Permethrin is a contact pesticide that kills black flies, ticks, and mosquitoes on contact but has no harmful side effects on humans if used properly. It is the active ingredient used in Buzz Off and Insect Shield clothing sold by Ex Officio and kills bugs when they land on your clothing by overloading their nervous system. You can buy Permethrin in liquid form and spray it on your own clothes to the same effect. This self-applied form lasts for 6 washings.

Permethrin is sold by Sawyer and you can by it at REI or MooseJaw. A big bottle comes with a spray adapter and will cover 4 complete sets of clothing, including shirts, pants, and socks. It’s pretty nasty stuff so you want to read the directions carefully. You need to apply it to your clothes (not the ones you are wearing) in a windless but well ventilated place like a garage. Then you let them dry for a few hours and you’re all set.

This morning, I sprayed Permethrin on a bunch of clothes that I’ll be wearing this summer when I section hike the Long Trail in Vermont, which is notorious for Black Flies. These included long sleeve shirts, convertible hiking pants, short gaiters, and some hiking socks. When you spray the Permethrin on, you want to position the sprayer 6 to 8 inches away from the clothing you plan to treat. Pay particular attention to the cuffs of long pants and shirt sleeves where the bugs will try to attack you. This is why I also sprayed my short gaiters and socks. It’s also a good idea to spray it on your hat.

Permethrin bonds to the fibres of your clothes and therefore resists washing out. In addition, you need to apply DEET to the areas of your body not covered by clothing and/or wear a bug net to create a complete black fly perimeter.

Related posts:

1. My Long Trail Black Fly Defense Strategy
2. RailRiders Eco-Mesh Shirt
3. Buff Bandanas
4. Black Fly Season
5. Trip Report: May 24-26, AT/LT, Rt.9 to Bromley Mountain