With my yogurt traps, I’m not trying to get them to drown. I’m just trying to trap them in there so I can throw the cup out. Theoretically they could get back through the holes that that they crawled in, but in practice, it’s not a problem.
How long does it take for you guys to start trapping flies with the other methods. I start getting some within the hour with the yogurt, and then by the next day, the flies are nearly gone. It’s pretty amazing.