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Splitting a Mason Bee Reed

Harvest Cocoons | Step by Step

  • Safeguard your bees’ health by harvesting cocoons. It’s the easiest and quickest way to reduce pests and disease. 
  • Simply take cocoons out of their nesting holes and store healthy cocoons. 
  • Harvesting cocoons only takes about 30 minutes each year.
  • Host a harvest party! Teach your children, neighbors, and friends about native bees!
  • Near Woodinville in Washington state? Come to our harvest party in early October. Watch Facebook and BeeMail for details.

According to a 2016 study by United Nations, 40% of insect pollinators worldwide are facing extinction and we should do what we can to protect bees. Harvesting cocoons helps to ensure your bees’ health by reducing pests and disease and it is a key component of the management of bee hotels. You can also spread awareness to your local friends and family by sharing cocoons! 

Pre-Harvesting: a mason bee filling her nestA glimpse inside a nesting tube

Mason Bee Cocoon Harvesting

Best done in October-November, although you can harvest until late winter. You can find a complete timeline for both mason and leafcutter bees in our Raise Bees section.

Tools Needed

  • A cool room to harvest in so the bees don’t warm up and think it’s already spring.
  • A smooth working surface that can get dirty from dry mason bee mud and debris.
  • Nesting material that you can open: BeeTubes, natural reeds, BeeTubes & easy-tear inserts, wood trays.
  • Philips-head screwdriver or popsicle stick and a stiff wire brush for harvesting from wood trays.
  • Wood skewer or long spaghetti noodle for gauging tubes or reeds for cocoons.
  • Scissors, a sharp knife, or a razor blade to assist in opening tubes or reeds.
  • Two large containers and cold water for washing cocoons.
  • Bleach solution and an old toothbrush for washing cocoons and spot-cleaning (only if chalkbrood is found).
  • Strainer or small container to scoop cocoons from water baths.
  • Magnifying glass to see all the interesting small things.
  • HumidiBee for winter storage of mason bee cocoons in the fridge.
  • BeeGuard fine mesh bag to store non-mason bee cocoons for the winter in a cold shed or garage.
  • Dustpan or vacuum for cleanup.

Getting Started

Inspect your tubes, reeds, or inserts for small holes on the outside as this could be evidence of a parasitic wasp. Set these tubes aside and harvest separately from the other tubes.

Be on the lookout for chalkbrood (pink, beige or black larva in the shape of the letter “C”). This is a highly contagious fungal disease that deserves special attention. Chalkbrood is spread by spores, so it’s important to contain the affected larvae to prevent spreading it.

For reeds, BeeTubes and inserts, you may need use a depth gauge on the tubes. You may have some nesting tubes that aren’t obviously used and this is our trick to tell if the tube has been used or not.

  • Crown Bees BeeTubes feature a small hole at the back end of the tube. Look through the open end of the tube and if you see light through the end it hasn’t been used. You can place this tube outside again next year. If you can’t see light through the end chances are a bee built a nesting chamber at the back. Place this tube in the harvest pile.
  • Natural reeds need to be gauged to see if they're occupied.
    • Make a depth gauge out of a long skewer or spaghetti noodle.
    • Insert the depth gauge into an unused tube or reed and mark the gauge where it meets the top of the empty tube.
    • If the mark on your gauge is outside of the tube, a mason bee has probably built at least one cocoon chamber in the tube. Move these to the harvesting pile.
    • If the marks line up between the gauge and the tube, it’s empty and you can use this again next year.
Unharvested reed above a harvested reed

Harvesting from Natural Reeds

  • Grasp the mud-capped end of the reed and squish it between your thumb and fingers. There aren't any cocoons at the mud capped end of the reed, just a thick layer of mud.
    • Alternatively, you can make a cut across the top of the mud cap and edge of the reed with a razor blade or pair of scissors and split the reed.
  • Pull the pieces of the split reed apart and gently remove the cocoons from inside.
  • To keep future bees healthy, we do not recommend reusing reeds.
Squeeze reed at mud cap  
Pull the reed apart  
Remove cocoons from reed

Unharvested BeeTube above a harvested BeeTube

Harvesting from BeeTubes (formerly EasyTear Tubes)

