Orchard Mason Bees

Honey bees are important pollinators, but they are not the only bees that pollinate our crops and fruit trees. Numerous species of bees are suitable pollinators. Some gardeners can benefit by enhancing the habitat for solitary bees.

The Orchard Mason Bee, Osmia lignaria, is popular among gardeners who want to improve fruit set on their trees. The Orchard Mason bees are not aggressive and not as much work as maintaining a honey bee hive. These solitary bees nest in holes in wood and use mud to create cells for their larvae rather than wax. The Orchard Mason Bee will gather a supply of pollen sufficient for larval development, then lay an egg and seal the egg and pollen with a thin layer of mud. This process is repeated to produce a series of chambers.

The adults live for about a month and will collect pollen during that time. To enhance pollination in orchards, Mason bee “traps” can be placed in areas where the Mason bees are common, then moved to orchards for Spring pollination. The traps consist of pine or fir 4 X 4’s with holes 3- 6 inches deep. The bees prefer holes that are 1/4 to 3/8 inch in diameter. The Mason bees will build nests in the holes all summer. The Orchard Mason bees will need a source of moist soil to build their nests. If the area is dry, a moist irrigated area can be created. The larvae will develop and overwinter in the nests.

Some orchardists will manipulate the bee life cycle by refrigerating the nests over the winter. The nests are warmed for a day prior to placement in an orchard that is just prior to flowering. To optimize pollination, 500-1000 females are needed per acre of orchard. Large populations of Orchard Mason bees have been developed in a couple of years. For homeowners with a couple of fruit trees, 3-5 bees per tree should provide adequate pollination.

For those who don’t have a shop, Orchard Mason bee houses can be purchased commercially.

Commercial Mason Bee House

About jjneal

Jonathan Neal is a retired Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
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