Protect your mason bees from the tiny parasitic wasps

This is the time when parasitic wasps can produce another generation every week.  During the summer months, when temperatures  are higher than in spring and fall, these pesky little critters come out of the nest and search for new mason bee cocoons to parasitize.  I don’t know how, but these tiny adult wasps can make a tiny pin hole in the tube and crawl out and parasitize more bees.

Every July, when most bee eggs have turned into adult bees inside their cocoons, I gather all nests, set them under a veranda- where the ambient temperature is still warm.  I place two Highrises per net-bag (see wasp proof bags on my web site  They sit stacked against the wall of my home until the end of September when harvesting takes place.

I find  that net bags are successful and keep out wasp parasites.  Percent parasitism is usually not more than 5%.  If you have had trouble with these parasites, you will be pleasantly surprised with the outcome.

4 replies on “Protect your mason bees from the tiny parasitic wasps

  • Marnie Johnson

    I tried to subscribe to your blog and got an email back but when I opened it all it said was
    0A 09 0A etc with an equal sign between each. Please help. I am new to mason bees. We are having fantastic success. Our tubes are filling up rapidly. Need all the info I can get. Thanks

  • Al Mitchell

    I found one of these wasps and video taped it for hours. It may be parasitizing mason bees, but if so, it has found another nest not far from my window. Watch and tell me what is going on here. There is also a part two. And I am now video recording further work by this wasp for part 3.


    • Margriet

      pretty neat- I have watched the first video clip and I think it is a parasitic wasp. It is hairless and has a narrowing of the ‘waist’ It could be parasitizing an egg that is already inside the tunnel.


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