How many birds are contained in that run area? And are they contained there full time? How often do you clean it out?
You suggested you are doing the 'deep litter' and if you are attempting to get it to compost naturally adding DE is detrimental, and 2" is not nearly deep enough to support...
Can't comment on DIY versions but with the commercial versions, the more the 'attractant' heats up (need a string of hot days) and the more flyies that fall in and start decaying the better they work, it takes a little time to get rolling...
I hear the timed pesticide misters work very well for outdoor or large indoor spaces...
http://www.amazon.com/Time-Mist-Dispenser-Bug-Killer/dp/B00061MT3Y
In my coop I hang NO PEST strips as well as a small bug zapper...