A little late but..
We had them real bad this year along with buffalo gnats which are just as evil. Search blue solo cup sticky traps. Noticeable difference in one day. By the next weekend fly bites were eliminated. I hung four from tree branches, those got more buffalo gnats. The other three that did strongest on the deer flies were lawn/leaf bag on 2 100lb propane tanks to simulate a moving body and a blue solo cup head. One was just a post with a bag/cup.
For you naysayers- As far as attracting them, if they found your trap, they were already looking for you. The biting flies are purely visual hunters that key in on movement and dark colors.
Next berry picking season I will probably be using a sticky blue hardhat!
Tanglefoot trap adhesive is the glue.
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