Blue orchard bee (Hymenoptera: Megachilidea) origin and orchard growing region affect female retention at artificial nest sites in cherry orchards

Authors: SCALICI, MORGAN - Utah State University; McCabe, Lindsie; ALSTON, DIANE - Utah State University; PETERSON, STEPHEN - Foothill Bee Ranch; YOST, MATT - Utah State University; Pitts Singer, Theresa

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2023
Publication Date: 6/17/2023
Citation: Scalici, M.B., McCabe, L.M., Alston, D.G., Peterson, S.S., Yost, M.A., Pitts Singer, T. 2023. Blue orchard bee (Hymenoptera: Megachilidea) origin and orchard growing region affect female retention at artificial nest sites in cherry orchards. Environmental Entomology. 52(4):681-691. https://doi.org/10.1093/ee/nvad057.
DOI: https://doi.org/10.1093/ee/nvad057

Interpretive Summary: The blue orchard bee is a solitary, cavity-nesting bee used for pollination of spring-blooming orchard crops. Commercial stocks are obtained from various regions in the western United States and sold to producers and home gardeners across the country. However, it is not known if the blue orchard bee is regionally adapted such that where females choose to nest may be impacted by their population source. In spring 2019, blue orchard bees originally from California and Utah were introduced into three cherry orchards in both source locations (CA and UT) at times of the year when cherries bloom in those regions. Bee nest boxes were placed near (within 78 m) and far (500 m to 1 km) from a central location from which bees were released in each orchard. Cherry bloom was monitored, and bees were paint-marked, incubated, and released when floral resources were available. During the nesting period, observations of marked bees at each nest box were used to indicate whether females stayed close to the place from which they were released or if they dispersed to find nest boxes far away from release sites. Analysis of nesting bee counts in California orchards revealed a significant difference in female retention by population source; over twice as many UT bees were found at nest sites then were CA bees. Few females were found at nest sites far from release points. In Utah orchards, similar counts of CA and UT bees were found at near and far nesting sites. Thus, neither the likelihood of females staying close to release sites nor at distant sites were significantly affected by population source. An understanding of potentially consequential factors among orchard growing regions and bee management history is critical to employing regionally adapted bees as pollinators within and outside of their geographic origin.

Technical Abstract: The blue orchard bee, Osmia lignaria Say (Hymenoptera: Megachilidae), is a solitary, cavity-nesting bee used for pollination of spring-blooming orchard crops. Commercial stocks are sourced from various regions in the western United States and sold to producers and home gardeners across the country. However, it is not known if the blue orchard bees is are regionally adapted such that nest establishment may be impacted by their population source. In spring 2019, blue orchard bees sourced from California and Utah were introduced into three cherry orchards in both source and reciprocal states. Nest boxes were placed near (within 78 m) and far (500 m to 1 km) from the central bee release points. After the onset of Orchard orchard bloom was monitored, and bees were paint-marked bees were, incubated, and then released when floral resources were available. During the nesting period, observations of marked bees females at each nest box were made and used to evaluate female retention and dispersal pattern. Analysis of nesting bee counts in California orchards revealed a significant difference in female retention by population source; over twice as many UT bees established nests than did CA bees. Few females were found at nest sites far from release points. In Utah orchards, similar counts of CA and UT bees were found similar at near and far nesting sites. Thus, neither female retention nor dispersal were significantly affected by population source in UT. No directionality of dispersed females was observed. An understanding of potentially consequential variables among orchard growing regions and bee management history is critical to mitigate employingthe use of regionally adapted blue orchard bees as pollinators within and outside of their geographic origin.