We have also had lots of yellow jackets in SW Missouri.
 
I was concerned that some of my weaker colonies might be attacked so I
made a few traps.  I used buckets with tight lids or jars or whatever and
by T & E (trial and error) discovered that a 16D sinker nail would allow
the YW's to enter buy not the bees.  I baited with some old honey that I
diluted.  The bees somehow get too much of the mixture on them and very few
make it out of the trap.  I assume that almost anyting sweet would work.
 
I assume a wetting agent mixed with the dilute honey would made it
even better.
 
Try it.  You'll like it.
 
Jim Shoemaker
Brookline, MO (near Springfield and Bass Pro Shop)