This document provides a brief overview of the diversity, natural history, conservation status, and management of North American mason bees. Mason bees are stingless, solitary bees. They are well known for being efficient pollinators, making them increasingly important components of our ecosystems in light of ongoing declines of honey bees and native pollinators. Although some species remain abundant and widespread, 27% of the 139 native species in North America are at risk, including 14 that have not been recorded for several decades. Threats to mason bees include habitat loss and degradation, diseases, pesticides, climate change, and their intrinsic vulnerability to declines caused by a low reproductive rate and, in many species, small range sizes.
Management and conservation recommendations center on protecting suitable nesting habitat where bees spend most of the year, as well as spring foraging habitat. Major recommendations are:
- Protect nesting habitat, including dead sticks and wood, and rocky and sandy areas.
- Ensure access to mud for nest construction.
- Avoid fires and mowing in potential nesting habitat, or alternate these management activities on an annual basis.
- Place wooden nest blocks in areas protected from the weather to promote breeding by cavity-nesting species.
- Ensure abundant and diverse spring-blooming plants, especially those in the heath, rose, and pea families.
- Avoid spraying pesticides on spring-blooming crops visited by mason bees, and avoid using systemic pesticides at anytime of the year.
- Avoid introducing managed mason bees to regions where they are not native to prevent the spread of pathogens.
- Where feasible, establish inventory and monitoring programs to better understand the distribution and population trends of native mason bees.
Conservation and Management of North American Mason Bees. 21 pp.
NatureServe, Arlington, Virginia.