Native Pollinators On Farms
The terminology “Mason Bee” is somewhat confusing as it includes rare species in the genuses Anthidiellum and Dianthidium, as well as 23 common Osmia species, but in common parlance it is used as a synonym for a single managed and commercially available species, the blue orchard bee (Osmia lignaria lignaria). As a matter of practicality and to simplify things in the agricultural context, Farms at Work uses the term “mason bees” to mean only the Osmia species, with specific attention paid to those that are commercially available for pollination on farms.
Mason bees belong to the family Megachilidae and most have metallic blue, black, or green colouration. All mason bees currently available commercially in Canada belong to the genus Osmia and include the native blue orchard bee (Osmia lignaria) and the non-native horn faced bee (Osmia corniforns). There are 23 native species that are common in eastern Canada, all of which are active in the early spring or summer. All Osmia species are solitary, meaning they do not live communally in large social units like honey bees: Female Osmia make their own nests, amass provisions, and lay eggs within that nest independently of one another. Although they are all solitary, many mason bee species are gregarious, meaning they tend to locate their nests near each other. Other mason bee species are not gregarious, making them more difficult to manage for agricultural purposes. Osmia naturally nest in hollow stems or cavities and under rocks, depending on the species, and use a variety of materials including mud, grass, chewed leaves, and fine gravel to line their nests. Gregarious species can be induced to nest in nesting boxes containing hundreds of man-made nesting straws. These nesting boxes are sometimes referred to as “condos”.
Blue Orchard Bees:
At present, only Osmia lignaria propinqua, commonly known as the Blue Orchard Bee is available commercially in Ontario. This poses a problem as Osmia lignaria has a western (propinqua)and eastern (lignaria) subspecies, which should be kept separate in order to retain genetic diversity. Work is being done in the United States to make the lignaria subspecies commercially available, but it is still not widely available. The blue orchard bee produces only a single generation per year and is only active as an adult for a few weeks in early spring. Blue orchard bees make their nests in hollow stems or in commercial prepared nesting straws that mimic hollow stems. The blue orchard bee builds cells within these hollow stems using mud (thus the name “mason bee”). Blue orchard bees are important pollinators of orchard crops and blueberry crops because the bloom time of these crops correspond with the time in which the blue orchard bees are actively visiting flowers. Blue orchard bees are not of value as pollinators in later blooming crops, despite the fact that they are often marketed that way to gardeners.
Horn-Faced Bees:
The horn-faced bee is a native of Japan that was introduced into the United States in the 1970s as a managed pollinator. Its populations have largely remained under management though feral populations do exist. There are no commercial producers of horn-faced bees in Canada but they can be ordered from the eastern United States. Horn-faced bees are active for 6-8 weeks from April to June and as such may be useful as pollinators on orchard crops, blueberries, and other early-blooming fruit crops like haskaps or honeyberries. Like blue orchard bees, horn-faced bees nest in hollow stems or man-made straws and are gregarious.
A list of US and Canadian suppliers of mason bees can be found here.