The horrors of mass-produced bee houses

Here are some reasons why cheap mason bee houses can end up hurting bee populations. I live in Pennsylvania (USA), so some of the issues might be specific to my location. And to the species that live here, of course. Check with your local authorities for more detailed advice.

1. Nesting blocks, tubes, reeds are not removable

Glued nesting materials is the number one reason why most commercial bee hotesl can become death traps. Because the nesting material cannot be removed and cleaned, over time there will be an increase in the population of parasitic wasps, parasitic bees, parasitic flies, kleptoparasitic mites, fungi, bacteria, and viruses. And you typically won’t see these dangers because the solitary bees will still use the hotel (they can’t help themselves). Here’s a photograph of the mites that tend to build up when bees reuse the same house every year. Sometimes they have so many they can’t fly anymore.

Hundreds of Krombein’s hairy-footed pollen mites on a mason bee. Image by @GeeBee60.

Ideally, empty out the house every year or two and give it a good cleaning. You can do this by removing all the filled nesting tubes at the end of the season (e.g., October) and storing them in an unheated garage or shed. Then, in the early spring put these nests inside a cardboard box that is equipped with a small exit hole — so bees can escape but can’t re-inhabit the nests. Finally, once everyone has emerged, clean the trays (brush, wash with bleach), re-drill holes (for blocks), and throw away reeds and paper tubes. While all this is happening, equip your (cleaned) house with fresh nesting trays, blocks, paper tubes, reeds, etc. All of this can’t happen, of course, if everything is glued in place.

If the above sounds like way too much maintenance, perhaps don’t buy a mason bee house. Get a garden gnome or a gazing ball.

2. Nesting tubes cannot be opened

Even if you clean the house every year and put in fresh tubes, the tubes filled in the prior year might be filled with parasitic flies and wasps. The ONLY way to get rid of them is to pry open the tubes and examine each pupa. And you can only do this if you use paper straws (that you can unwap) or if you use routered nesting blocks (that can be taken apart). So if you want the best accommodations for your solitary bees, opt for either of these designs. Bamboo is really difficult to split open, by the way, which is why I don’t use it for my bee hotels. Big Bamboo is probably going to sue me.

3. Nesting tubes open at back

If holes aren’t capped in some way at the back, parasites can easily gain entrance. Mason bees will plug the back with mud but it’s best to have a wall.

4. Reeds or holes with large splinters

Sharp edges inside the holes can snag and tear delicate wings.

5. Stems blocked at front

In houses that use bamboo, sometimes many of the sections are blocked off near the front by an impenetrable node. E.g., many of the tunnels are too short to be of much use.

6. Tunnels are not the right diameter

If reeds or bamboo are used in the house, make sure that they are all the diameter that supports the species of bee you want to attract. Solitary bees will end up using tunnels that are too wide but they will waste mud (and time and energy) filling them up. Bamboo houses are often a problem in this regard. (If you want to attract all different types of hole-nesting insects, then diversity in diameters is fine.)

7. Roof lacks overhang

Mass-produced mason bee houses are designed to be as compact as possible so they can be packed and shipped efficiently from factories in Asia. This usually means that they won’t have roofs that protect the nest entrances from water. Moisture causes larvae to rot and also seems to cause kleptoparasitic pollen mites to flourish. If your house is fine except for the roof, get creative and attach one. Or stick it someplace that is under a pre-existing structure.

8. House attaches to tree with string or hook

Mason bees start their lives as eggs on top of a mound of pollen, and houses swinging in the wind could cause them to fall off or be crushed by moving pollen balls (when too dry they can shift). At least that’s the word on the street. Perhaps a more important reason to keep the house stable is that mason bees likely find it challenging to land on a moving nest. If you have a mason bee house that is designed to hang, just get creative and attach it somehow so the bees have an easier time landing.

9. Nesting material is impermeable to water

Like anything that’s alive, mason bee eggs, larvae, and pupae produce water during respiration. When that moisture can’t escape the bees are likely more susceptible to bacterial and fungal pathogens. Plus the pollen ball itself can rot. So avoid houses that use plastic, glass, or metal tubes.

10. Nests are too shallow

The house pictured at the top of the page is approximately 2″ deep, and that could lead to most of the progeny being males. In nature, mason bees lay fertilized eggs (which develop into females) at the backs of long nests, then pack the front with unfertilized eggs (which develop into males). This means that houses with short nests can end up being primarily nurseries for worthless guys (sorry, guys). If you want a house that can generate an ecologically useful proportion of females, buy houses with nesting tubes that are approximately 6″ (152 mm). Having shorter tubes (say 4″) might be OKish but you may have far fewer females. Shorter tubes are of course fine for smaller species of solitary bees that live in smaller-diameter tunnels.

