CORVALLIS, Ore. – Concerned about the decline of honeybees, one of the hardest-working food crop pollinators? Don't overlook the importance of a native pollinator of your fruit trees – the blue orchard mason bee.
"The diversity of flowers requires a diversity of pollinators," said George Hoffman, entomology researcher in Oregon State University's Department of Crop and Soil Science. "Also, if one disease affects one pollinator, it doesn't necessarily affect the others. Gardens need a diversity of pollinators so one disease or parasite won't wipe out all its pollinators."
Blue orchard mason bees are early-season pollinators native to Oregon, Washington and California, actively pollinating fruit trees in the wet and cold months of March and April. The mason bee, which has one generation a year, is slightly larger than a honeybee and shiny dark blue in color.
Research done by the U.S. Department of Agriculture's Agricultural Research Service Logan Bee Lab at Utah State University shows that blue orchard mason bees are superior to honeybees when it comes to pollinating apples, cherries and other native fruit trees in wet, cold conditions, Hoffman said. But if conditions are warm and favorable, mason bees and honeybees are equally effective.
Marking another difference between the two species, honeybees organize into colonies of worker bees led by a queen, whereas each mason bee female collects her own pollen and nectar and produces eggs.
"Each female is an independent operator," Hoffman said. "They don't have the luxury of waiting for better weather, or another year to reproduce."
Once mason bees emerge from their nests in March, they mate and consume pollen and nectar. For their nest, they find cavities in wood, such as beetle exit holes or artificial nests. Within the cavities they build five to eight cells separated by mud. They fill each cell with food on which they lay a single egg. The food source is a mixture of pollen and nectar formed into a little ball.
In late May and June, larvae develop inside the cells and metamorphose into pupae in the summer. They emerge from the pupal stage as adults in the fall and overwinter inside their cocoons.
Hoffman advises people to order live mason bees in cocoons online from commercial suppliers in October and November so they can arrive before Christmas. Start with 10-20 mason bee females, which means buying 30-60 cocoons. Mason bee females produce about two males for every female. It is the females who do the work of gathering nectar and pollen and pollinating flowers. Leave the cocoons in the original packaging and store them in the refrigerator until it's time to release them next spring.
One decision you need to make is what type of nest to provide, Hoffman said. The choices generally are Phragmite reeds, tubes with straw liners or wooden blocks with drilled holes. Drill holes into a solid or laminated wood, five-sixteenths of an inch in diameter, six inches deep and three-fourths of an inch apart. In the spring the nests need to be protected from wind and rain by a nest box.
When fruit trees start to bloom next spring, mount the nest box on a fence about 10-15 feet away from the fruit trees and watch brand-new adults emerge, Hoffman said.