I hate moth balls!
I have an alternative treatment that is still in the test stage but has worked very well on my stash of wild turkey feathers for a bunch of years.
I use a gallon Zip lock bag, put a few table spoons of borax in it, insert the fletched end of 3 or 4 arrows, hold the mouth of the bag closed and shake the bag. This distributes the finer particles of borax on your feathers. Remove the arrows from the bag, give them a shake to knock off the excess borax and you are good to go.
I even bought a mortar and pestle to grind up my arrow treating borax extra fine, probably unnecessary but I like to tinker with stuff.
I have been using this treatment on my arrows about once every 6 months for the last year, no bugs even if I store them unused in a dark corner of my musty shop.
Boric acid kills feather eating beetles and repels any that may show up on your arrows for dinner.