  • Make a nick or tear in the open end of the tube with scissors or razor blade.
  • Unravel the entire tube. Some cocoons may stick to the tube, that’s okay, just gently pull them off.
  • Time-saving tip: Place the unopened tubes in a bucket of slightly warm water for 10-15 minutes. The glue holding the paper is water soluble and the tube falls apart easily. The cocoons are waterproof and typically are still dry afterward.
Cut into the tube at the mud-capped end with scissors
unwrap the tube and remove cocoons

Unharvested BeeTube and insert above a harvested insert

Harvesting from BeeTubes & Easy-Tear Inserts

  • Remove the insert from the outer tube by pulling on the outside edge of the white insert. You may need to use a pair of pliers to pull the insert out.
  • Make a nick or tear in either end of the insert with your fingers, scissors or razor blade.
  • Unravel the entire insert. Some cocoons may stick to the paper, just gently pull them off.
Cut into the insert with scissors
unwrap the insert and remove cocoons

cocoons in wood traysInsert screwdriver at an angle to gently scrape under the cocoons from the wood trays

Harvesting from Reusable Wood Trays

    • Remove green elastic bands from around trays, setting cardboard backing to side. Separate trays one at a time, removing cocoons as you go.
    • Use a Phillips-head screwdriver or popsicle stick, held at an angle, to gently lift and separate the cocoons from the channels. The angle of the tool is important to avoid crushing the cocoons.
    • Remember to clean both sides of each tray!
    • Place the cocoons in a small container.
    • If you find chalkbrood make sure to mark that area on both the top and bottom of that layer, so you can spot clean it with a bleach solution (you can use the same mixture for this and washing the bee cocoons). Treating the entire tray is not necessary, as it removes the beneficial scent of the mason bees and can cause the tray to warp. Chalkbrood is spread by spores, so it’s important to remove all the spores for future use of the trays.
    • Clean blocks with a dry scrub brush and restack them; note the grooves on the outer edges that must line up for proper stacking. There is no need to wash the trays unless you’re doing some spot cleaning for chalkbrood.
    • Bind the trays using the elastic bands, being sure to include the cardboard backing. If your cardboard backing is damaged, just cut another piece to fit on the back. It is important to keep your trays bound together to prevent warping.
    • Store trays in a dry location, like a garage or shed, until they’re needed next spring.

Freshly harvested mason bee cocoons showing pollen mites, mud caps, bee feces, and pests

What You'll Find

This is what you'll see as you remove all the contents from your nesting material (a wonderfully big mess!).

    • Cocoons: Mason bee cocoons look like very fuzzy raisins. Sometimes they are so fuzzy they may look moldy, but don't worry, they're not! Those are just cocoon fibers. The smaller cocoons contain male bees and larger cocoons contain female bees.

      You may find other bees' cocoons, great! You have other wild bees living near your garden and they found your nesting tubes. Keep these stored with your mason bees cocoons in the HumidiBee and let them emerge naturally the following year. You can also store these in the BeeGuard Bag in a cool location.
    • White larva: Some bees and solitary wasps that nest in the summer typically overwinter as big, white larva. They may be in bullet-shaped cocoons with a mud plug or they could be separated by grass or other vegetation. You may find some leftover spider or other insect parts that weren't consumed by the beneficial solitary wasp.

