Pollinating Fruit Trees with Blue Orchard Bees

Audio:  mp3

Apricots, plums, apples, cherries, and pears all need bees to pollinate their flowers. Traditionally, we’ve used the European honey bee, but now we know how to pollinate our fruit trees using a steely blue native bee, the blue orchard bee (Osmia lignaria). These wild bees fly nationwide.

In Utah, they live in foothill and lower montane habitats. Blue orchard bees are not social; every female is fertile and tends to her own tiny nest. Adults are the size of a chunky honeybee and are active for only 3-4 weeks in the spring. These bees naturally nest in the tunnels chewed by large wood-boring beetles in tree trunks. Each female partitions her tunnel into a series of tiny bee-sized rooms. Each room is stocked with a pea-sized provision of pollen moistened with nectar, followed by a single egg. Nest cells are partitioned, and ultimately capped, with mud, hence their other common name: “mason bees”.

You can have your own backyard population of blue orchard bees. An easy way to begin uses a short fat log that is seasoned and dry. Take a 5/16 bit and drill 20 or more holes radially 5 to 6 inches deep. Stand the log on end, facing the holes towards the southeast.

On cold mornings, nesting females bask in the sun before taking flight. If bees colonize your log, you will see the steely blue females busily coming and going all day long during fruit tree bloom. They tote their loads of dry yellow pollen in a brush of hair beneath the abdomen. Unloading that pollen at the nest requires some charming acrobatics that are well worth watching. While collecting pollen, female blue orchard bees pollinate your trees with hundreds of fruits resulting from each bee’s lifetime of work. Successive generations will nest for you every spring, but you’ll want to switch to replaceable nesting materials to prevent the accumulation of pathogens and parasites.

Details and links can be found at our Wild About Utah website.

This is Linda Kervin for Bridgerland Audubon Society.
Credits:

Photos: Courtesy & Copyright Jim Cane

Text: Jim Cane, Bridgerland Audubon Society
Additional Reading:

Resources:

https://www.sare.org/publications/bob.htm

https://www.ars.usda.gov/Research/docs.htm?docid=18333

https://www.pollinatorparadise.com/Binderboards/Hornfaced_Bees.htm