[quote="Mike":3olv275v]Mason Bees are currently housed in PVC suspended on a limb in a cherry tree. There is to be a spray done soon of all my fruit trees. How do I protect the bees?[/quote:3olv275v]

The only thing I can think of is-
Find a container large enough for your mason bee "home", such as a very large pickle jar, or even a bucket...
Take them down late at night, into the bucket, and quickly cover them with a breathable cloth top, and something to fasten the cloth securely. Then store them for one day in a cool shady place while you spray... put the back the next day (at night, just as when you took them down)...

I don't know a lot about sprays, but I am assuming that whatever you are spraying would be 'mild' enough to place them back the next day...

That is the only idea I can think of.