I don't have a suggestion for dealing with them, but you wouldn't believe the number of string trimmers I've had come into the shop with a complaint of not revving up, and the reason was mud daubers had stopped up the exhaust outlet.
I had this wierd premonition earlier when this thread popped up that Sparkie would have something interesting to contribute to it, and I'm relieved to find that, while true, it has nothing to do with making any kind of syrup from dirt daubers.
