If you are buying mason bees this year or making your own blocks, please make sure you clean your cocoons and nesting blocks every fall. We’ve seen an increase in Houdini flies over the years and they are very harmful to mason bee populations. Look for them in the spring and try to remove them before they lay their eggs (they look like tiny flies with red eyes). They’ll lay their eggs on the mason bee pollen then eat it which starves the mason bee larvae. Pollen mites do the same thing. They eat all the pollen for the baby mason bee, but even worse, they attach themselves to the emerging bees when they crawl through the hole in spring.
Here’s a picture of the inside of nesting block and mites on a bee. You can see how many larvae the houdini fly lays and the thousands of pollen mites inside these blocks. If any of these predators are inside, they can be very harmful to mason bee populations. The best type of nesting material is the kind you can pull apart and clean every year, like stacking trays or tubes you can open and pull out cocoons and clean nesting material. Avoid bamboo tubes and holes drilled in wood, those cannot be opened to remove cocoons and clean nesting material and they become a breeding ground for evasive predators.
Please do your part to clean nesting blocks and cocoons EVERY year. If this is something you’re not able to commit too, then you can rent from us and we can do all of the cleaning for you.
If you want to see what a houdini fly looks like, you can read more about them here
To read more about how you can protect the health of solitary bees, please read Colin Purrington’s article “The Horrors of Mass-Produced Bee Houses” https://colinpurrington.com/2019/05/horrors-of-mass-produced-bee-houses/?fbclid=IwAR2CvReycUS1ctd6SPa0t25LK9nnf-mtXYF5dPxRbuq7Mc2jCnBznEKbxm8