The Importance of Harvesting Mason Bee Cocoons

Mason Bee on a Dandelion

Why Harvest Bee Cocoons?

People often ask why harvesting mason bee cocoons is important.

Here's a helpful analogy? You wouldn't get a new puppy, buy him a comfy pillow, and then put him in a dog house infested with fleas. If you did that your puppy would suffer, loose vitality, scratch endlessly, and can become very ill or worse. Instead, you would do whatever is needed to protect your puppy.

Pollen Mites Inside a Nesting Tube

In the same way, mason bees have many natural enemy pests that claim countless numbers of bees each year.

The photo shows a cell filled with mites and mite poop. The orange is mostly droppings. The mites are numerous but they are somewhat clear colored. You will not find a bee larva in the cells with numerous mites. The mites destroyed the bee egg.

While the bees have few defenses against them, we can save them from the agony of defeat.

How Nature Works

Here's how it happens. In nature, wild mason bees find holes left behind by wood boring insects or look for hollow stems to use as nesting tubes. Pollen mites collect on the bee when foraging for pollen. While the female is building the cells inside the holes some mites drop off in the pollen pile.

The mites multiply rapidly numbering hundreds or thousands in a short time. The bee egg within those infested cells are killed. In the spring, the emerging bee must crawl through the wall of mites and immediately cling to the bee's body. The blossoms and tree leaves get infested with mites that are sctatched off by the suffering bees. Other bees pick up the mites. When the bees enter a new nesting hole, the mite invasion starts over again.

What You Gain From Harvesting Cocoons

  • Harvesting mason bee cocoons frees the bees from having to crawl through the mites in the spring. The  generation that emerges is stronger and healthier.
  • You are actually increasing bee populations and helping ensure the health of future generations.
  • You can keep track of the total number of cocoons. If you set out additional bee houses your bee numbers and cocoons will increase dramically each year.
Smaller Male Cocoon and Larger Female Cocoon

You will know the male to female ratio (male cocoons are a third smaller as shown in the photo). The ratio should be about 50/50. Too many males means your tubes are too short.

(Photo courtesy of Dave Hunter)

  • You can have an increase of fruit or flowers with the increase of pollinators.
  • North American native bees excel at pollinating North American trees and plants.
  • Refrigerating the cocoons keeps then in hibernation and allows you to put out the cocoons when you need them in the spring.
  • Refrigeration avoids the often ill-timed fatal releases that can occur in unseasonably warm spring weather before the trees are in bloom. Without pollen and nectar from blooms, the bees will quickly die.
  • It's fun and your children can learn about the life of bees.
  • Many commercial growers and resalers will purchase your healthy bee cocoons above what you need for your garden or orchard.
  • You become an environmentally aware, socially responsible person seeking to advance the cause of native bees. Since most people don't even know we have native bees, you will be the neighborhood native bee expert.

Other Methods of Protecting Your Bees

To prevent other pests from preying on the bee larva, gently remove the nesting boxes shortly after the bees stop flying. This is sometime around the first of May in most areas. Place the box in a net bag, i.e. BeeGardian Net Bag.You can use hose stockings of you prefer.

Place the net bag in a well-ventalated corner of the garage. This keeps the paracitic wasps, carpet beetles, and other insects from entering the nests.

In the fall you can harvest the cocoons and place them in a small humidity box (plactic container with vent holes and a damp paper towel). Make sure the wet towel is not touching the cocoons.

Do not havest the bees too early or they will be underdeveloped and die. November is a prime month for harvesting mason bee cocoons.

Cleaning Your Mason Bee Cocoons

Method One - Washing the Cocoons

This method involves washing the mason bee cocoons in a bleach and water solution. Don't worry, the cocoons are tough and will not be hurt. This does not kill the mites, but washes them off. The mites are extremely hard to kill, even with bleach.

  • Get a bowl of water and add a small amount of bleach to about a 5% solution.
  • Place the cocoons in the bleach water for about 3 to 5 minutes stirring them around.
  • Remove the cocoons and rinse them thoroughly with fresh water.
  • Lightly pad them dry with a paper towel. Do not store them in the refrigerator wet.
  • Do not use hot water or it may cause the larva to awake and think it is time to emerge. Use cold water and store in the refrigerator before they heat up to room temperature.

Method Two - Using sand to Clean Cocoons

This method was developed by Hutchings Bee Service, British Columbia.

  • Get a mesh screen with small holes large enough to allow sand to flow through, but not the cocoons. Farm stores often have a variety of screens sizes. You can make a simple sifting box if you like.
  • The most simple method is to form a cup with the mesh or lay the mesh flat over a bowl. Put the cocoons onto the mesh and carefully pour clean sand over the cocoons. The sand will brush off the mites as the sand passes over them. The mites are smaller than the grain of sand and pass into the bowl.
  • Pour sand over the cocoons several times to ensure pollen mites are gone. You can reuse the sand in the catch bowl to clean the mason bee cocoons. However, once the cocoons are cleaned throw the sand away in a place some distance away from any bee pollen source.

After Cleaning Cocoons

After cleaning the mason bee cocoons, put the clean cocoons in a breathable sealed container and place them in the crisper drawer of the refrigerator.  Place a damp paper towel in the container near the cocoons to provide humidity. Do not place the cocoons directly on top of the wet towel. Storing them in the refrigerator is the best method because you can keep them in hibernation until you are ready for them in the spring.

An important caution if storing cocoons in a non-heated garage during the winter:

A second option is to place the mason bee cocoons in a non-heated garage or shop building. If you experience several days of unseasonably warm weather, the heat may warm the cocoons enough to trigger an emergence. If that happens, but is followed by freezing weather, or if you have no blossoms yet, you will lose your bees. For this reason, it is better to keep them in a controlled environment.


Mason Bee Pollination vs Honeybee Pollination
Both mason bees and honeybees are incredibly beneficial to life on earth. Both bees pollinate, but their methods are different. Find out why researchers say the mason bees are the better pollinator.

The Orchard Mason Bee's Life Cycle and Behavior
Learn about our native Orchard Mason Bee life cycle. You will also see why this bee is so gentle and great for home gardens and backyard orchards.

Protecting Your Bees From Pollen Mites
Pollen mites can harm your bees. If you harvest your mason bee cocoons (and you should), learn how to remove mites from bee cocoons to ensure a good spring emergence.

Popular Types of Mason Bee Houses
The first step in managing native bees is selecting a bee house that fits your needs. Here's the latest scoop on the pros and cons of bee houses.

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Did You Know...?

Nature can only go so far in protecting bees. Harvesting your mason bee cocoons benefits your bees in more ways than you know. Don't skip this Step! Read this page to find out how.