Wildflower plantings promote blue orchard bee, Osmia lignaria (Hymenoptera: Megachilidae), reproduction in California almond orchards

Authors: Boyle, Natalie; Artz, Derek; LUNDIN, OLA - Swedish University Of Agricultural Sciences; WARD, KIMORA - University Of California, Davis; PICKLUM, DEVON - University Of Reno; WARDELL, G.I. - Consultant; Pitts Singer, Theresa

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 2/25/2020
Citation: Boyle, N.K., Artz, D.R., Lundin, O., Ward, K., Picklum, D., Wardell, G., Pitts Singer, T. 2020. Wildflower plantings promote blue orchard bee, Osmia lignaria (Hymenoptera: Megachilidae), reproduction in California almond orchards. Ecology and Evolution. 10(7):3189-3199. https://doi.org/10.1002/ece3.5952.
DOI: https://doi.org/10.1002/ece3.5952

Interpretive Summary: Growing concerns over the availability of honey bee colonies to meet pollination demands has elicited interest in the use of non-Apis managed and wild bees to mitigate current pressures on the commercial beekeeping industry. The blue orchard bee is a native bee that shows great promise for commercial rearing and as a co-pollinator with or alternative pollinator to honey bees in managed orchards. We present results of a two-year study evaluating the use of blue orchard bees in combination with honey bees in California almond orchards, where three one-acre wildflower plantings were installed and maintained along orchard edges to supplement native bee and honey bee forage. Plantings were seeded with native wildflower species that have flowering periods known to overlap with and extend beyond almond bloom. To examine the success of O. lignaria as managed pollinators in almond orchards, we measured bee visitation to flowers, bee reproduction, and progeny outcomes across six 40-acre orchard blocks during 2015 and 2016. In 2016, pollen provision composition was also evaluated to confirm blue orchard bee use of the wildflower plantings. Closer proximity to the wildflower plantings significantly enhanced reproduction, and pollen analysis indicates regular visitation to the wildflower plots as far as 800 meters from nesting sites. This study highlights the importance and benefit of providing alternative floral resources to managed solitary bees in commercial agricultural landscapes.

Technical Abstract: Growing concerns over the availability of honey bee (Apis mellifera L.) colonies to meet pollination demands has elicited interest in the use of non-Apis managed and wild bees to mitigate current pressures on the commercial beekeeping industry. The blue orchard bee, Osmia lignaria (Say), is a native bee that shows great promise for commercial propagation and as a co-pollinator with or alternative pollinator to honey bees in managed orchards. We present results of a two-year study evaluating the use of O. lignaria in combination with honey bees in California almond orchards, where three 0.48ha wildflower plantings were installed and maintained along orchard edges to supplement native bee and honey bee forage. Plantings were seeded with native wildflower species that have flowering periods known to overlap with and extend beyond almond bloom. To examine the success of O. lignaria as managed pollinators in almond orchards, we measured bee visitation to flowers, bee reproduction, and progeny outcomes across six 16.2ha orchard blocks during 2015 and 2016. In 2016, pollen provision composition was also evaluated to confirm O. lignaria use of the wildflower plantings. Closer proximity to the wildflower plantings significantly enhanced O. lignaria reproduction, and pollen analysis indicates regular visitation to the wildflower plots as far as 800m from nesting sites. This study highlights the importance and benefit of providing alternative floral resources to managed solitary bees in commercial agricultural landscapes.