How to Raise and Attract Mason Bees
The mason bee namesake comes from their habit of sealing their nests with mud. They typically nest in hollow reeds or holes in wood made by wood-boring insects. The blue orchard mason bee and the hornfaced mason bee are the most common here in Central Pennsylvania, although there are many. Mason bees are excellent pollinators in the early spring when many fruit trees are blooming. They are more efficient pollinators than honeybees and they only travel up to 300 feet from their nests, so if you grow mason bees close to your food forest, they will be there.
Mason bees are a solitary bee. They do not produce wax or honey. Every female is fertile and makes her own nest. The bees emerge from their cocoons in the early spring. Males emerge first. They wait for the females. When the females emerge, they mate. The males die, and the females begin work on their nests.
Females visit flowers to gather pollen and nectar. They create a mass of pollen and nectar. Once this is complete, the mason bee lays an egg on top of the pollen/ nectar mass. Then she creates a partition of mud, which also forms back of the next cell. This process continues until she’s filled the hole. Female eggs are laid in the back of the nest, and male eggs towards the front. Once a bee has finished with a nest, she plugs the entrance to the tube, and then may seek out another nest spot.
By summer, the larva has consumed all of its stores and then spins a cocoon around itself, entering the pupal stage. The adult matures in winter, hibernating inside its cocoon.
Benefits of Mason Bees
1. Excellent early spring pollinators
2. Will only sting if stepped on or squeezed.
3. Adds diversity of beneficial insects.
4. Inexpensive to attract or raise.
How to Encourage Mason Bees
You can purchase mason bee cocoons and bring them to your site, or you can simply encourage them to come by providing habitat. I think you must provide suitable habitat either way, because if you purchase mason bees, but do not provide suitable habitat, they will not survive. To provide good habitat, you need the following:
1. A good source of mud. My bees get mud from a clay pond forty feet from my nests.
2. Early spring sources of nectar. If you have fruit trees, stay away from chemicals, and have weeds such as dandelion, you should be fine. As an aside, I have a lot of Nanking Cherries. This tree is actually a miniature plum tree/ bush. It blooms first, so it is a good source of early season nectar.
3. Provide nesting sites. This may already be occurring, with wood boring insects creating sites for you or simply in hollow twigs. If not, you may want to drill 5/16” holes 4-8” deep in untreated wood blocks to provide nesting sites. The benefit of this is that it is easy and almost free if you have access to scrap wood. The negative is that, eventually they will stop using the block of wood as disease and pest pressures build, so you have to constantly put out new blocks each year or two.
How to Raise Mason Bees
1. Purchase your initial stock of cocoons.
2. Place the cocoons next to your nesting site when you are ready for them to emerge. I waited until the first blooms on my Nanking Cherries opened. I kept them in a baby food jar with holes in the top for air in my root cellar before that, so they would not emerge too early. Be careful, if you get a few days in the 50’s, they will start to emerge. Some people keep them in the fridge, when they get close to the spring, but make sure they have enough humidity. They should not be kept in the fridge for more than 2 or 3 weeks. People do that by putting them in the vegetable drawer or with a damp sponge.
3. Your nesting site should be 5/16” tubes 4-8” deep. Some people use wooden blocks, but cardboard tubes with parchment paper liner is better for harvesting cocoons and avoiding disease and pest pressures. If you use the wooden blocks, you will not harvest the cocoons. If you use cardboard tubes with parchment paper, in the winter you will harvest the cocoons and line the cardboard tubes with fresh parchment paper. This will keep your bees pest free.
4. Once your tubes are filled and sealed by your mason bees, it is important to prevent parasitic wasps from entering. This is usually late-May here in Central PA. You can prevent the wasps from parasitizing your cocoons by sealing your nests with bug screening.
5. Winter is a good time to harvest your cocoons, clean them, and place them in a cool dark place, until early spring. It is important not to expose your cocoons to too much time in a warm environment, otherwise they can hatch. No more than an hour, so take a few tubes in at a time. I placed my cocoons in a baby jar with holes cut in the lid for air then I put the jar in my cold cellar.
6. Go back to #2.
After doing the cardboard tubes with the parchment paper, I think it is too much trouble to harvest and clean cocoons. It’s not hard, but I feel like there has to be an easier way. I will still harvest my cocoons, and I think it is a good way to bring mason bees to your site, but I like the idea of providing the habitat for the bees to continue on their own. I’ve already got the mud with a pond, and plenty of early flowering plants. I will be on the lookout for blocks of natural wood that I can drill and place around my property. I know that these blocks of wood will only work for a couple of seasons, but if you have access to free natural wood, drilling out some blocks every other year is easier than harvesting, cleaning cocoons, and installing new parchment paper.