Diatomaceous earth will take care of the flies in both the house and barn. Make sure it is food grade.
I believe they were brought in this country to control aphids on the peach trees in Georgia. You already know the rest of the story.
The gov has screwed up this country so bad by letting all this stuff be imported and then it goes berserk. From these beetles to the jumping carp in the Mississippi to the snakes in the Everglades, not to mention the plants that don't belong here.
Your Goobermint and my Goobermint are of the same mind....They would screw up The Lords' Prayer, if they had the chance.