Reconsidering the Selection Strategy in a Flemish Honey Bee Breeding Program: Towards Selection by Exclusion

Selective breeding is widely used to improve honey bee health and colony performance, commonly applying selection based on colony traits. Since 2017, a mass selection program in Flanders, Belgium, has ranked queens according to resilience, productivity and behavior traits. Using longitudinal data (2017–2024), we evaluated the effectiveness of this strategy by assessing colony performance across years and generations. Behavioral traits showed the clearest improvement over time, whereas progress in productivity and especially resilience-related traits remained limited. Offspring of top-ranking queens frequently failed to achieve overall ranking values comparable to those of their mothers; rather, they scored lower. For the traits Varroa index and spring development, offspring from lower-scoring queens often performed better, while offspring from higher-scoring queens tended to perform worse. These findings indicate that the current mass selection approach did not consistently result in cumulative genetic improvement. Factors such as open participation, limited breeding standardization, and insufficient paternal genetic control may have reduced selection efficiency. These results highlight the opportunities and challenges of implementing an accessible honey bee breeding program. Refinement of the current selection framework and evaluation of alternative strategies, such as selection by exclusion, may therefore be necessary to achieve more robust and resilient honey bee populations.