- Sugar trap. I was optimistic about this one: Dumping a quarter cup of sugar into an open mason jar, then filling the jar halfway with water. The hypothesis is that the flies are attracted to the sugar, then fall into the jar and drown. But I guess the flies here laugh in the face of such low-tech devices, instead preferring to walk down the sides of the jar, sip the nectar and fly out. Two fell in, though. Bottom line: Doesn't really work.
- Dish soap trap. Instead of sugar, pour an inch of liquid dish soap directly into the jar, then add another inch of water. This worked nicely to trap flies. However, not all liquid dish soap fared well. A floral scent didn't attract flies to the trap, but a green apple scent beckoned the flies to their doom. Definitely go for a fruit scent. Bottom line: This works. Be sure to use a fruit-scented dish soap.
Other methods were tried and rated for their effective as well. Link -via Breakfast Links
(Image credit: Flickr user Refracted Moments™)
If I get fruit flies coming in on produce I'll put a drop of dish detergent in a small dish of cider vinegar or wine vinegar.
I doubt you would need an inch of detergent as mentioned above. A few drops would be perfectly adequate to lower the surface tension of the water.