Impact of pollen limitation and fungicide exposure on the lifespan of honey bees.

Honey bee colonies are frequently exposed to multiple environmental stressors, including pesticides and fluctuating pollen availability, yet their combined effects on worker longevity remain poorly understood. We conducted a full-factorial study to evaluate how fungicide exposure and pollen limitation affect the lifespan of adult honey bee workers (Apis mellifera) that developed under these stress conditions and in different sized colonies. Full-sized and nucleus colonies were placed adjacent to fungicide-treated or untreated oilseed rape fields. Half of the colonies were equipped with pollen traps to induce temporary pollen restriction over a four-week period, which covers a whole brood cycle. Emerging workers were monitored in both laboratory cage assays and under field conditions in mini hives. In the laboratory experiment, pollen limitation significantly increased mortality risk, whereas fungicide exposure and colony size influenced survival only through interactions with pollen limitation. In contrast, in the mini hive experiment, pollen limitation alone had no significant effect on survival, whereas fungicide effects depended on both pollen availability and colony size. The strongest reductions in longevity occurred under specific combinations of fungicide exposure, pollen limitation, and colony size, highlighting the importance of stressor interactions. Our findings demonstrate that worker longevity is shaped by the combined influence of nutritional, toxicological, and colony-level factors, rather than by single stressors alone. This indicates the importance of considering colony demography and nutritional conditions when assessing the potential consequences of plant protection products in agricultural landscapes.