Assessing blue orchard bee (Osmia lignaria) propagation and pollination services in the presence of honey bees (Apis mellifera) in Utah tart cherries

Authors: Boyle, Natalie; Pitts Singer, Theresa

Submitted to: PeerJ
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2019
Publication Date: 9/5/2019
Citation: Boyle, N.K., Pitts Singer, T. 2019. Assessing blue orchard bee (Osmia lignaria) propagation and pollination services in the presence of honey bees (Apis mellifera) in Utah tart cherries. PeerJ. https://doi.org/10.7717/peerj.7639.
DOI: https://doi.org/10.7717/peerj.7639

Interpretive Summary: The blue orchard bee is a commercially available, native bee species recognized for its propensity to forage upon and pollinate tree fruit crops such as apple, almond and cherry. This study evaluated the impact and success of blue orchard bee and honey bee co-pollination of commercial tart cherry orchards in central Utah during 2017 and 2018. Three paired 3-acre sites were evaluated for cherry fruit set and yield 1) with and 2) without managed blue orchard bee releases. The use of blue orchard bees did not appear to increase cherry fruit set, fruit per limb cross-sectional area or fruit weight. The lack of detectable differences in yield likely resulted from a saturation of pollination services provided to local orchards. Sustainable in-orchard reproduction of blue orchard bees was achieved in 2017 but not 2018, possibly due to unknown changes to orchard management or environmental factors. While flying blue orchard bees in Utah tart cherries may support commercial bee propagation efforts, no subsequent influence on tart cherry yield was detected when paired with a high stocking density of honey bees.

Technical Abstract: Osmia lignaria is a commercially available, solitary bee species recognized for its propensity to forage upon and pollinate tree fruit crops such as apple, almond and cherry. This study evaluated the impact and success of O. lignaria and honey bee co-pollination of commercial tart cherry orchards in central Utah during 2017 and 2018 bloom. Three paired 1.2ha sites were selected for evaluation of cherry fruit set and yield 1) with and 2) without managed O. lignaria releases. O. lignaria supplementation did not measurably increase cherry fruit set, fruit per limb cross-sectional area or fruit weight. The lack of differences in yield is likely a consequence of local saturation of pollinator services supplied by managed honey bees throughout experimental orchards, such that no additive benefit of managed O. lignaria releases were attainable. Sustainable in-orchard propagation of managed O. lignaria populations was achieved in 2017 but not 2018, possibly due to unknown changes to orchard management or environmental factors. While flying Osmia lignaria in Utah tart cherries may support sustainable in-field bee propagation, their subsequent impacts on tart cherry yield were not detected when paired with a high stocking density of honey bees.