if a colony is hygienic just by looking at it. LASI tests colonies using the freeze-killed brood (FKB) removal bioassay developed by Professor Marla Spivak of the University of Minnesota. We take out a frame of brood from each colony to be tested and kill small patches of sealed brood using liquid nitrogen. The frame is then photographed and put back into the colony. Two days later we remove the frame, take another photo, and determine the proportion of cells cleaned out. When a colony removes 95% it is considered highly hygienic. LASI has some breeder colonies even more hygienic than that, removing 100% in one day. We normally test each colony 3 or 4 times for FKB-removal.