Sulfoxaflor is a globally important novel insecticide that can have negative impacts on the reproductive output of bumblebee (Bombus terrestris) colonies. However, it remains unclear as to which life-history stage is critically affected by exposure. One hypothesis is that sulfoxaflor exposure early in the colony's life cycle can impair larval development, reducing the number of workers produced and ultimately lowering colony reproductive output. Here we assess the influence of sulfoxaflor exposure on bumblebee larval mortality and growth both when tested in insolation and when in combination with the common fungal parasite Nosema bombi, following a pre-registered design. We found no significant impact of sulfoxaflor (5 ppb) or N. bombi exposure (50 000 spores) on larval mortality when tested in isolation but found an additive, negative effect when larvae received both stressors in combination. Individually, sulfoxaflor and N. bombi exposure each impaired larval growth, although the impact of combined exposure fell significantly short of the predicted sum of the individual effects (i.e. they interacted antagonistically). Ultimately, our results suggest that colony-level consequences of sulfoxaflor exposure for bumblebees may be mediated through direct effects on larvae. As sulfoxaflor is licensed for use globally, our findings highlight the need to understand how novel insecticides impact non-target insects at various stages of their development.

中文翻译：

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氟啶虫胺和野蜂对大黄蜂（Bombus terrestris）幼虫生长的单独和联合影响

Sulfoxaflor 是一种全球重要的新型杀虫剂，可对大黄蜂 (Bombus terrestris) 群落的生殖产量产生负面影响。然而，目前尚不清楚哪个生活史阶段受到暴露的严重影响。一种假设是，在群体生命周期的早期接触氟啶虫胺会损害幼虫的发育，减少产生的工人数量并最终降低群体的繁殖产量。在这里，我们根据预先注册的设计，评估了在日光下测试以及与常见真菌寄生虫 Nosema bombi 结合使用时，氟啶虫胺酯暴露对大黄蜂幼虫死亡率和生长的影响。我们发现，当单独测试时，氟啶虫胺 (5 ppb) 或 N. bombi 暴露（50 000 个孢子）对幼虫死亡率没有显着影响，但发现了一种添加剂，当幼虫同时接受两种压力源时会产生负面影响。单独地，氟啶虫胺和 N. bombi 暴露均会损害幼虫的生长，尽管联合暴露的影响大大低于预测的个体效应总和（即它们相互作用的拮抗剂）。最终，我们的结果表明，大黄蜂磺胺嘧啶暴露的菌落水平后果可能是通过对幼虫的直接影响来介导的。由于氟啶虫胺在全球范围内获得使用许可，我们的研究结果强调需要了解新型杀虫剂如何影响处于不同发育阶段的非目标昆虫。尽管联合暴露的影响明显低于预测的个体效应总和（即它们相互对抗）。最终，我们的结果表明，大黄蜂磺胺嘧啶暴露的菌落水平后果可能是通过对幼虫的直接影响来介导的。由于氟啶虫胺在全球范围内获得使用许可，我们的研究结果强调需要了解新型杀虫剂如何影响处于不同发育阶段的非目标昆虫。尽管联合暴露的影响明显低于预测的个体效应总和（即它们相互对抗）。最终，我们的结果表明，大黄蜂磺胺嘧啶暴露的菌落水平后果可能是通过对幼虫的直接影响来介导的。由于氟啶虫胺在全球范围内获得使用许可，我们的研究结果强调需要了解新型杀虫剂如何影响处于不同发育阶段的非目标昆虫。