Selecting colonies with low mite population (LMP) or reduced mite population growth (MPG) to breed from will result in decreased mite loads. Measurement is quick and simple to perform and will be part of every beekeepers’ toolkit: alcohol or soapy water washes. Selecting for low infestation will promote all traits that keep varroa populations low, even those that we do not know about (Figure 1).
MPG has been strongly linked with increased colony survival. LMP involves measuring the trait once, while MPG involves multiple measurements. MPG will provide more accurate results and more effective breeding. MPG is more reliable, as it ensures mite populations remain low over time rather than being a once-off test.
Figure 1. Varroa resistance traits selected for in breeding programs.
Varroa resistance traits selected for in breeding programs
| Hygienic behaviour (HYB): | unhealthy brood signals are detected by workers and they remove the brood, along with Varroa if that was the cause of illness. |
| Uncapping/recapping (REC): | workers detect signals from the brood that either they are unhealthy or infested with varroa, and remove the pupae and varroa. |
| Varroa sensitive hygiene (VSH): | workers detect that a pupae is infested and remove it, along with varroa. |
| Grooming and biting (mite biters; MB): | workers groom themselves or others to remove mites, which may cause damage or death of varroa. |
| Short development time (SDT): | bee brood have a shortened development time, meaning that varroa either doesn’t have enough time to produce viable offspring, or produces fewer viable offspring. The mite non-reproduction (MNR) suite of traits includes VSH, REC and HYB, and other traits that researchers have not yet identified how to select for. It includes any trait that prevents varroa from reproducing. Selecting for low infestation rates (LMP) or low mite population growth (MPG) will select for all the above traits, and any that we have not yet identified. |
Case study: Pol-line
The Pol-line was developed cooperatively with commercial beekeepers in the US in 2008. Getting buy-in from beekeepers is key to the development of stock that will be used by industry. The stock incorporated high performing genetics from commercial beekeepers with the VSH line developed at the US Department of Agriculture (USDA), which was selected for MNR and VSH at various stages. The program selects for survival, colony population, honey production, temperament, and LMP. Beekeepers can easily assess LMP using soapy water washes to determine the number of mites per honey bee.
The breeding stock is maintained by artificial insemination with mixed semen from all lines; — there are 9-31 lines available each year. The stock migrates between California, Mississippi, and South Dakota for honey production and almond pollination, ensuring it is well suited for commercial beekeeping realities.
Monitoring Varroa will be essential for all beekeepers.
More information
- Pol-Line VSH Honey Bees with USDA-ARS Drs Frank Rinkevich and Mike Simone – Beekeeping Today Podcast.
Acknowledgements
- Holmes, Gerdts, Grassl, Mikeheyev, Roberts, Remnant, Chapman (2024) Resilient beekeeping in the face of Varroa. AgriFutures Australia.
- https://honeybee.org.au/wp-content/uploads/2024/05/AGF575-Breeding-S3V2.pdf
- Plan Bee (National Honey Bee Genetic Improvement Program) is supported by funding from the Australian Government Department of Agriculture, Fisheries and Forestry as part of its Rural Research and Development for Profit program. The project is further supported by AgriFutures Australia, the Department of Regional NSW, University of Sydney, University of New England Animal Genetics and Breeding Unit, Better Bees WA Inc, Wheen Bee Foundation, Costa Group, Olam, Beechworth Honey, Monson’s Honey and Pollination, South Pacific Seeds, Australian Queen Bee Breeders Association, Australian Honey Bee Industry Council, and commercial beekeepers.
- Danka et al. (2016) Selection of VSH-derived ‘Pol-line’ honey bees and evoluation of their Varroa-resistance characteristics. Apidologie 47: 484-490
- Eynard et al. (2020) Descriptive analysis of the Varroa non-reproduction trait in honey bee colonies and association with other traits related to Varroa resistance. Insects 11: 492
- Guichard et al. (2020) Advances and perspectives in selecting reistance traits against the parasitic mite Varroa destructor in honey bees. Genetics Selection Evolution 52: 71
- Mondet et al. (2020) Evaluation of suppressed mite reproductive (SMR) reveals potential for varroa resistance in European honey bees (Apis mellifera L.). Insects 11: 595
- O’Shea-Wheller et al. (2022) A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission. Scientific Reports 12: 4852
- This article was peer-reviewed by Michael Holmes and John Roberts.