      When you find your first larva in the tube, stop opening it up and set it aside for winter storage. You will want to keep them in your garage in a protected container. You will warm them up in late summer for release similar to leafcutter bees. If found in a wood tray, keep them on a paper towel in the storage container. They have consumed all they need and should overwinter just fine.
    • Mud: Each mason bee cocoon is separated by a mud wall and each tube is capped with a thick mud cap, so you will find a lot of dried mud.
    • Bee frass: As the larvae eat their pollen loaf, they are also producing waste. The larvae push their waste out of their cocoon as they build it. These tiny dark brown flecks are baby bee poo! 
    • Pollen Loaves: Sometimes an egg isn't laid in a chamber, the egg doesn't hatch, or the larva just didn't need to eat all of its food. The leftover pollen loaves are firm, white to yellow or orange cylinders. If you are brave, eat one of the pollen loaves. You will find the taste relatively sweet due to the nectar inside. (To work at Crown Bees, everyone had to eat at least one...)
    • Nothing but pollen or mud: Toward the end of a female mason bee’s life, she can get a type of dementia. Her instincts tell her to finish holes with mud, or to gather pollen, and sometimes she does just, and only, that. She forgets to lay her eggs and simply caps the tubes.
    • Other types of bees or wasps: There are over 130 other species of mason bees and many solitary wasps that will use available holes to nest in. Not all bees and wasps use mud. Spring wasps might use pebbles; summer bees might use tree resin, chewed up vegetation and soil, leaf bits, downy parts of plants, etc.
    • Pests: Harvesting cocoons is the best way to get rid of the following most common and dangerous pests and diseases:
      • Pollen Mites eat pollen. They hitchhike on the backs of insects to find pollen. Unfortunately, they also hitchhike into nesting holes and eat the mason bee's collected pollen. Pollen mites are found throughout North America; more in moist climates than arid. The pollen mite either eats the egg and then the pollen, or just the pollen and the larva starves. The orange mass is mite feces and the mites themselves are clear and require a magnifier to see them. Luckily, harvesting your cocoons is the best way to discourage pollen mites from spreading to the next generation of bees.
      • Chalkbrood is a nasty fungus that can devastate your entire colony. Treat this problem with the highest concern. Chalkbrood is a fungus that, if its spores are ingested by a mason bee larva, kills the larva and turns it into a mass of more spores. Emerging mason bees (that weren’t harvested) brush past this chalky larva-shaped mass of spores and get the spores on themselves. They can then spread the spores to your mason bee house, flowers, and other nesting holes. Other mason bees will bring the chalkbrood into new holes, allowing the cycle to continue. Two or three years of this cycle can devastate your entire mason bee colony.
        • Chalkbrood cadavers are chalky and the skin breaks apart easily. A healthy cocoon resembles a fuzzy, plump raisin. Chalkbrood resembles the letter "C" and can range in color from salmon/brown to gray/charcoal in color.
        • Harvest your mason bee cocoons to minimize exposure of chalkbrood to emerging bees.
        • Washing cocoons and spot cleaning reusable wood trays with a bleach and water mixture of 1Tbl bleach to 1 cup water kills chalkbrood fungal spores.
      • Holes in cocoons are a sign of the monodontomerus wasp, or "mono". It is a tiny, black, parasitic wasp that lays its eggs within the developing larva. Mono females typically deposit their eggs through the side of a thin-walled nesting material but have been known to get through ends of wood trays as well. After the bee larva spins its cocoon, the mono wasp larvae eat the bee larvae. Unfortunately, the mono larvae are now nicely encased in a mason bee cocoon, which is tough to discern apart from normal cocoons. The wasps' development time is very short they can chew out through their chamber to attack other uncontaminated larvae elsewhere in your nesting material. The best way to control mono is to inspect your cocoons for holes and to make sure to protect your mason bee nesting materials in a BeeGuard Bag from late spring until fall cocoon harvest.
      • If you found something else, you can find more detailed information about pests and corresponding control solutions here.

Sort the Cocoons from the Other “Stuff”

    • Do a quick sort of cocoons from the other items, like mud walls, pollen loaves, and pests. Toss anything that’s not a cocoon. Count your cocoons and start planning how many mason bees you’ll want for next year. If you have some extra cocoons and would like to receive new nesting materials in exchange for your bees, check out our BeeBuyBack program.

Bee Buy Back

  • Fill out the form, put your excess cocoons in a box, and mail them to us in exchange for new nesting material or cash!
  • If you wish to participate in the BeeBuyBack program, don’t wash the cocoons you send to us — we’ll do it at our facility. No need for the bees taking two baths.


Mason bee cocoons are waterproof and can take a soaking, so we recommend washing the cocoons in cold water and bleach to remove any unwanted dirt and pests that may be stuck to the cocoons.

    • Bleach wash solution (only if you found chalkbrood!):
      • Large batches: mix 1 gallon cold water with 1 cup bleach in a large bucket.
      • Small batches: mix 1 cup cold water with 1 Tbl bleach in a bowl.
    • Drop the cocoons into the bleach mixture and vigorously stir the cocoons for 1-3 minutes. This will wash off any remaining mud or feces. Some cocoons may sink to the bottom, which usually means the cocoon has been compromised. Inspect the cocoon and toss it if it has a hole.
    • Using a small container or sieve, move the soaked cocoons to a bowl of fresh, cold water to rinse them off. Swirl the cocoons around for about a minute.
    • Remove the cocoons from the rinse bath with the sieve and spread them out on towels to dry. If you can, dry the cocoons outside or in a cool place, so the mason bees don’t feel warm and think it’s already spring!
    • Before you store your cocoons for hibernation, make sure the cocoons feel dry to the touch. If you can, dry the cocoons outside or in a cool place, so the mason bees don’t feel warm and think it’s already spring!
    • If you found chalkbrood in your wood trays, go ahead and use this bleach solution to clean the affected areas of your trays. Simply paint the solution it on the affected areas, re-bind the trays and allow them to dry.

