Queen Trapping

Queen trapping is a technique used to induce a brood break in a colony to control the Varroa mite population. Over a period of 36 days, the queen is trapped on a series of frames that are used as bait frames to attract and trap Varroa mites. The capped brood frames are then destroyed, reducing the mite load in the colony.

Varroa mites reproduce inside honey bee brood cells. Trapping the queen in a cage can prevent her from laying, which induces a brood break and reduces the mite population by slowing their reproductive rate. However, mites can survive on adult bees for many weeks until brood is present in the colony again and they can resume reproducing. If the queen is restricted to laying on a single frame at a time, the availability of brood is tightly controlled. These frames act as bait frames that attract the mites into the brood cells, where they are capped over and can then be removed from the colony, culling the Varroa mites. Using bait frames in this version of the method gives queen trapping the maximum effect in reducing mite numbers.

A brood break offers a good opportunity to eradicate the majority of mites in the colony if it is combined with an oxalic acid treatment¹. Oxalic acid-based medication is not suitable when there is brood in the colony, because it is lethal to open brood and cannot penetrate the wax cappings to kill mites in capped cells. However, oxalic acid-based medications have an efficacy of nearly 90% against mites living on adult bees² and, as there is nowhere else for them to go in a broodless colony, the combination can remove the vast majority of mites from the colony.

The bees’ ability to synthesise the glycoprotein vitellogenin is essential for brood food production and for winter survival, and it is impaired in adult workers that were parasitised by the varroa mite at the pupal stage³. When vitellogenin is not used up producing high-quality brood food, the high vitellogenin and low juvenile hormone levels make for a longer-living bee, i.e. the winter bee^3,4.

The procedure requires a certain degree of beekeeping skill, and the timing must be carefully judged to avoid leaving the colony short of foragers for the main nectar flow, or short of drones for mating.

Advantages and disadvantages

Queen trapping combined with oxalic acid treatment:

Advantages

• Up to 90% efficacy
• No chemicals required for the trapping itself
• Because there is less brood to care for, more bees are foraging, so a higher honey yield is possible
• The queen is less likely to be superseded when caged on a frame and still laying than when confined to a small cage and prevented from laying
• Longer-living winter bees
• A realistic method for the small-scale hobbyist

Disadvantages

• Time-consuming, requiring 5 visits to the colony
• Requires beekeeping skill and queen handling
• Requires a timetable and relies on exact timing of manipulations
• Potential weakening of the colony if applied too late in the season
• A less attractive method for the commercial bee farmer

Conclusion

Queen trapping combined with oxalic acid treatment is an effective method of varroa control for the hobbyist beekeeper. Because of the time it takes and the extra equipment required, it is unlikely to be an attractive option for the commercial bee farmer.

References

1. Anastasov, M. (2020). Queen Trapping and Queen Caging. BBKA News Special Series Issue, Integrated Pest Management, April 2020.
2. Büchler, R., Uzunov, A., Kovačić, M., Prešern, J., Pietropaoli, M., Hatjina, F. et al. (2020). Summer brood interruption as integrated management strategy for effective Varroa control in Europe. Journal of Apicultural Research, 59.
3. Amdam, G.V., Hartfelder, K., Norberg, K., Hagen, A. & Omholt, S.W. (2004). Altered physiology in worker honey bees (Hymenoptera: Apidae) infested with the mite Varroa destructor (Acari: Varroidae): a factor in colony loss during overwintering? Journal of Economic Entomology 97(3): 741–747.
4. van der Steen, J. & Vejsnæs, F. (2021). Varroa Control: A Brief Overview of Available Methods. Bee World 98(2): 50–56. DOI: 10.1080/0005772X.2021.1896196