Fall Mason Bee Cocoon Cleaning

Thank you to everyone who came out to learn how to clean cocoons!

Thanks to everyone who was able to join us in person at Bader Bee & Wine Supply last week to clean mason bee cocoons and bee houses. If you missed out, here is a summary of what was talked about. 

Good mason bee stewardship should involve cleaning bee cocoons in the fall. If you have a new bee house, we’ve found that by year 2 or 3 the disease issues tend to ramp up dramatically and the more you can do to prevent disease from spreading from generation to generation the better off your bees will be. Chalk brood, pollen mites, fly larva and other parasites can get in those tubes and it’s really hard for the bees to manage sometimes. So going through the process of cleaning out the healthy bee cocoons will keep your bee houses happy and healthy in the long term. 

The event also reminded me that some types of bee houses cannot be cleaned out, at least not in the fall. If you have a commercial house that uses bamboo or reeds that are glued into the structure or if it’s comprised of a solid piece of wood that has holes drilled into it, cleaning the cocoons and disease isn’t a reasonable task without destroying the house and the reeds that the bee cocoons are placed. To manage this, we recommend getting a second house and using an emergence chamber (we use 5-gallon buckets with lids and a small hole drilled in the side) that allows the bees that have nested in your bee house to hatch out in the spring and leave the emergence chamber to then, hopefully, populate your new bee house. Once all the bees have emerged, usually by late April or early May, you can clean the bee house using a dilute bleach water solution and pipe cleaners.

While that process is pretty easy, it is more work than some folks are willing to put into mason bees and that’s OK. You can just let your bees go and do their thing year after year. But know that disease issues will be ramping up every year in your bee house and you may want to consider getting rid of it for a new house after about 3 years anyway utilizing the same emergence chamber method described above. For new bee houses we always recommend using one that has removable tubes or comprised of wood trays that can be taken apart and cleaned relatively easily.

To clean cocoons you will need the following equipment:

You will need to extract the cocoons from the tubes either by cutting the outward facing end of the tube with scissors and unrolling the tube like a can of biscuit dough. If you have the wood trays you can also use a dull scraper to remove the cocoons. The cocoons will drop out and you will see that some are smaller (males) and larger (females). The cocoons are made of silk and usually have some small brown pellets known as frass. That is bee poop and it’s completely normal. You can then take the healthy cocoons and clean them in a bleach water solution made of 2 tablespoons bleach per 1 gallon of cold water. You’ll need a timer and will want to keep the bee cocoons in contact with the dilute bleach solution for no more than 2 minutes. Any longer may compromise the cocoons. You then want to rinse the cocoons with cold tap water to rinse off the bleach. Always use cool to cold water as the bees may awaken if you use warmer water and you don’t want that. 

The best way to accomplish all of this cleaning is to have a large bowl or basin of bleach water and a similar set up with plain water. You can then do the mason bee cleaning in a metal strainer that can be used to easily move the cocoons from one container to the other. Once you’ve rinsed the cocoons you can dry them off with a paper towel and set them in a dry place like a kitchen counter to let them air dry. Once they are completely air dried you can put them in a storage box to put in your crisper drawer in your fridge, or if you have a lot you can store them in a dry spot in your unheated garage or storage shed with a moist towel to keep the box contents humid. You can use an air-tight container like Tupperwear but you’ll need to open it regularly to allow for air exchange as the bees could suffocate if you left them in there all winter without fresh air. A box generally allows for enough air exchange and opening it monthly or so to check your refresh your moist towel will work just fine. The bee cocoons will live in your fridge or garage until about March 15 when we recommend you put them out into the houses you want them to populate. We will talk more about how to do that in the spring.

To clean out your house and trays we recommend using a bleach water solution made of 1 cup of bleach to 1 gallon of water. You can spray the house down and use whatever appropriate cleaning device (sponge, pipe cleaner, etc.) to get the nooks and crannies. You can scrub the trays and just wipe down the houses. Now is a good time to make repairs to the bee house if needed. 

And that's it.  It's pretty easy and if you have a bunch of houses or tubes to clean out, sitting down with friends or family on Thanksgiving to do some cocoon cleaning is a great way to spend the holiday.  If you want to see a great video of cocoon cleaning check out this one from Oregon State University Master Gardener program.