Does DEET bug spray damage fly line and scare trout — what insect repellent should trout anglers use?

Yes to both: buy 20 % picaridin lotion or wipes. DEET is a plasticizer: it softens and hazes fly-line coatings, monofilament, soft plastics, lure paint and sunglass frames, while picaridin leaves plastics alone. Keith Jones's Berkley work found bass strongly repelled by DEET at about one part per million, and trout are more scent-sensitive than bass; the 1956 L-serine finding showed salmon alarmed by plain human hand-rinse at extreme dilution. Treat clothing with permethrin at home and let it dry — never streamside, because wet permethrin is highly toxic to fish and to the aquatic insects trout eat. A head net keeps repellent off the hands entirely. Trout gear is the most DEET-vulnerable: the fly line sliding through your fingers on every cast, light tippet that cannot spare any strength, soft beads and trout worms. Apply with the back of the hand.

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