Continuous hive monitoring reveals colony growth and activity differences among mite-resistant and Italian honey bee stocks

The choice of honey bee genetic stock represents an important management decision for beekeepers to improve resilience against biotic and abiotic stressors impacting their operations. Three different genetic stocks of honey bees (Pol-line, Russian and Italian) were monitored in southern Arizona field experiments for two successive 9-month periods (June to February). Continuous monitoring techniques and detailed hive assessments were used to measure differences in colony performance and behavior. On average, Italian colonies produced significantly more brood compared to both Pol-line and Russian bees and had significantly more foragers and adult bees on average than Pol-line colonies. However, both Pol-line and Russian colonies exhibited a faster rate of weight gain during the primary nectar and pollen flow season (June–September) and slower weight loss during the dearth season (October–February) compared to Italian colonies, which corresponded to results from published cage studies. Pol-line colonies started flight activity 10 min later on average than Italian colonies and ended daily flight activity about 30 min later on average than Russian colonies. There were no internal hive temperature differences among bee stocks, but Pol-line colonies maintained the highest carbon dioxide (CO₂) concentrations. Finally, Varroa mite levels in Pol-line and Russian colonies were significantly lower than Italian colonies and were correlated with brood area. Our findings highlight the potential advantages of Russian and Pol-line bees for use in commercial beekeeping operations. These observed stock differences could translate to improved crop pollination efficiency and reduced reliance on chemical mite controls.