Mason, Crown Bees

Asked May 14, 2019, 4:24 PM EDT

A large number of my bees did not hatch this year. When opening the cocoons I found some to be immature, smaller than normal, yellow/orange in color looking like they didn't finish growing. Others were all black but hairless and immature looking. I even had some hatch and die or get their heads out of the cocoon and die.
In August I brought the tubes into the garage for winter hoping to have fewer insects invading the nesting boxes.
Any clues, weather, garage? thank you for your time and expertise.

Clackamas County Oregon mason bees

1 Response

I am really sorry to hear about your lack of success. Its always such a disappointment when bees fail to emerge. Diagnosis can be challenging with just a verbal description. Could you post some images? If the immatures died before molting into adults, it suggests they died in the spring during nest establishment. The key disease affecting mason bees - chalkbrood - kills the bees before they make a cocoon, so I suspect they died from environmental causes, perhaps excessive heat. We recommend that nests be placed in locations that get morning sun, but not excessive late-day sun for this reason. Bring your cocoons in earlier - beginning of June - to prevent wasp parasitism. When transporting the straws, carefully tip them so that the mud plugs face up and don't allow them to tip, so that larva are not knocked off their pollen balls. Finally, store the cocoons for the remainder of the summer in a location that is not excessively cold or warm, to allow the bees to complete their development. Again, attach some images to help us figure out what is going on and check out our Extension publication for other tips on mason bee husbandry: https://catalog.extension.oregonstate.edu/em9130