Fungus gnats are tiny flies that infest greenhouses. Gardeners have insisted that Bounce fabric sheets tucked into their pockets repel the pesky gnats. Fact or urban legend?
Ray Cloyd checked it out in his lab and indeed their is a repellent effect. The laundry sheets contain linalool and beta-citronellol, chemicals known to have repellent properties.
Rather than trap the gnats on yellow sticky cards, gardeners have the option to Bounce them out of the greenhouse.
Living With Insects Blog 