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  • Writer's pictureRaf Augustyn

UbeeO In Selection for Varroa Resistance

UbeeO is a groundbreaking new tool designed to rapidly and accurately measure a honey bee colony’s level of varroa resistance. Researched and developed over a decade by Dr Kaira Wagoner at Optera in North Carolina, USA, through her PhD and post-doctoral work, UbeeO just launched in the United States in spring 2024. Now Marlborough queen breeder Raf Augustyn, owner of Mana Queen, is hoping to incorporate it into his breeding programme, he explains the concept, as compared to other hygienic traits.

By Raf Augustyn

Mana Queen owner and dedicated breeder of hygienic bees, Raf Augustyn.

The honey bee colony is a superorganism, a group of synergistically interacting individuals that function as a unified being. They have evolved several social immune mechanism sets of behavioural and physiological traits that serve as self-preservation against entrance, establishment, and spread of pathogens in the colony. Hygienic behaviour – the detection, uncapping and removal of unhealthy brood from the colony – is one such example.

Selective breeding for hygienic behaviour has the potential to be a viable, long-term solution for varroa control because it places the implication of mite control on bees rather than beekeeper. It is not inclined to development of resistance by varroa and it does not harm bees or leave residues in honey. However, while the hygienic trait is elevated in many varroa resistant colonies, hygienic response does not always confer varroa resistance.

Several different testing methods have been developed by the queen breeders and researches over last two decades to quantify hygienic behaviour at colony level in order to make informed decisions in selection process. All of these methods have certain drawbacks including accuracy, difficulty of application, and in most cases it’s labour intensive and time consuming.

The Weimar needle stamp used to Pin Test brood. Photo: Mana Queen.

Pin Test (PT)

The pin test involves killing the developing pupae by making a pin-sized hole through the capped brood cells. Colonies are considered hygienic if, after 24 hours, bees successfully remove 95% or more of the dead pupae. However, bees not only detect dead brood through their olfactory (smell) senses, but they can also feel pierced capping’s through their antenna, thus limiting the accuracy of the pin test. This test can also be very tedious if one uses a single pin to punch through 50 capped cells on one frame of brood, as original protocols suggested.

Freeze Killed Brood (FKB)

To perform the FKB test, a frame containing sealed brood is removed from the colony and a standardized number of developing pupae are freeze-killed with liquid nitrogen. The frame is then returned to the colony. Twenty-four hours later, the number of freeze-killed pupae the bees successfully detected and removed is quantified. FKB can be a difficult test to perform as liquid nitrogen is not easy to work with. It can cause cold burns and asphyxiation. In addition, FKB does not always corelate well with chalkbrood resistance.

98% Hygienic behaviour – 49 of 50 pin tested cells successfully removed. Photo: Mana Queen.

Hygienic response to pin killed, or freeze brood does not always measure varroa resistance since tested brood is presumably not infected in the first instance, as we can’t see what is under the brood cappings. Incorporating this testing method into your breeding stock however, leads to better hive health and in turn colonies with greater overall resistance to pests and disease. In contrast, selecting for VSH can reliably achieve varroa resistance.

Varroa Sensitive Hygiene (VSH)

VSH is a genetic, heritable trait defined as the ability of honey bees to detect varroa in sealed brood and uncap the infested cell, disrupting their reproductive cycle. This leads to fewer varroa being able to reproduce in the colony. VSH bees do not disturb a cell that contains a non-reproducing mite. Where VSH is not present, less than 15% of varroa infested cells have non-reproducing mites, so when one finds non-reproducing mites in 40, 65 or 100% of the mite-infested cells, the colony has approximately 50, 75, or 100% of the VSH trait, respectively. The Harbo assay used to measure the number of non-reproductive mites per 100 cells is a skilled and laborious task if one wants to perform it on large testing population.

Unhealthy Brood Odour (UbeeO)

In 2019, researcher Dr Kaira Wagoner, of the University of North Carolina, described the discovery of specific cuticular hydrocarbons (CHCs) produced by brood infected with varroa mites. Dr Wagoner demonstrated that these unhealthy brood odours were increased in brood targeted for hygienic uncapping and confirmed that these compounds, synthesized in laboratory conditions, could be applied to brood cell caps to activate hygienic response. Wagoner then set out to develop rapid, precise and effective assay to predict varroa resistance at colony level.