11. Contains pine cones and other fillers

Solitary bees don’t utilize pine cones. Companies cram them into insect houses because pine cones are cheap and people regard them as chic. The only thing that seems to be common in pine cones out in the wild are spiders. Similarly, cramming moss, bark, and pine needles might be evocative of nature and a simple life, but they do nothing for the bees as far as I can tell.

12. Contains holes that lead to empty cavity

This is yet another way to save money. Solitary bees use tunnels, not rooms.

13. Contains slits for butterflies

Solitary bees will not use these slits and neither will butterflies. Again, companies incorporate them to save on wood and labor, plus to influence buyers who are fond of butterflies. Don’t be fooled.

14. Honey bee shown on packaging

A photograph of a honey bee on the label is a likely sign that the house is probably not up to code. I.e., if company doesn’t know the difference between honey bees and solitary bees the house is likely to have multiple design flaws.

Mason bee house with honey bee drawing

15. Too many nesting units

When thousands of mason bees are living in close proximity, parasitic insects and mites will likely have an easier time infecting numerous nests. There’s not a huge literature on how risk scales with nest density, but please see Groulx and Forrest 2017 and Groulx and Forrest 2018 for overview of potential issue. It could also be the case that large hotels get taken over by aggressive (invasive, introduced) bees at the expense of local bees (e.g., as discussed in Maclvor and Packer 2015). My 2 cents: if your heart is set on an eye-catching mega-complex, just be extra sure that all components are truly cleanable or disposable. It’s worth emphasizing that you need to actually clean it, too, not just set it up as cleanable.

These look soooo cute, but if ALL the blocks are left in place for multiple years they could become towers filled with bee parasites.

16. Inadequate instructions

Even if you buy a good bee house and generally know things about the needs of solitary bees (mud, leaves, lots of native plants, etc.), you can still benefit from detailed instructions from somebody who thinks about solitary bees all day long. E.g., look for instructions that tell you how to clean the hotel in between seasons.

Flow chart for making buying decision

Here’s a summary flow chart to print and keep in your wallet so you’re prepared when you see something adorable. Or print and give to that shop owner who carries trap houses.

“OMG I own a death trap what should I do?”

If you have a cheapo mason bee house that saddens you, don’t do anything rash. Just leave it up and let your current residents do their thing. But at the end of the season, after all the holes are filled, put it in an unheated shed or garage for the winter (so that birds don’t feast on the pupae). In early spring, put the whole house inside of a cardboard box (here’s an image of durable emergence box). Poke a small hole in the top or side so that emerging bees see the light and escape through that hole, and then set it outside in a place where it will stay dry. After all the bees finish emerging (summer), throw out the house. Or, better yet, burn it so that I can use it here, like this guy did:

“I want a cute bee house but not the commitment”

If you want the look of a bee hotel but don’t want all the maintenance fuss, print this photograph onto a large piece of paper and mount onto a board. Viewed from a distance your neighbors will think you have the real thing. To make it last, laminate or apply a coat of clear varnish.

Free bee housing for the lazy

The BEST way to encourage lots of native bees in your yard is to just stop overdoing the yard work. Make a pile of stems from last year’s perennial garden somewhere in yard, and they’ll naturally break apart and be found by solitary bees — Monarda and Asclepias are some of the many perennials that are hollow. And leave dead trees (or logs) so that boring beetles do their thing and leave nice tunnels for the bees. Finally, leave some patches of your flower beds unmulched so that ground-nesting bees have some ground.

Where to find GOOD mason bee housing

Here’s my non-exhaustive list of companies that appear to make good mason bee hotels. Or, make your own. Below is a pic of the one I made and placed in my front yard. I have a second one in my back yard.

37 thoughts on “The horrors of mass-produced bee houses

  1. Cat Cameron-Pazera

    Thank you! I got a big, wooden bee house from Costco. It won’t be used after this year (unless I can get the bamboo out), and I’ll bee sure to follow your advice in the future.

    Can I use sunflower stems as bee houses?

