Despite concerns about the status of wild bees, there have been few studies with repeated sampling of these insects at the same locations using the same method. There is an urgent need for longitudinal studies to understand species- and population-level dynamics and the drivers of change, especially in pollinator-dependent crop systems. We sampled wild bees in highbush blueberry fields in three multi-year sampling periods between 2004 and 2018 to determine changes in the wild bee community active during bloom. We captured 35% (162 species) of the known Michigan bee fauna across the three sampling periods. Andrena, Lasioglossum and Ceratina were the dominant genera, though species composition varied significantly between sampling periods. Wild bee abundance (measured as captures in the pan traps) declined 61% and richness declined 33% between the first (2004–2006) and second (2013–2014) sampling periods. This was followed by limited recovery in species abundance and richness in the third sampling period (2017–2018). Some species showed dramatic abundance declines, particularly the blueberry specialist Andrena carolina. By contrast, other species showed stable or increasing prevalence, and population trajectories were not correlated with life history traits. Potential causes of the observed decline include increased use of insecticides and extreme spring weather in 2012. While farms varied in pest management intensity and overall insecticide program risk increased over time, there was no correlation between bee declines and insecticide use. Insecticide program risk increased between the second and third sampling periods, while most species increased in abundance. We therefore conclude the observed declines were most likely caused by extreme spring weather in 2012 resulting in widespread damage to flowering plants that provide resources for bees. Long-term monitoring to identifying species more vulnerable to environmental perturbations can help guide conservation recommendations as extreme weather events become more common.

尽管担心野蜂的状况，但很少有研究使用相同的方法在相同的位置对这些昆虫进行重复采样。迫切需要进行纵向研究，以了解物种和种群水平的动态以及变化的驱动力，尤其是在依赖传粉媒介的作物系统中。我们在2004年至2018年的三个多年采样期内对高灌木蓝莓田中的野生蜂进行了采样，以确定开花期间活跃的野生蜂群落的变化。在三个采样期间，我们捕获了35％（162种）的已知密歇根蜂动物区系。Andrena，Lasioglossum和Ceratina是主要的属，尽管在采样期之间物种组成差异很大。在第一个（2004-2006年）和第二个（2013-2014年）采样期间，野生蜂的丰度（衡量为捕获在陷阱中的数量）下降了61％，而丰富度下降了33％。其次是在第三个采样期（2017-2018）物种丰富度和丰富度的恢复有限。一些物种的丰度急剧下降，尤其是蓝莓专家Andrena carolina。相比之下，其他物种显示稳定或增加的流行率，种群轨迹与生活史特征无关。观察到的下降的潜在原因包括2012年使用杀虫剂的增加和极端的春季天气。尽管农场的虫害管理强度各不相同，总体杀虫剂计划的风险随时间增加，但蜜蜂数量下降与杀虫剂使用之间没有相关性。在第二个和第三个采样期之间，杀虫剂计划风险增加，而大多数物种的数量增加。因此，我们得出结论，观察到的下降最有可能是由于2012年春季的极端天气导致对提供蜜蜂资源的开花植物造成广泛破坏。