Original review: Yellow fly season has just startred in South Alabama. I purchased this kit based on other reviews. I am a believer. These pictures are less than 24 hours after installing these devices. There are approximately 3 dozen yellow flies already stuck. Time will tell if this product reduces these annoyance of these pests, but 3 dozen less is a good start.
Update: I bought 3 more balls, 2 of them have too many deer flies to count, maybe 100. I tried one in a sunny area, not so good. I moved it back under a tree.