Being a bee keeper I get all kinds of calls about Yellow Jackets a WASP by the way and other stinging insects. I charge $300.00 if the home owner just flat does not want to deal with them. I need to kill the wasp ASP and clean the area up so you would hardly know they were around.
I use this http://cdn.spectrumb...1121301109.ashx
It reaches 20 feet does not harm vegation and will kill any missed wasp up to 4 weeks if it is not washed down by rain watering of extra heavy dew. Try to find the entrance hole once you do go to it after it gets so dark you can just barely see, Do not use a flash lite. Spray into the entrance as best you can. As the can says will kill up to 4 weeks just by contacting it.
You were able to use the mower and trimmer fine because you were not causing vibration that bothered them, but the hedge trimmer started shaking The shrub right into the roots.
Bald faced hornets, dead in 10 minutes.