Harvesting Mason Bees


Harvesting mason bee cocoons is a quick and easy way to ensure a healthier mason bee population!

But, if that wasn't enough, harvesting also allows you to:

  • Take Inventory of your mason bee population;
  • Share your extra mason bee cocoons (and knowledge) with local friends and neighbors; and

We know this can be a little intimidating for first-timers, so we've created a simple guide with video tutorials to help you along the way. You'll learn the importance of harvesting cocoons, the best harvesting practices for our three different types of nesting materials (natural reeds, wood trays, and cardboard tubes), and how to clean and store your mason bee cocoons for healthy spring bees!

Why it is Important to Harvest Mason Bee Cocoons 

Productive bee nests are a buffet of food resources for pests and parasites, and the proximity of managed bees to each other allows diseases to spread quickly. We've repeatedly heard from researchers and bee raisers alike that the most effective control method of Chalkbrood, pollen mites, and Houdini flies is to harvest your mason bee cocoons in the fall!

As bee raisers, it's our responsibility to provide these pollinators with healthy habitats to forage and nest. So, if you install an artificial bee house, then you'll need to take the time to harvest if you want to see healthy future generations of bees in your yard. Fortunately, it's a quick and easy process!

Steps to Harvest Mason Bee Cocoons 

WHEN: Typically, you'll want to harvest in October or November.

If you had a particularly long, hot summer, you'd want to harvest closer to October than November. Just be sure not to harvest too early as mason bees still need summer temperatures to develop into adult bees fully. You can learn more about how temperature affects bees in our Climate Change: It's Bad for Bees blog post or Mason Bee Life Cycle article.

WHAT YOU'LL NEED: Before you begin, you'll want to set up your harvesting workspace and gather your harvesting tools.

A quick note: harvesting can be a bit messy! We suggest laying down a layer of newspaper or an old sheet to make cleaning up easier and not wearing your favorite clothes.

So, what makes harvesting messy? Well, you'll find all sorts of things inside the nesting materials. As expected, you'll find healthy mason bee cocoons, mud, and mason bee frass (poop). However, you may also find Chalkbrood, pollen mites (or other parasites), pollen loaves from bee eggs that never hatched, and possibly even dead mason bee larvae. The combination makes harvesting a fascinating but messy process. 

Don't be discouraged if you find any of these "problems" inside your nesting materials. We assure you, parasites and diseases are quite common! Many parasites are native predators that evolved alongside mason bees. But that doesn't mean we have to allow them to feast on our overwintering bees!

Harvesting significantly reduces the incidences of pests, parasites, and diseases and allows managed bees to thrive year after year!

HARVESTING TOOLS: Fortunately, most of the tools we use for harvesting mason bee cocoons are everyday items you likely already have! 

  • Clean tubs or bowls and a colander or strainer for washing bee cocoons;
  • Clean Bee (or bleach) in case Chalkbrood is present;
  • A Cocoon Comb for removing cocoons (for wood trays and natural reeds) - If you don't have a cocoon comb, you can use a Phillips head screwdriver, but harvesting will take longer since you can only remove cocoons one chamber at a time;
  • A HumidiBee for storing clean cocoons;
  • Paper towels or clean rags to pat cocoons dry after washing;
  • A stiff wire brush or old toothbrush to remove stuck on debris (for wood trays); and
  • Scissors to open nesting materials (for Cardboard BeeTubes and Inserts).

Pro Tip: Some of your Natural Reeds or BeeTubes may have been partially filled with cocoons! Before opening, use a gauge stick to check if the materials are partially used or if they can be set aside for next year. Mark the stick at the length of the nesting tube and insert the stick into the open end of the nesting tube. If you can see the mark, there is a nesting chamber inside. If not, the reed or tube is empty, and you can set it aside for use next spring!

Step 1: Open Nesting Materials and Remove Cocoons

Wood Trays

1. Remove the green rubber bands and the cardboard backing (save both to reassemble the trays.

2. Lift the first tray, and using the Cocoon Comb, gently remove cocoons, mud walls, and other debris. Keep your removal tool at a 45-degree angle (see image below).

Shop Cocoon Comb


3. Remember to check both sides of the nesting trays for cocoons.

4. Brush away any pollen mites and mason bee frass with a stiff brush or old toothbrush.



5. If you find chalkbrood, spot clean with an old toothbrush dipped in a bleach and water solution (Ratio: 1 tsp. Bleach to 1 Cup Water). Or lightly apply CleanBee, a safe alternative to bleach, and use the old toothbrush to work the Clean Bee solution into the wood grooves.

6. Once clean and dry, reassemble the nesting trays by aligning the side grooves. Double-check the trays are snug and there are no gaps between the tracks.

