Bumblebees are important pollinators in agricultural landscapes that are facing global declines. Main pressures include food scarcity mainly due to the reduction of semi-natural habitats (SNH) and parasite-induced vulnerability. Even though intensive agricultural landscapes are poor habitats for bumblebees, the cultivation of mass-flowering crops (MFC) can provide a high amount of floral resources and therefore can promote pollinators. In contrary to SNH, which provide a high diversity of floral resources, MFC provide only monofloral, short-term and unbalanced resources for bees. We explored the direct and indirect effects of landscape composition (proportions of MFC, SNH, urban areas), landscape diversity, diversity of pollen diets and wax moth depredation on the growth and reproductive success of bumblebee colonies. We placed 44 experimental Bombus terrestris L. colonies in 22 agricultural landscapes. The study landscapes represented gradients of the cover of SNH, urban areas and oilseed rape (OSR) and differed in the availability of the mid-season flowering MFC faba bean (Vicia faba L.). We recorded colony growth and reproductive success of the bumblebee colonies, diversity of collected pollen types and depredation by the specialized wax moth Aphomia sociella L. We found no effects of landscape composition or landscape diversity on the diversity of pollen collected by the bees. However, we found a positive effect of landscape diversity on the reproductive success of bumblebees. Moreover, pollen diversity and the availability of faba bean interacted and resulted in higher numbers of young queens in landscapes without faba bean. In addition, colonies that collected a higher pollen diversity had a reduced A. sociella depredation. Increased parasitism had a cascading negative effect on the reproductive success of bumblebees by limiting colony growth. Our study showed that high landscape diversity and diverse pollen diets can enhance the reproductive success of bumblebees. A diverse diet even mitigated depredation by wax moths. To sustain vital bumblebee populations and their pollination services, diverse and floral rich habitat types should be conserved or restored in agricultural landscapes.

大黄蜂是面临全球衰退的农业景观中的重要传粉者。主要压力包括粮食短缺，主要是由于半自然栖息地 (SNH) 和寄生虫引起的脆弱性减少。尽管密集的农业景观是大黄蜂的不良栖息地，但大规模开花作物 (MFC) 的种植可以提供大量花卉资源，因此可以促进传粉媒介。与提供高度多样性花卉资源的 SNH 不同，MFC 只为蜜蜂提供单一、短期和不平衡的资源。我们探讨了景观组成（MFC、SNH、城市地区的比例）、景观多样性、花粉饮食的多样性和蜡蛾掠食对大黄蜂群生长和繁殖成功的直接和间接影响。我们放置了 44 个实验22 个农业景观中的Bombus terrestris L. 殖民地。研究景观代表了 SNH、城市地区和油菜 (OSR) 覆盖率的梯度，并且在中期开花的 MFC 蚕豆 ( Vicia faba L.)的可用性方面有所不同。我们记录了大黄蜂菌落的菌落生长和繁殖成功率、收集的花粉类型的多样性以及专门的蜡蛾Aphomia sociella 的掠食L. 我们发现景观组成或景观多样性对蜜蜂采集的花粉多样性没有影响。然而，我们发现景观多样性对大黄蜂的繁殖成功有积极影响。此外，花粉多样性和蚕豆的可用性相互作用，导致在没有蚕豆的景观中更多的年轻女王。此外，收集更高花粉多样性的菌落的A. sociella掠夺。通过限制蜂群生长，寄生性增加对大黄蜂的繁殖成功产生了连锁负面影响。我们的研究表明，高度的景观多样性和多样化的花粉饮食可以提高大黄蜂的繁殖成功率。多样化的饮食甚至减轻了蜡蛾的掠夺。为了维持重要的大黄蜂种群及其授粉服务，应在农业景观中保护或恢复多样化和花卉丰富的栖息地类型。