I got some permethrin this year to see if it helps keep ticks off. I don't know yet if it will work for ticks or gnats.
I'm sorry, I completely missed your post, which is too bad because it took another 3 hours of research to come around to Permethrin
Actually, that's only one of the three things I ended up ordering, but let me back up a bit.
On Wednesday, the problem had built to a head. I was in my yard talking to an arborist about our trees and seeing if anything needed to be done with them. While I was out there I never stopped swatting away at the horrible swarms of gnats we were getting. There must have been hundreds in the air around the two of us.
So, more determined than ever, I did a deep dive into the web and found three products:
Permethrin,
Pyrethrin, and
Nylar. That last one doesn't say Nylar anywhere, but I'm pretty sure that's what it is - it's meant to prevent the eggs from maturing into adults.
I mixed a couple tablespoons of the latter two (the Permethrin hasn't arrived yet), and sprayed the entire backyard and most of the front.
Today I stood outside for at least 15 minutes with a mug of iced tea, and I might have seen one gnat while I was out there. I'm not sure if this mixture did the whole job, but something sure did. I don't think it was just the nice weather, because my wife and I went to a show last night and the venue had a severe gnat problem outside.
Anyway, if this works, it'll be well worth the ~$70 I put into it, especially considering that a service wanted to charge me $840 for the season. I might have to refill these chemicals once or twice before the bug season is done (I need to spray at least once every two weeks), but I'll still be ahead on cost..