Is this chalkbrood?

While harvesting my mason bee cocoons I came across a few of these:

Is that a case of chalkbrood?

Chalkbrood looks like a larva-cadavor shaped spore... Look at my website for pictures of. http://www.crownbees.com/chalkbrood/

The dead larva is crescent shaped and when touched, the outer shell of it breaks apart easily. This is the nasty part about leaving your mason bee nests unharvested. If the chalkbrood is left in the tube/hole, mason bees inside of the chalkbrood have to brush past it to emerge in the spring.

The chalkbrood spore is now on wall of the hole, on the outside of the house, and on blossoms nearby. 3 grains of this left in a chamber for the next season's larva to lick up will perpetuate the cycle.

Harvesting is a must if you want to increase your production.

Dave, thanks for the reply and your awesome site - it's a wonderful resource.

Would you recommend a bleach rinse for all the cocoons then, to eliminate any cross-contamination?

That's exactly what I do as we come across any chalkbrood. EVERYTHING that touched it, the trays, the counter, any tools, our sieves, rock tumblers, etc. are all dunked into a 1 cup to 1 gallon tub of bleach water. Rinsed, and then dried. All cocoons are as well. The bleach will kill the spore, but leave the bees fine. Don't leave the cocoons in the bleach water longer than a minute or two. Total water bath time can exceed 15 minutes, but 3 or so is fine.

Glad you're out there raising these bees Patrick. Spread the word!