I just found out about a native West Coast plant that repells flies, the Vanilla Leaf http://en.wikipedia.org/wiki/Achlys_(plant). I have seen many posts about the vanilla air freshener and I'm sure this is where it came from. I was even told companies use this plant for things like perfumes and air fresheners. People in the Northwest could probably save a lot of money collecting these themselves. They release the scent as they dry and last for weeks. I spend a lot of time foraging but never paid much attention to this one because it's not edible but I have seen it everywhere. I'm definately going to collect some to put out by the coops. We don't have a lot of flies but I hate them more than anything except earwigs. I thought I would pass this on to anyone else who might be interested.