Harvest Cocoons | Step by Step
Harvesting cocoons is the best way to ensure bee health because it prevents the spread of disease and reduces pest populations. Harvesting cocoons is easy: just open the nesting holes, remove healthy bee cocoons, and leave pests and diseases behind.
Top three reasons to harvest hole-nesting bee cocoons:
- Sneaky, gnat-sized parasitic wasps that lay eggs inside of developing bee larvae.
- Chalkbrood, a deadly fungal infection that is picked up on flowers.
- Pollen mites, microscopic mites that eat the pollen loaf, starving and killing the bee larva.
Left unchecked, these parasites and disease can kill your bee house population. All of these threats to solitary bees naturally exist in your garden. Chalkbrood and pollen mites are spread when healthy bees must walk through an unopened and infected nesting chamber. To minimize these problems, harvest your bee cocoons and provide fresh and clean nesting holes each season.
- Crown Bees nesting materials are designed to be easy to open to harvest cocoons
- Harvesting cocoons can be a little messy but it is well worth your time and effort
- Harvesting bee cocoons is a great teaching activity for family and friends
How to Harvest Mason Bee Cocoons
Spring mason bees hibernate as fully formed adult bees inside of waterproof cocoons.
Harvesting mason bee cocoons is easy, quick, and allows you to:
Ensure the health of your mason bee cocoons
Take inventory of your mason bee population
Share extra mason bee cocoons with local friends and neighbors
Participate in Crown Bees nationwide BeeBuyBack program
- Open nesting materials and remove healthy cocoons
- Wash cocoons, adding Clean Bee if chalkbrood is found
- Store clean cocoons in your fridge in a HumidiBee container
When to Harvest Mason Bee Cocoons: Best done from October until December.
Get Ready to Harvest
Tools you Need: Scissors, a stiff wire brush or old toothbrush, paper towels, bowls and a colander or strainer for washing mason bee cocoons, bleach in case of chalkbrood, a HumidiBee for storing clean cocoons, and a Phillips head screwdriver or popsicle stick for removing cocoons.
Set up a Workspace: A a cool room to help keep the mason bee cocoons in hibernation (try opening a window) and newspaper or a pan for catching cocoons and debris.
Make a Gauge Stick: Check to see if your natural reeds or BeeTubes have been partially filled by making a gauge stick out of a thin stick or bamboo skewer. Mark the stick at the length of the nesting tube and place the gauge into the nesting hole. If the mark protrudes, there is a filled nesting chamber inside. If not, the nesting hole is empty and you can set it aside for use next spring.
Pro Tip: Easily check for mason bee mud at the small hole at the back end of our cardboard BeeTubes.
What You'll Find
What you'll see as you open your nesting materials.
- Healthy Bee Cocoons: Mason bee cocoons look like very fuzzy raisins, check to make sure there are no holes in the cocoons. When you find wild bees cocoons, store them in a BeeGuard Bag in an unheated garage or shed.
- White larvae: Some bees and solitary wasps overwinter as big (completely filling the nesting chamber), white larvae. When you can, close the nesting hole and store in a BeeGuard Bag in an unheated garage or shed over winter. Skinny white or pink larvae that are actively moving are most likely meal moth caterpillars and should be removed.
- Mud Walls: By now the mud walls and mud capped ends are very dry and crumbly.
- Bee frass: Those tiny dark brown flecks are baby bee poo! As the larvae eat their pollen loaf they are also producing waste that they push out of their cocoon.
- Pollen Loaves: Sometimes the egg doesn't hatch, or the larva just didn't need to eat all of its food. Pollen loaves are firm, white, yellow or orange cylinders.
- Just Pollen or Mud: A female mason bee can get a type of dementia and she fills the nesting hole with just mud or pollen.
- Pollen Mites: These tiny mites are picked up on flowers, the mites can eat all of the pollen and starve the bee larva.
- Chalkbrood: A deadly fungal infection that is picked up on flowers. Chalkbrood spores are ingested by a mason bee larva, kills the larva and it becomes a mass of more spores. Emerging mason bees walking through unopened and infected nesting chambers can spread the spores. Chalkbrood cadavers are chalky, the skin breaks apart easily, they resemble the letter "C", and can range in color from salmon, brown, gray or charcoal in color.
- Holes in Cocoons: A sign of the sneaky parasitic wasp called mono. Gnat-sized and black, mono lays its eggs within the developing larva. After the bee larva spins its cocoon, the mono wasp eggs hatch and eat the bee larvae. Inspect your cocoons for holes and protect your mason bee nesting materials in a BeeGuard Bag from late spring until fall cocoon harvest.
