Backyard bee houses or bee hotels have become so popular that large garden distributors have started selling quickly made nesting habitats.
When these products are made from drilled blocks of wood or bamboo shoots, they actually do more harm than good for local hole-nesting bees. These companies' intentions are in the right place but they lack the knowledge of the pests and diseases that can harm bees.
In order to maintain and ensure the health of your hole-nesting bees, cocoons should be harvested in the fall or spring. Nesting materials should be openable and you should be able to open the materials safely, without causing harm to the bee cocoons or larvae. Dave Hunter, founder and owner of Crown Bees made this short educational video about the hidden dangers of bamboo tubes.
Bamboo that is left intact becomes a harboring ground for pollen mites and chalkbrood. You cannot clean out pollen mites or chalkbrood spores from an intact bamboo shoot or drilled block of wood. Pollen mites can kill mason bee larva by outcompeting and eating the pollen loaf before the larva has a chance. Chalkbrood is a deadly fungal infection that spreads easily between tightly-packed, unopened nesting holes. You can't tell if you have an infestation of pollen mites or chalkbrood if you don't open your nesting holes.
Many bamboo bee houses solve the problem of loose bamboo tubes by simply gluing bamboo tubes to the back of the bee house. There is no easy way for you to refresh your nesting materials. The bamboo tubes can also be cut right at the growing node and now the nesting hole is too shallow to attract any female bee. She is looking for a nesting hole that is long enough for her to lay a certain ratio of female to male bee eggs and she can't do this in a shallow nesting hole.
Bamboo tubes are also not typically measured to be the right diameter for hole nesting bees. We've seen bamboo tubes that were large enough for a frog to sit inside - these tubes are much too big for any bee to nest within. Hole-nesting bees also prefer the nesting tube to be closed off at the back end and if it's open the eggs laid in the back are vulnerable to attack by parasitic wasps.
Lastly, bamboo shoots commercially sold have walls that are too thick to open safely. You may hurt yourself or your bees as you try to open the shoot and harvest cocoons. Bamboo is a natural material but it is an exotic plant that our North American native bees did not evolve to nest within. The goal of these large suppliers is to sell a product that fits the trend of the phrase "save the bees", but if you really, truly, want to save the bees, give them nesting habitat that is well designed with the health and safety of the bees in mind.
We need your help with spreading awareness about the hidden dangers of bamboo for our native bees. Our native bees deserve the best homes and they need us to know what keeps them safe.