Both ecosystem function and agricultural productivity depend on services provided by bees; these services are at risk from bee declines which have been linked to land use change, pesticide exposure, and pathogens. Although these stressors often co-occur in agroecosystems, a majority of pollinator health studies have focused on these factors in isolation, therefore limiting our ability to make informed policy and management decisions. Here, we investigate the combined impact of altered landscape composition and fungicide exposure on the prevalence of chalkbrood disease, caused by fungi in the genus Ascosphaera Olive and Spiltoir 1955 (Ascosphaeraceae: Onygenales), in the introduced solitary bee, Osmia cornifrons (Radoszkowski 1887) (Megachilidae: Hymenoptera). We used both field studies and laboratory assays to evaluate the potential for interactions between altered landscape composition, fungicide exposure, and Ascosphaera on O. cornifrons mortality. Chalkbrood incidence in larval O. cornifrons decreased with high open natural habitat cover, whereas Ascosphaera prevalence in adults decreased with high urban habitat cover. Conversely, high fungicide concentration and high forest cover increased chalkbrood incidence in larval O. cornifrons and decreased Ascosphaera incidence in adults. Our laboratory assay revealed an additive effect of fungicides and fungal pathogen exposure on the mortality of a common solitary bee. Additionally, we utilized phylogenetic methods and identified four species of Ascosphaera with O. cornifrons, both confirming previous reports and shedding light on new associates. Our findings highlight the impact of fungicides on bee health and underscore the importance of studying interactions among factors associated with bee decline.

中文翻译：

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景观组成和杀菌剂暴露影响独居蜜蜂的宿主-病原体动态

生态系统功能和农业生产力都依赖于蜜蜂提供的服务；这些服务面临蜜蜂数量下降的风险，而蜜蜂数量下降与土地利用变化、农药暴露和病原体有关。尽管这些压力源通常在农业生态系统中同时出现，但大多数传粉媒介健康研究都孤立地关注这些因素，因此限制了我们做出明智的政策和管理决策的能力。在这里，我们调查了景观组成的改变和杀菌剂暴露对白垩病流行的综合影响，这种病是由 Ascosphaera Olive 和 Spiltoir 1955 属（Ascosphaeraceae: Onygenales）中的真菌引起的，在引入的独居蜜蜂 Osmiacornifrons (Radoszkowski 1887) 中（巨翅目：膜翅目）。我们使用实地研究和实验室测定来评估改变的景观组成、杀菌剂暴露和 Ascosphaera 对 O.cornifrons 死亡率之间的相互作用的潜力。幼虫 O.cornifrons 的白垩病发生率随着开放的自然栖息地覆盖率高而降低，而成虫的 Ascosphaera 流行率随着城市栖息地覆盖率的提高而降低。相反，高杀菌剂浓度和高森林覆盖率增加了幼虫 O.cornifrons 的白垩病发生率，并降低了成虫的 Ascosphaera 发生率。我们的实验室分析揭示了杀真菌剂和真菌病原体暴露对普通独居蜜蜂死亡率的累加效应。此外，我们利用系统发育方法并鉴定了四种 Ascosphaera 与 O.cornifrons，既证实了先前的报道，也揭示了新的关联。