Dave, we did douse the area at night...still had a few late partyers flying around.
I didn't use anything but hornet killer because I didn't want to kill off the grass in
half my front yard! We did kill off the critters, and the next spring I had a
landscaper lay new sod over the affected area.

I think the hornets took advantage originally in a hole under the roots caused when
the tree was struck by lightning. That was the only nest I knew of within a two-block
area. I have not had any here since.

N.