I was
plagued by them and my hubby took drastic measures and hunted down the hive. You can follow them and pretty easily find the nest. It was in the open meadows and was just a hole in the ground (they often use old mouse nests) but while all the grasses around here are dead
the entrance was GREEN. The moisture from their activities was enough to keep the grass alive. Very interesting... We went for the pint of gasoline poured into the nest and sealed over with dirt. I also have
many disposable water based traps that work awesome. There are a few different ways to eliminate them, a quick google search will turn up some of the best. Remember, if you use fuel - don't light it! It is the fumes that kill them. The reduction in yellow jacket traffic,and robbing was immediate.
Look at what they did to my grapes last year! Maybe now this year won't be so bad, i hate those buggers. Did you know they are considered beneficial? Psh!