Pollinator-dependent crops rely on the activity of managed and wild pollinators. While farm management and surrounding landscape can influence wild pollinator contributions, managed pollinator contributions may be primarily driven by their stocking densities, though this is not well studied across crops. We selected 20 southern highbush blueberry farms along two independent gradients of honey bee Apis mellifera L. (Hymenoptera: Apidae) stocking density (~1–11 hives/acre) and bumble bee Bombus impatiens Cresson (Hymenoptera: Apidae) stocking density (0 - 3 colonies/acre) ensuring that stocking densities were not correlated with farm or landscape attributes. Across farms, we observed managed and wild bee visitation rates, and measured yield estimates. Farms with greater bumble bee stocking densities had higher bumble bee visitation rates and yield estimates, but farms with higher honey bee stocking densities only received higher honey bee visitation rates at the end of bloom and did not have higher yield estimates. The main wild pollinator, the southeastern blueberry bee Habropoda laboriosa (Fabricius) (Hymenoptera: Apidae), showed higher visitation rates on organic farms and in late bloom. In general, higher visitation rates by honey bees, bumble bees, and H. laboriosa were correlated with higher yields. Our results suggest that yields are limited by bee visitation rates, and that within the stocking density ranges studied, increasing managed bumble bees, but not honey bees, increases their visitation rates. While H. laboriosa had the greatest effect on yield estimates, its activity appears to be limited by both a phenological mismatch with crop bloom and farm management.

中文翻译：

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蓝莓产量随蜜蜂访问率而增加，但蜂群放养密度并不能一致地预测蜜蜂访问率

依赖传粉媒介的作物依赖于受管理和野生传粉媒介的活动。虽然农场管理和周围景观会影响野生传粉媒介的贡献，但受管理的传粉媒介贡献可能主要受其放养密度驱动，尽管这在作物中没有得到很好的研究。我们沿着蜜蜂 Apis mellifera L.（膜翅目：蜜蜂科）放养密度（~1-11 蜂箱/英亩）和大黄蜂 Bombus impatiens Cresson（膜翅目：蜜蜂科）放养密度（0 - 3 个菌落/英亩）确保放养密度与农场或景观属性无关。在整个农场，我们观察了管理和野生蜜蜂的访问率，并测量了产量估计值。大黄蜂放养密度较高的农场的大黄蜂访问率和产量估计值较高，但蜜蜂放养密度较高的农场仅在开花结束时获得较高的蜜蜂访问率，并且没有更高的产量估计值。主要的野生传粉媒介，东南蓝莓蜜蜂 Habropoda labiosa (Fabricius) (Hymenoptera: Apidae)，在有机农场和开花后期显示出更高的访问率。一般来说，蜜蜂、大黄蜂和哈氏蜂的较高访问率与较高的产量相关。我们的研究结果表明，产量受到蜜蜂访问率的限制，并且在所研究的放养密度范围内，增加管理的大黄蜂而不是蜜蜂会增加它们的访问率。虽然 H. laboriosa 对产量估计的影响最大，