I read in a blog the other day that washing cocoons is not necessary.
There are two good reasons for washing mason bee cocoons.
The first reason is to remove the majority if not most of the adhering mites. The washing process includes a soak in cold water to remove mud and feces. Then, cocoons are gently sprayed with cold water (while in a colander) to remove any excess mites. If excessive mites are present (even after washing) mites are removed by rolling the dry cocoons gently over a metal window screen (not plastic- it is not abrasive enough to remove mites).
The second is to remove debris and mud and feces from the cocoons so that cocoons can be candled for parasitic wasps. Candling Mason bees was first introduced and developed by Joe Sadowski from Burnaby British Columbia Canada. In a dark room, and over a bright light, parasitized cocoons can be identified, removed and destroyed. By removing these wasp parasitized cocoons, there is less of a chance for the wasp population to increase and potentially wipe out your bee population.
It is pretty neat to see what bees and other insects have been up to during the previous spring by candling cocoons and having a ‘closer look.
I recommend caring for your mason bees by harvesting and cleaning your mason bee cocoons in the fall.
|A little parasitic wasp with its ovipositor ready to insert into a
mason bee cocoon. The oblong object is a bit of bee feces
that is always on the outside of the cocoon. (photo by Hartley).