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

Natalie K Boyle,Theresa L Pitts-Singer

doi:10.7717/peerj.7639

Abstract

Osmia lignaria is a commercially available, native 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 implementation of O. lignaria co-pollination with honey bees in central Utah commercial tart cherry orchards during 2017 and 2018 bloom. Three paired 1.2 ha sites were selected for evaluation of cherry fruit set and yield with and without managed O. lignaria releases alongside the standard honey bee hive stocking rate of 2.5 hives/ha. Osmia 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 measurable. An increase in managed O. lignaria populations was achieved in 2017 but not 2018, possibly due to unknown changes to orchard management or environmental factors. While flying O.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 standard stocking densities of honey bees.

Highlights

Fruit and nut tree crops comprise an important and critical segment of US agricultural production, which relies heavily, and often exclusively, upon insect pollination to achieve profitable yields
Our data demonstrated that O. lignaria pollination in this scenario had only a very limited, and not reproducible, impact on tart cherry pollination services
Previous work in almonds has demonstrated a functional pollination synergy when O. lignaria pollination is used in tandem with the traditional stocking density of honey bee hives (5 hives/ha; Brittain et al, 2013; Pitts-Singer et al, 2018)

Summary

Introduction

Fruit and nut tree crops comprise an important and critical segment of US agricultural production, which relies heavily, and often exclusively, upon insect pollination to achieve profitable yields. Cherries are the eighth most valuable tree fruit crop, valued at nearly $950 million in 2017 (Perez & Minor, 2018). With a 36% increase in tart cherry yield projected for 2018 from the previous year (Perez & Minor, 2018), it is increasingly important to consider the role and scope of insect pollination in the industry. As weather patterns during early spring blooms become less predictable, heavy rains and late frosts are expected to have measurable impacts on fruit yield (Cannell & Smith, 1986; Houston et al, 2018), in part because such inclement conditions do not support efficient honey bee foraging behavior.

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