7. Store over winter with cardboard backing and rubber bands attached to trays.

Natural Reeds

1. Pinch the mud-capped end between your fingers, and the reed will start to split. Don't worry; there won't be a cocoon at the open end of the reed. If you have a lot of reeds to open, you'll save your fingers by using a pair of pliers to pinch the mud-capped end!

2. Pry the reed apart and use a Cocoon Comb to remove the cocoons gently.

3. Once all the cocoons have been removed, you can throw the opened reeds into the yard waste or compost bin!

Cardboard BeeTubes with Inserts

First, remove the Easy-Tear Inserts from the Cardboard BeeTubes, then choose one of the options below.  

Option 1: Got lots of Inserts? Soak the Inserts in warm water for 10-15 minutes to loosen the glue. Do not soak for longer than 20 minutes!

Option 2: Tear or snip one end of the Insert, and it will easily unravel. Gently use your fingers to separate mason bee cocoons from the paper.

Cardboard BeeTubes

1. Tear or snip one end of the BeeTube and unravel along the spiral.

2. If a cocoon is stuck at the back end, gently push it out from the spin-closed end using an opened paperclip.

Pro Tip:If you find large, chubby, or plump larvae that fill the nesting chamber or non-mason bee cocoons, these may be wild bees or beneficial wasps. Read our Wild, Native Bees: Remove, Protect, & Store to learn what to do if you find these other beneficial pollinators!

Step 2: Wash Cocoons & Treat with CleanBee 

Mason bee cocoons are waterproof and can withstand about 30 minutes of soaking, but less time is always safer.

1. Fill a bowl or tub with cool water, add mason bees to the water, and gently stir to clean off mud and debris. Frass (bee poop) may require some friction to remove from the outside of the cocoon. If this occurs, gently rub cocoons between your fingers to remove stuck-on debris.

2. Once cleaned of debris, remove cocoons from the water. We've found a colander or slotted spoon makes for quick and easy removal of cocoons. Gently pat the cocoons dry with paper towels or a clean towel/rag. Allow cocoons to continue to air dry for about 30 minutes.

3. If you find evidence of Chalkbrood, spray CleanBee™ directly on mason bee cocoons. A light mist, evenly on all sides, is all you'll need! Alternatively, you could use a mild bleach solution (1 tsp. bleach to 1 cup of water). However, this method is more caustic, and you'll need to rinse cocoons with fresh water after soaking to remove excess bleach.

Pro Tip: Not all cocoons will be viable. Dead larvae that are C-shaped are a tell-tale sign of Chalkbrood infection and should be removed and thrown away. If you find cocoons with small holes, you may have a parasitic wasp infestation - remove and throw these out too! 

Step 3: Store Cleaned Cocoons until Spring 

Once clean, you should store mason bee cocoons in your refrigerator until the following spring. 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 34°-38° F (1°-3°C). Modern frost-free refrigerators have reduced moisture levels. After a few weeks in the fridge, your cocoons may begin to dry out. To prevent dehydration of mason bee cocoons, we've developed the HumidiBee Cocoon Humidifier.

Add about a tablespoon of water once a month to your HumidiBee container to keep cocoons from drying out.

Spores from cheese or foods past their prime are constantly circulating around your refrigerator, which can sometimes cause mason bee cocoons to become moldy. If you notice excessive mold growth (a little is OK) in your HumidiBee or on mason bee cocoons during winter storage, you can re-wash cocoons in cool water, pat dry, and spritz with Clean Bee™ to treat mold growth. Rinse the HumidiBee pads in warm, soapy water, let dry, then evenly spritz Clean Bee™ on both sides of the HumidiBee pads and mason bee cocoons.

Pro Tip: If mold is a persistent problem, place the HumidiBee container into a paper bag and close the top. Mold spores may have a harder time penetrating the paper bag.

Take Inventory and Share Mason Bee Cocoons 

We care about your mason bee-raising success and hope you harvest more mason bee cocoons than you need! 

Here are a couple of easy guidelines to help you know how many mason bee cocoons to keep during harvesting:

  • Keep about 1.5 mason bee cocoons per nesting tube. For example, if you have a 48-hole wood tray for mason bees, keep about 75 mason bee cocoons. Keeping a few extra will ensure that you have enough healthy adult bees emerge and nest next spring.
  • Keep a minimum of 10 mason bee cocoons per mature fruit tree.

Every yard is different, and with experience, you will get to know how many mason bee cocoons your garden, orchard, or farm can support. Many of our bee raisers like to keep about 200 mason bee cocoons to raise in their backyard.

Pro Tip: If you find the majority of your nesting materials are filled early in the season, you may want to increase your number of nesting materials or add an extra mason bee house to support the busy females. 

If you find yourself with extra mason bee cocoons, you can either share your extra mason bee cocoons (and knowledge) with local friends and family or participate in our Bee Buy Back Program.