Harvesting from Natural Reeds
1) Pinch the mud-capped end between your fingers and the reed will start to split. Don’t worry, there is no cocoon at the open end of the reed.
2) Pry the reed apart along the split and use a Phillips head screwdriver or popsicle stick to gently remove cocoons.
Harvesting from BeeTubes
1) Tear or snip one end of the BeeTube and it will begin to unravel.
2) If a cocoon is stuck at the back end of the BeeTube, gently push it out from the pinhole side using an opened paperclip.
Harvesting from BeeTubes & Easy-Tear Inserts
1) Remove the insert by pulling on the outside edge of the white insert. You may need to use a pair of pliers to pull the insert out.
2) Tear or snip one end of the Insert and it will easily unravel. Use your fingers to gently separate mason bee cocoons from the Insert.Pro Tip: Got lots of Inserts? Soak the Inserts in a warm water solution to loosen the glue. Do not soak the Inserts longer than 30 minutes.
Harvesting from Reusable Wood Trays
1) Remove the big green rubber bands and the cardboard backing (save the cardboard to reassemble the trays).
2) Lift up the first tray and using a Phillips head screwdriver or popsicle stick, gently remove cocoons and mud walls. Keep your removal tool at a 45-degree angle.
3) Check both sides of the nesting trays for cocoons.
4) Brush away any pollen mites and mason bee frass. If you found chalkbrood, apply Clean Bee to affected areas.
5) Reassemble nesting trays by aligning the side notches, ensuring that the nesting holes are snug and there are no gaps.
6) Store over winter with cardboard backing and rubber bands attached to trays.
Sort the Cocoons from Debris
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 exchange them with us, check out our BeeBuyBack program.
- Fill out the form, put your extra cocoons in a box, and mail them to us in exchange for a Crown Bees gift card or check!
- 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.
How to Wash Mason Bee Cocoons
Mason bee cocoons are waterproof and we recommend washing the cocoons in cold water. We recommend using Clean Bee as a safer alternative to bleach.
- Make a bleach bath of 1 Tbl bleach to 1 cup water (1 cup bleach to 1-gallon water for large batches).
- Vigorously stir the cocoons for 1-3 minutes. Healthy cocoons float and cocoons with holes may sink to the bottom.
- Using a colander or sieve, rinse the cocoons with a bowl of fresh, cold water.
- Remove the cocoons from the rinse bath and spread them out on towels to dry. Spray cocoons with Clean Bee to treat chalkbrood.
- If you found chalkbrood in your wood trays, apply Clean Bee to the affected areas of your trays. Reassemble the trays and allow them to dry.
Winter Storage in a HumidiBee
- Mason bee cocoons are waterproof and should be stored over the winter in your fridge and washed as needed. The consistent cold temperatures of your fridge help the mason bees conserve their fat stores over the winter. We recommend setting your fridge temperature to between 34F-40F(1-4C).
- To prevent dehydration of mason bee cocoons, Crown Bees has developed the HumidiBee cocoon humidifier that retains moisture in today’s frost-free refrigerators. Place your clean and dry mason bee cocoons into the HumidiBee container and add a spoonful of water to the black HumidiBee pad.
- If you’re storing your cocoons in a refrigerator that is not used very often, make sure to open it occasionally to release ethylene gas (produced by fruit like apples).
- Add about a tablespoon of water once a month to your filled HumidiBee container and wash cocoons as needed.
- Mason bee cocoons can become moldy in the fridge and the source of mold is from cheese or other food. Treat mold by spraying cocoons and the HumidiBee container with Clean Bee. If mold is a persistent problem, place the HumidiBee container into a paper bag and close the top. Mold spores have a harder time penetrating the paper bag.
- Sign up for BeeMail for monthly reminders to add water to your HumidiBee container!
Leafcutter Bee Cocoon Harvesting
Leafcutter bees overwinter as delicate larvae and leafcutter bee 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, simply store the leafcutter bee cocoons in a BeeGuard Bag in an unheated shed or garage until the following spring.
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 70F(21C). You can harvest your leafcutter cocoons about 6 weeks before your summer garden will begin blooming.
Follow the steps above for opening the nesting material. It’s the same process, but the cocoons are vibrantly colored with greens, yellows, reds, and pinks from leaves and petals.
After you have removed the cocoons from the nesting materials, do not wash them as the leaves are not waterproof. 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 BeeGuard Bag in an unheated basement, shed or garage for their hibernation.