By Garrett Okrasinski
A friendly Mason bee.
This year many of my friends and I intentionally hosted mason bees in our yards. We provided a hive with deep holes and placed mason bee cocoons out in the early spring. Buzzing hard at work, they filled my yard with excitement.
However the season has come to an end for our friendly mason bees. If you have a mason bee hive you may notice fewer bees working your yard and their holes are plugged up.
Mason bees are great native pollinators for the Pacific Northwest. Also known as orchard bees, these friendly bugs are awesome for pollinating fruit trees and other native trees and flowers. Looking like a housefly, mason bees have a dark green metallic body and antennas. Unlike what many people associate with bees, mason bees do not sting and are very docile. I was able to walk up within a foot of their hive and watch them work. They simply flew by and went about their day collecting pollen or mud. They burrow in existing holes, laying eggs and constructing a mud wall between each egg. These eggs or larvae, will then hatch in the early summer, eat pollen the parent collected for them and spin a cocoon.
Empty nests on left and filled nests on right
In the spring I met Missy Anderson, a well-known local public speaker, educator and advocate for these bees. Referred to as “The Queen Bee”, Missy runs a business renting out kits of mason bees. She will provide you with mason bee cocoons and their hive during the early spring and then collect them in June to protect the new cocoons. She carefully tends to each cocoon by hand, removing them from their masonry and washing them. She will refrigerate them until the next spring when they will get redistributed to new homes. Her passion and dedication reestablishing mason bees is very impressive. Look for her next spring if you are interested in hosting mason bees in your garden!
If you had mason bees in your garden you may notice most of their hive holes are filled up. Behind the little mud end cap are rows of new larva that will spin cocoons and eventually turn into next year’s bees. However, if left outdoors these cocoons will face many obstacles. Mites may burrow into the hive destroying the cocoons. Birds may find them and peck at the holes to snack on the delicate cocoons. And fungus may take over. Currently another predator is hatching, the Monodontomerus parasitic wasp. The wasp will lay eggs in the mason bee cocoons and once the wasp eggs hatch they will then eat each larva. Yikes!
A wasp! Photo courtesy of Missy Anderson
If you hosted mason bees in your yard, I recommend harvesting the larva to protect them for next year. Bring your hives inside and store them in the garage (if it stays warm) to let the larva finish spinning their cocoons and to protect them from pests. In September or October you can then fully care for and store the mason bee cocoons.
More nest options.
If your hive has paper tubes or stackable wood blocks, it allow for easy harvest. If your hive does not allow for cocoons to be exposed (holes drilled into a solid block), you cannot harvest the potential bees. For those that have paper tubes carefully slice the sides of the paper to expose the cocoons. Wood blocks can be untied to expose the cocoons. You may notice small black bits which is the larva excrement that gets pushed out of the cocoon. It is not a pest. Carefully collect the cocoon and gently wash the larva with a very dilute solution of bleach water to kill any mites or fungus. Pat dry with a towel. To keep the larva over the winter in the refrigerator you can use an old yoghurt container with holes poked in the lid. Place the larva in there with a lightly damp paper towel. Label it so that no one cleans the refrigerator out and tosses your bees! Missy recommends occasionally checking on them throughout the seasons to see if any mold or fungus is occurring. If you see any mold growth, simply wash them again and replace them back in the refrigerator for next spring.
More nest options.
If your nest has paper tubes or stackable wood blocks, it allows for easy harvest. If your nest does not allow for cocoons to be exposed (holes drilled into a solid block), you cannot harvest the bees. For those that have paper tubes carefully slice the sides of the paper to expose the cocoons. Wood blocks can be untied to expose the cocoons. You may notice small black bits which is the larva excrement that gets pushed out of the cocoon. It is not a pest. Carefully collect the cocoon and gently wash the larva with a very dilute solution of bleach water to kill any mites or fungus. The ratio is 1 tablespoon of bleach to 1 gallon of water. The temperature of the water should be luke warm so you can manipulate your fingers but not warm up the bees inside the cocoons. Pat dry with a towel. To keep the cocoons over the winter in the refrigerator you can use an old yoghurt container with holes poked in the lid. Place the larva in there with a lightly damp paper towel. Label it so that no one cleans the refrigerator out and tosses your bees! Missy recommends occasionally checking on them throughout the seasons to see if any mold or fungus is occurring. If you see any mold growth, simply wash them again and replace them back in the refrigerator for next spring. If the paper towel gets too dry, add a few drops of water so there is moisture in the container again.
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