    1. Toni Stahl

      This is a great article. Here is an idea: Nature’s Best Hope, the book by Douglas Tallamy, recommends building a few small Houses, with 4 or 5 tunnels each, and scattering them in different places in our yards. I also read a 3-year study you might be interested in that concludes that wasps occupy almost 3/4 of the house: Have you had problems with wasps? Will you email me your thoughts? Thank you.

  2. Pingback: Guide To Properly Constructed Mason Bee Houses – Kamloops Naturalist Club

  3. Pingback: Should I buy a bee-hotel for wild bees? | Vatorex

  4. Pingback: Soll ich ein Wildbienen-Hotel kaufen? | Vatorex

  5. Pingback: Spring Awakening: Our Backyard Bees – Johnson County Conservation – Nature Notes

  6. Sheila

    I did buy a Costco beehouse last year. A few of the tubes had the ends masoned and in the Fall I placed it in the unheated garage. Now I don’t know what to do. The tubes are solid in there and so there is no through way…Now should I try and poke the dried masonry mud out or just leave it and hope for the best ?

    1. Rick

      Hi Sheila. Leave it. Try the cardboard box method and place a new better built bee house in the old ones place. Let me know if I can help.

  7. Pingback: The Yard List(s), Part 14 | BugTracks

  8. Pingback: ACT For Bees Mid Winter Buzz - Act for Bees

  9. Pingback: Poor Bees. – Our little garden

  10. Kristina

    Hello Colin,

    This post, features some products for which I manage for my company in your photos . I wanted to reach out to you, since our product was in the photos to explain how we have improved our product offering over the past year and a half. Below you will find my response to each of the call outs that were made about how mass produced bee habitats could be killing the bees. You will also find in my response how we as a company have strengthened our knowledge in what are the best practices for developing and producing our bee habitats.

    1. Nesting blocks, tubes, reeds are not removable AND 8. Nesting material is impermeable to water
    – We offer a variety of different types of nesting tubes for our customers. We have been offering primarily bamboo tubes up to this point. Last year we introduced a removable tray design, which we saw a lot of interest in. Therefore for this year we are expanding on the removable tray designs as well as introducing a paper/cardboard tube style. We have written up training materials for our retailers and end consumers, in order for them to be well educated on the how to’s. For all styles, but specifically styles with bamboo tubes, we emphasis the importance of cleaning the habitat after each season. We have started recommending that each customer purchase 2 habitats so that they can be switched out between seasons. We found that this was helpful to limit parasites.
    2. Inadequate instructions
    – In October 2017, we purchased a company who was offering bee habitats to end consumers and key accounts. With this acquisition, we learned a lot about bee and insect habitats from our colleagues. One of the things that we learned was the importance of adequate and detailed instructions. With our new release, we updated all of our habitat packaging to include instructions, tips, and why. Since this change we continually enforce the detailed instructions on all of our new habitat designs and current.
    3. Nesting tubes open at back
    – All of our designs have a back wall to cap off the back of the nesting tubes.
    4. Reeds or holes with large splinters AND 5. Stems blocked at front
    – We have recently consolidated our bee and insect habitats to a main source for producing our products. This vendor is professional in bee habitats and is actually a vendor for Costco’s bee habitats. We are consistently doing quality checks of the product and audits of the products to ensure there are no issues, such as blockage of the nesting tubes or sharp edges.
    6. Roof lacks overhang
    – All of our current designs and new designs have a roof overhang to protect the nesting tubes from climate.
    7. House attaches to tree with string or hook
    – All current and future bee habitats that we offer must be mounted.
    9. Nests are too shallow
    – All of the designs that we currently offer and will continue to offer in the future have tubes that are at least 5-6″ deep to allow for female bee eggs.
    10. Too many nesting units
    – We do not and do not plan to offer large multiplex habitats. We do offer small scale multi habitats but emphasize the importance of cleaning after each season.
    11. Honey bee shown on packaging
    – Several years ago, the manager at the time was not aware of this. We have since updated our packaging (see point #2) and our knowledge on mason bees.

    I hope that you can see that we are trying to do the right thing and help the bee population. We hope that we will gain your support with all the of updates that we have made to our product offering.

    Thank you for your time.

    1. Julie North

      Kudos on going the extra mile in upgrading an adjusting your products. It takes integrity and humility to see a concern, review it, and then make positive changes. Looking forward to checking out your products and thank you for addressing the concerns.

  11. Brenda

    Kristina, Thank you so much for your post.

