The Varoa Problem

The selection of mite resistance in honey bee populations has been deemed a more sustainable solution to its control than varroacidal treatments. Because natural selection has led to the survival of some European and African honey bee populations to V. destructor infestations, harnessing its principles has recently been highlighted as a more efficient way to provide honey bee lineages that survive infestations when compared with conventional selection on resistance traits against the parasite.

European honeybees (Apis mellifera) hold a major role in pollinating crops and wild plants. Abiotic and biotic factors are a major threat to their populations. A well-known biotic factor is the mite Varroa destructor. Varroa is an external parasite that causes high mortality rates in honeybee colonies, and ranks fifth in terms of socioeconomic and environmental costs (Nentwig et al., 2018). Varroa fits on adult and immature honeybees while also spreading viruses to the honeybee colonies, thus leading to their death within a short period of time.

Even though it is not fully understood how Varroa contributes to colony mortality, controlling the mite population through various treatments is what is currently used by beekeepers to prevent spreading (Jack & Ellis, 2021; Rosenkranz et al., 2010). A few notable examples of treating Varroa are:

• Oxalic Acid a natural compound found in plants which can be used without significant harm to honeybees. Treatments have shown reduction of varroa mite populations without significant harm to honeybees.
• Thymol is a compound extracted from thyme oil. Its acaricidal properties have been fund beneficial to the treatment against Varroa mites. Thymol is in the form of gel pads or strips and can be placed within the hive. It has also shown reduction of Varroa infestations.  Thymol and is commonly used in organic beekeeping.
• Formic Acid is a naturally occurring substance found in ants and some other insects. It has been used as a Varroa treatment in the form of a solution or gel pads. Although its effects in treating varroa are positive, it should be applied with caution as it may harm the honeybee population.

Resilience to these compounds have made it more difficult for beekeepers to tackle the varroa problem. Therefore, instead of relying on chemical treatments, which are not sustainable in the long run, there is growing interest in breeding honeybee populations that are naturally resistant to these mites. Some European and African honeybee populations have already developed resistance through natural selection, and researchers believe that harnessing this natural selection process can be a more effective approach than traditional methods to solve the varroa problem (Guichard et al., 2020; Le Conte et al., 2020). This genetic resistance approach in breeding honeybee colonies based on specific traits has become popular among researchers who believe that by selectively breeding colonies with specific traits, it may be possible to develop mite-resistant honeybee populations.

Selective breeding plays a crucial role in the genetic resistance approach. In this approach, beekeepers and researchers carefully choose honeybee queens and drones with specific genetic resistance traits to mate, with the ultimate goal of producing offspring that exhibit heightened resistance to Varroa mites and the pathogens they carry. This practice allows the harnessing of genetic diversity within honeybee populations to enhance resistance, while also considering other desirable characteristics like honey production, gentleness, and pollination efficiency. By employing careful breeding strategies, beekeepers and researchers can develop honeybee populations that possess a range of beneficial traits, ensuring the long-term health and success of the colonies.

The genetic resistance approach allows beekeepers to reduce or eliminate the need for chemical treatments to control Varroa mite infestations. This not only promotes more sustainable and environmentally friendly beekeeping practices but also helps to maintain honeybee health and minimize colony losses. Furthermore, breeding for genetic resistance can lead to the development of locally adapted honeybees that are better suited to specific environmental conditions, further enhancing their overall survival and productivity.

While the genetic resistance approach seems promising, certain challenges exists. Maintaining genetic diversity within honeybee populations while selecting for specific resistance traits. Genetic diversity is crucial for the long-term survival and adaptability of honeybees, and breeders must carefully manage breeding programs to balance resistance traits with overall genetic variability. Additionally, ongoing research is needed to better understand the complex interactions between honeybees, Varroa mites, and viral pathogens, as well as to identify additional genetic markers for resistance.

The genetic resistance approach represents a proactive and promising strategy to enhance honeybee health and combat the challenges posed by Varroa mites and viral infections. By selectively breeding honeybee colonies with natural genetic resistance traits, beekeepers and researchers can contribute to the development of resilient honeybee populations. As we strive to safeguard honeybee populations and preserve their vital ecological role, the genetic resistance approach offers hope for the future of sustainable beekeeping and the protection of these invaluable pollinators.Top of Form

References:

Jack, C. J., & Ellis, J. D. (2021). Integrated pest management control of Varroa destructor (Acari: Varroidae), the most damaging pest Apis mellifera L. (Hymenoptera: Apidae) colonies. Journal of Insect Science, 21(5), 6. https://doi.org/10.1093/jisesa/ieab058

Guichard, M., Dietemann, V., Neuditschko, M., & Dainat, B. (2020). Advances and perspectives in selecting resistance traits against the parasitic mite Varroa destructor in honey bees. Genetics Selection Evolution, 52, 71. https://doi.org/10.1186/s12711-020- 00591-1

Le Conte, Y., Meixner, M. D., Brandt, A., Carreck, N. L., Costa, C., Mondet, F., & Büchler, R. (2020). Geographical distribution and selection of European honey bees resistant to Varroa destructor. Insects, 11(12), 873. https://doi.org/10.3390/insects11120873

Nentwig, W., Bacher, S., Kumschick, S., Pyšek, P., & Vilà, M. (2018). More than “100 worst” alien species in Europe. Biological Invasions, 20(6), 1611–1621. https://doi.org/10.1007/s10530-017-1651-6

Rosenkranz, P. (1999). Honey bee (Apis mellifera L.) tolerance to Varroa jacobsoni (Oud.) in South America. Apidologie, 30(2–3), 159–172. https://doi.org/10.1051/apido:19990206