Looking on the internet I found these solutions...
- Fan. This ended up being my favorite way to deter flies from getting anywhere near you, indoors or out. Get a big box fan and place it by the screened window, so the cooled air is directed towards you. To a fly, this is basically a wind tunnel. This, combined with the soap traps, effectively solved the fly problem.Bottom line: Works wonderfully to get rid of flies.
-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.
- Lavender-scented candles. This sounded like the loveliest idea for repelling flies. I had a few lavender candles that had been given to me as gifts, so I placed them on the back stairs, a picnic table and in the kitchen. The results are mixed: The candle on the picnic table adequately kept the flies away, while the ones on the stairs and in the kitchen didn't do much. However, all the candles were not the same. The one on the picnic table was a three-wick candle that had a high concentration of scented oil. The rest were smaller single-wick candles with a fainter fragrance. So I think the key here is that the extra heat generated by three flames distributed the fragrance further than a standard candle. Bottom line: This works. Just be sure to use a big, highly-fragranced candle.
Plastic bags filled with water. Though it always looks like a practical joke in progress, the local cafe swears by the fly-disorienting powers of the clear plastic bags of water suspended next to the doorways. I rarely see flies there, so I hang a plastic bag of water next to the back door (outside). In direct sunlight, the bag appeared to work in its immediate vicinity. But come twilight, the flies paid no mind to the obvious bag-of-water. Bottom line: This works if you use it during the day. (Readers suggest that adding a penny to the bag will make it work at night.)
Maybe somebody can post their results !