The yellow jackets probably moved South to get away from the murder hornets. Similar to NY people heading to FL.
Interesting theory but it probably has more to do with the warmer and drier than normal summer we have been having.
This is the time of the year when yellow jackets start getting more aggressive. I was stung a little more than a week ago while standing in our front yard. I am a bit allergic so I still have an itchy welt that does not want to heal.
It wasn't hard to find the nest... it looked like a busy airport under our front deck with wasps arriving and departing in massive numbers. The next morning I emptied an entire can of black flag into the opening. It killed quite a few that came out to greet me but had no real effect on the activity.
So the next morning I sprayed them again and caved in the opening. By the next morning they had excavated a new opening and resumed operations. So the next morning before the sun came up I dug the entire nest up. I trained a bright light on the opening to distract them. I would spray to kill the ones coming out, wait a bit for them to disperse then take out a shovel full of dirt. Then spray some more to calm down the next wave of swarming wasps. Eventually I got to the main part of the nest which was the diameter of a basketball and about 6 inches deep. I chopped it into little pieces. For several days stragglers who had been out foraging and spent the night away from home during my assault kept buzzing around but the residual poison seems to have taken care of them
It is a miracle that I didn't get stung again. All I had was long sleeves and pants and a hat with flaps to cover my ears. But I tried to be careful and the light helped to attract them in a direction away from me.