My name is Dr Margriet Dogterom and am the founder and owner of Beediverse. I write this blog for all who love bees and who want to learn more about these wonderful creatures.


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Washed mason bee cocoons

Washed and bleached mason bee cocoons


Beneficial wasp grubs


Fungi-infected blackened mason bee pupae/grubs

dsc00004 This parasitic fungi is present in most regions and infects mason bee larvae during the spring/summer months.  Decrease the presence of this parasitic fungi by first washing and scrubbing and rinsing bee homes, nesting trays AND  mason bee cocoons in water  Then- ALWAYS -give these items a final rinse with bleach (4 litres/one gallon of water with 1/4 cup of bleach).

Caution: Prevent release of fungal spores  by not breaking the blackened pupae.  More information in the book “Pollination with mason Bees“.

Along with turkeys and cranberry sauce and lots of other good things, it is time to clean your mason bee homes and cocoons.

Lots of info on our Facebook page about washing cocoons, removing mites with a sieve and storing them safely over the winter.  After washing, dry cocoons on paper towels.  Pollen feeding mites that you can remove by washing under running water have 8 legs and are just about microscopic.  You can see them fairly well with a 10 x magnifying glass.


Just sent out a Beediverse newsletter.  If you’d like a copy please let us know.


Happy thanksgiving Canada.

I really enjoyed your seminar in Courtney today and went home to open my nest only to find that about half of the cells (40+) had a 1/16″ hole drilled through the paper and cocoon. In reading your book tonight I have not found any mention of this type of predation on Mason bees would you please tell me what would do this and how to prevent it, thanks.  Alan A.

Sounds to me that these holes are the right size for parasitic wasps. These wasps parasitize the cocoon contents, and emerge as adults 3 weeks later during the summer. There are 3 ways of keeping these pests down:

1. Candling of cocoons after washing will identify parasitized cocoons and these can then be destroyed.

2. If there are large numbers during spring bee -flight, set out a sticky trap

3. Protect further parasitism after flight by placing bee nests into a wasp free net bag.

Dr Margriet

Adult parasitic wasps inside a mason bee cocoon

Fall: Adult parasitic wasps inside a mason bee cocoon.  Left alone, these adult parasitic wasps exit the cocoon and find others to parasitize.

Tiny parasitic wasp of mason bees

Spring- summer:  Tiny parasitic wasp preparing to parasitize a mason bee cocoon.


Fall:  The upper cocoon on right hand side has a hole- possibly an exit hole created by a parasitic wasp.

2013-10-06 margriet- wasp netting Mason Bee Workshop (6)

Summer-fall:  After spring bee flight, protect developing mason bees inside their nests, by placing nests into a wasp-free bag.



Fall: Cocoon contents: #3 and #4- dead bee pupae #5 parasitic wasp pupae.




Some thing was here before you could harvest your bee cocoons!  Most often these are predatory beetles,  they chew through the mud and eat whatever they can find including cocoons, pollen or developing bees.

After flight in early summer protect the nesting tunnels by turning the nest inwards.  This will prevent woodpecker damage too.dec 6holes thru mud   12 fjm 2013

Chickadees looking for a meal usually remove all the mud wall and only go in an inch or 2 into the nesting tunnel.

polen lumps

These harvested cocoons have had the mud soaked off and are now ready for washing under running water and inside a sieve. The metal scoop is pointed to a pollen lump which had been partially consumed ( irregular shape) by a young bee.

Hugh L. from Chilliwack phoned and asked why 15% of nest contents are pollen lumps and not adult bees inside their cocoons.  Pollen lumps found in the nest in the fall during cleaning time occurs  when bees die during development and can no longer consume the pollen.  The death of a developing bee can be caused by cold weather , pesticides or disease.  In this particular case it is more likely to be the effect of an extended period of cold weather in the spring.  Bee larvae can only eat and grow and develop if temperatures are warm.  Extended cold temperatures can kill off the bee larvae.  If insecticides were to blame, I would think it would be a much a higher percentage of bee larvae that are dead.  Also Hugh tells me that the nests are scattered over a 10 mile area, and again it is unlikely it is a pesticide kill for that reason.

Hugh has  lot of people excited with Mason bees in Chilliwack.  Keep up the good work Hugh.  Good to hear from you.

Dr Margriet

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