I've been using one of these with good success, they're not eliminated, but much less that I was having in my yard. I put 3Xs the amount of attractant on the cotton ball inside, when I just used one dose it didn't work very well at all.
Unfortunately, now they've switched to cartridges of pre-measured attractant, so I won't have the option of buying more little packs of liquid to boost my catching power. Typical, when you find something you like, they discontinue it.
RESCUE!® Reusable Yellowjacket Trap