Thank you in advance for any input!
Sarah K
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I had to Google Fly Eliminators to understand what you were asking about.
Obviously, I don't have any experience myself, but extensive Googling taught me a couple of things that seemed important to any form of success, according to users as well as manufacturers.
1. there are apparently a number of different species, and you need to get hold of the specie/s that work in your particular area.
2. the wasps are tiny and don't travel more than 300 feet and since they prey on the pupae, not the adult fly, so you need to release them where the flies breed, and you need to release several times during the season since flies breeds a lot faster than these wasps.
More info at his link http://www.horsechannel.com/horse-keeping/fly-control-parasites.aspx
They talk about Fly predators, but it is more or less the same thing (I think!).
And maybe you already knew all this, but I hope it is of some help anyway. :)