Neonicotinoids, systemic insecticides that are distributed into all plant tissues and protect against pests, have become a common part of crop production, but can unintentionally also affect non-target organisms, including pollinators. Such effects can be direct effects from insecticide exposure, but neonicotinoids can affect plant physiology, and effects could therefore also be indirectly mediated by changes in plant phenology, attractiveness and nutritional value. Under controlled greenhouse conditions, we tested if seed treatment with the neonicotinoid clothianidin affected oilseed rape’s production of flower resources for bees and the content of the secondary plant products glucosinolates that provide defense against herbivores. Additionally, we tested if seed treatment affected the attractiveness of oilseed rape to flower visiting bumblebees, using outdoor mesocosms. Flowers and leaves of clothianidin-treated plants had different profiles of glucosinolates compared with untreated plants. Bumblebees in mesocosms foraged slightly more on untreated plants. Neither flower timing, flower size nor the production of pollen and nectar differed between treatments, and therefore cannot explain any preference for untreated oilseed rape. We instead propose that this small but significant preference for untreated plants was related to the altered glucosinolate profile caused by clothianidin. Thereby, this study contributes to the understanding of the complex relationships between neonicotinoid-treated crops and pollinator foraging choices, by suggesting a potential mechanistic link by which insecticide treatment can affect insect behavior.

新烟碱类杀虫剂是一种内吸性杀虫剂，分布在所有植物组织中并防止害虫，已成为作物生产的常见部分，但也会无意中影响非目标生物，包括传粉媒介。这种影响可能是接触杀虫剂的直接影响，但新烟碱类杀虫剂可以影响植物生理学，因此影响也可能是通过植物物候、吸引力和营养价值的变化间接介导的。在受控温室条件下，我们测试了用新烟碱类噻虫胺处理种子是否会影响油菜为蜜蜂提供花卉资源的生产以及提供防御草食动物的次要植物产品芥子油苷的含量。此外，我们还使用室外中生态系统测试了种子处理是否会影响油菜对开花的大黄蜂的吸引力。与未处理的植物相比，噻虫胺处理的植物的花和叶具有不同的芥子油苷特征。中生态系统中的熊蜂在未经处理的植物上觅食的量略多。处理之间的开花时间、花朵大小以及花粉和花蜜的产生都没有差异，因此不能解释对未经处理的油菜的任何偏好。相反，我们认为对未经处理的植物的这种小但显着的偏好与噻虫胺引起的芥子油苷谱的改变有关。因此，本研究通过提出杀虫剂处理影响昆虫行为的潜在机制联系，有助于理解新烟碱处理的作物与传粉昆虫觅食选择之间的复杂关系。