Storage Over Winter

    • Your cocoons contain fully-formed mason bees that need to hibernate until next spring. The key to a good winter’s slumber is cold temperatures to keep the bee from using too much of its stored fats too quickly.
    • A fridge kept at 34-40°F/1-4°C is a great place to store the cocoons and keep your bees hibernating until flowers start blooming, but:
      • Cocoons need moisture. Our HumidiBee holds the cocoons and keeps the moisture level at an ideal 60-75% for long-term, winter storage. Modern frost-free refrigerators are very dry inside, and most have a moisture level of 20-30%. This is why we developed the HumidiBee!
      • It is important to check the HumidiBee monthly to make sure the pad is still moist and see how your cocoons are looking. It may be necessary to add approximately 1-2 teaspoons of water, depending on the refrigerator, every month. If you’d like a reminder to do this, sign up for BeeMail and we’ll remind you.
      • If you keep your refrigerator cooler, your bees will consume their stored fats slower and will last further into spring. Consider keeping your bees very cool if you have late springs. Do not freeze the cocoons. (They survive outside in Michigan just fine, but let’s not test this out.)
      • You may notice your cocoons are growing moldy. Don’t worry, it doesn’t hurt the bees unless it is really bad. It is likely caused by naturally-occurring mold spores from the food in your fridge (esp. vegetables, fruit, or cheese) and is easily remedied. Simply wash your cocoons in a solution of 1 cup cold water and 1 Tbl of bleach. Also, wash the pads and HumidiBee container in the solution. Let your cocoons dry in a cool area and place them back in the fridge. Consider placing the entire HumidiBee in a paper lunch sack. The spores have more difficulty penetrating the paper. You may have to repeat this process a few times over the winter.
      • If you’re storing your cocoons in a refrigerator that is not used very often, make sure to open it occasionally if you’re storing fruits that emit ethylene gas (especially apples). Ethylene gas is a released by ripening fruit and, though harmless to people, can be harmful to the mason bee cocoons. Opening the door occasionally also lets some fresh air in. Your bees will thank you.

  • Don’t want to refrigerate your bees? You can leave your bees in an unheated garage or shed, much like they would be in nature, but the bees will be subjected to temperature variations and may emerge before there are any blossoms, resulting in very hungry bees.

Releasing Mason Bee Cocoons

  • Once the daytime temperatures in your area have reached 55°F/13°C and you have open blossoms, it is time to release your mason bee cocoons.
  • You can share your cocoons with local friends as tiny ambassadors to spread the word about these gentle bees.
  • Though tempting, don’t send them to faraway geographic regions. The bees aren’t suited for different climates. At Crown Bees, we keep our bees sorted by geographic region to ensure they are sent back to the appropriate area.

Leafcutter Bee Cocoon Harvesting

Leafcutter bees overwinter as eggs, so the cocoons are best harvested in late winter or early spring. If you find leafcutter cocoons mixed in with your mason bee nesting material in the fall, that’s great, simply store the cocoons in a BeeGuard Bag in a cool area (like an unheated shed or garage) until the following spring. You can find an easy to follow timeline here.

Your leafcutter nesting material can be stored, unopened, inside a BeeGuard Bag in a cool location from the time you notice a stop in leafcutter bee activity. This is usually late summer or early fall, when the temperatures are consistently below 70°F/21°C. Then, about 6 weeks before your summer garden will be blooming, you can harvest your leafcutter cocoons.

Follow the steps above for opening the nesting material. It’s the same process, but the cocoons will look different. Leafcutter cocoons are vibrantly colored with greens, yellows, reds, and pinks from the leaves and petals they used to construct the cocoons.

After you have removed the cocoons from the nesting materials, do not wash them as the leaves are not as waterproof as the mason bee cocoons. We don’t recommend storing leafcutter cocoons in the refrigerator because they are more susceptible to mold, it’s best to keep them in a cool, unheated basement, shed or garage for their hibernation.