    The book shares how to build bee houses.
    Thanks, Brenda

  12. Brenda

    I recommend this book: A Guide to North American Bees. Joseph S. Wilson & Olivia Messinger Carril

    I purchased one a few years ago for $35 The book contains instructions for bee houses.

  13. Shawn McMurtry

    What chemicals do Terminix use please?? After reading your article about mosquito treatments, I printed it to share w others. My backyard neighbors recently had Terminix out in January for- per the tech, spiders, ants & centipedes – oh dear God- 3’ from my milkweed, bird baths/ nesting boxes/ hummingbird plants/ habitat certified tiny yard. I was sure to school him on what birds eat/ hummingbirds included after 3,000 miles of migration! I then attempted to unveil the active ingredients to send a note to my neighbors- about the risk to their 2 dogs/ kids…The tech could not share that info.
    After 3 days/ 6+ calls to unveil the active ingredients, getting transferred around, I finally gave up & lectured the young man assigned to fool/ foil me about the harm/ urged him to watch The Pollinators film, and begged him to consider the future for his children / grand babies. What do you know?

    1. Colin Purrington Post author

      Terminix has several different formulations so you’d have to ask your neighbor which one. They have an ATSB, for example, that has garlic oil. But they also use pyrethroids, I suspect, because that’s what everyone uses to kill mosquitoes. I poke around on the internet this morning and found this lawsuit, and it indicates that Terminix uses (or used) something called Tempo SC Ultra, which contains beta cyfluflin. I posted the question on Twitter and I’ll update if I hear any details.

  14. James Ullrich

    The original “The Orchard Mason Bee”, book by Brian Griffin has been recognized as the Bible of Mason Bee information. Written with help from Dr Philip Torchio USDA lab at University of Southern Utah, and entomologists from Washington State University.
    Updated and still current as Brian tracks all new issues that apply to maintaining your Mason Bee shelters.

  15. Phil Nuckols

    Last year I used a bee house I bought from Lowe’s before I did the research. My bad. It didn’t work out well.
    This year I made my own and used reeds from Crown Bees and bought their bees as well. So far, so good.
    I have a post on my blog about my bee raising. I’d appreciate you checking it out and let me know what you think.
    Keep up the good work on educating the public.

    1. Rick Rideabout

      Crown Bees also publishes a monthly newsletter full of timely information and detailed to-do instructions for the coming period.

  16. Phil Nuckols

    Sadly (for me) my blog is no longer online. In the year it was up, only two people commented on anything, Colin being one. I wish there had been more to justify the cost of running it. It was a hobby blog and not a money making one. I enjoyed doing it and would have been happy to keep it up if I could have gotten more people to interact. Bad marketing, I guess, but I was mainly relying on search engines to do it.

  17. Valerie

    Looking at your home-made bee house in your front yard (in your photo), it appears that some of the tunnels (the white ones) are made of plastic. Is that so, and does that violate your rule about not using plastic for the tunnels? I expanded your photo and the tunnels are very white, which makes me think they are plastic. I hope I am wrong! :)

    1. Colin Purrington Post author

      Hi Valerie. They are all paper straws that I picked up at various stores. I’ve never tried a plastic straw but have seen photographs of the in use and they tend to be used by bees who then regret their poor life decisions … the cells rot.

  18. Valerie

    Ok thanks for the info. I just cancelled my online Bee House order on a separate online ordering website based on the info I read in your blog, because I now know it is poorly designed. I will continue to research. Thanks.

  19. Tim

    Are mites guaranteed, such that the whole cleaning cycle is required? Or is it climate/region dependent? We put up a plastic house with what seems to be cardboard tubes last year, and it seems like it’s used by bees. If it indeed is a death trap, I’d surely clean it out, but I’d like to inspect for signs of mites first (though I’d imagine it would be a bit of a chore with a microscope).

    Separate question – when is the ideal time that I can assume the house is empty, for a cleaning? You mention “spring”, but spring can mean different times of the year to different people.

    1. Colin Purrington Post author

      I’m not sure there’s research on the issue, but my guess is that mites are absolutely going to build up when a house is not cleaned for several years. If this winter (anytime between Nov and Mar) you unwrap some of those cardboard tubes on a white surface you’ll be able to see mites crawling around if they are there. If you see them, just put all the mason bee cocoons into a dilute bleach solution to kill the mites. Then stock your house with fresh tubes. Oh, and if you can, line the cardboard tubes with paper straws … they are much easier to unwrap. If you do the above, don’t hesitate to send me pics if you need guidance on what you find. Good luck!


Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.