One of our buses was parked late last fall with a window slightly opened.  As the weather has warmed up, I'm starting to see more and more wasps on the bus. I can't find the nest, but I suspect it is in the rear heater housing (based on where they seem to originate). Can I safely treat the infestation, or do I need to call a professional for this inaccessible nest?

More on wasp problem on bus