Soap is supposed to help them drown. My experience is soap deters them, keeps them out of it.
I do not know if there is any bait that works best. All kinds of concoctions get used. Here is my bait mix that has worked well.
- sugar water 1:1, 16 oz or soda such as cola or sprite/7up diluted 50:50 with water.
- apple cider vinegar, 1 tsp
- bread yeast, 1/8 tsp
- few cubes or fillet of raw fish or basic cheapest nastiest hot dog, 1 to 2 oz
Mix enough volume to have 1-1/2 inch in bottom of the trap. The fish, suspend with line so the bottom of the fish just barely touches the liquid. Do not want the fish in the liquid. Fish works better than hot dog. Hot dog works better than anything else.
The smell of sugar draws them to the trap. The smell of protein (yeast and the fish especially) commits them into it. The smell of the cider (vinegar) repels the bees.
It is a slow start at first to get a few in. Once they are in the trap and start off gassing themselves, it becomes a YJ magnet. Like their dead bodies draws more in quicker. Do not empty the trap until you notice they are not going in anymore, it is full, or they are not getting wet not enough liquid depth left. When you clean the trap and recharge put a handful of the freshest dead back in to spike it.
When building the tub trap, if the tub size selected is large enough it works better with two funnels in the lid. More smell eminates up out of more funnels and as a result increases the trapping rate.
Hope that helps!
Let us know how it works out for you.