VSH bees uncapping brood cells to interrupt varroa reproduction.

This new field test is performed by application of synthetic pheromones to a standardized number of capped brood cells, before returning the frame to the colony. Subsequent quantification of the bees’ hygienic response to treated cells is conducted after two hours. The UbeeO score is a percentage of cells uncapped. More cells uncapped, the higher the score. It has been shown that colonies capable of uncapping ≥ 60% of UbeeO treated cells in a two hour, early season test have significantly lower varroa infestation level at the end of the season and are significantly more likely to survive winter compared with lower scored colonies.

UbeeO method, does not kill brood, unlike PT, FKB or VSH, but places the unhealthy brood odour on the cappings of a smaller number of cells and can be performed more efficiently than any of the above described methods. There is also preliminary data suggesting that UbeeO assay may be useful in identifying honey bee colony resistance to diseases that are not associated with varroa such as Black Queen Cell Virus and Lake Sinai Virus.

The Mana Queen Philosophy

I believe that the bigger the testing population, the greater is the chance of finding individual colonies expressing the trait one is looking for. This is one of the reasons why I test a very large number of colonies. The other reason is of course genetic diversity. Maintaining high genetic diversity results in colonies exhibiting higher disease resistance. It also reduces the likelihood of inbreeding, it helps to adapt more effectively to different environmental changes and it enhances productivity. I have been selecting for hygienic behaviour since 2018. Sourcing from overseas a special needle stamp allowed me to test all my wintering hives fast and efficiently. I test approximately 1000 queens each year.

With base hygienic behaviour bred into my population, where bees have improved ability to deal with brood diseases, I have now started to test for VSH using Harbo assay.

While this is a very reliable test for varroa resistance, in its current form it is very labour intensive, resulting in me being able to perform it on about 100 hives at the most each season. These colonies are usually my best Pin Test scorers, and queens where I have noticed uncapping/recapping of brood on my spring evaluation round. I would love to be in a position where I am able to test for VSH in all my wintering colonies, like I do with a Pin Test, but currently it is unrealistic.

This is where UbeeO can make a difference. It is rapid, reliable test that accurately predicts varroa resistance abilities of tested colonies. It fits perfectly into my breeding concept of testing a large number of queens. Currently it is unavailable in New Zealand, but I am working with Dr. Wagoner to bring it in to the country for testing and research purposes. This September I plan to incorporate it into my spring evaluation round.

It's an expensive beast though, with the UbeeO formula costing about USD$25 per test. Therefore I encourage beekeepers to support Mana Queen by ordering our stock, for not just the benefit of your beekeeping, but to support something which has the ability to benefit the entire apiculture industry. 

References

Hygiene-Eliciting Brood Semiochemicals as a Tool for Assaying Honey Bee (Hymenoptera: Apidae) Colony Resistance to Varroa (Mesostigmata: Varroidae). Wagoner, J. G. Millar,  J. Keller, J. Bello, P. Waiker, C. Schal , M. Spivak, and Rueppell. 

Cuticular pheromones stimulate hygienic behavior in the honey bee (Apis mellifera). Kaira M. Wagoner, Jocelyn G. Millar, Coby Schal & Olav Rueppell.

Multiple benefits of breeding honey bees for hygienic behavior. Tal Erez, Elad Bond, Paz Kahanov, Olav Rueppell, Kaira Wagoner, Nor Chejanovsky, Victoria Soroker.

Time-accuracy trade-off and task partitioning of hygienic behavior among honey bee (Apis mellifera) workers. Katherine R. Barrs (1,2) & M. Omar Ani (1,3) & Kimberlyn K. Eversman (1,4) & Jonathan T. Rowell (5) & Kaira M. Wagoner (1) & Olav Rueppell (1,6).

Brood Affects Hygienic Behavior in the Honey Bee (Hymenoptera: Apidae). Kaira M. Wagoner, Marla Spivak and Olav Rueppell.


 

 

 

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