DEET (N ,N -diethyl-m -toluamide) Toxicity to Channel Catfish, Ictalurus punctatus , Sac Fry

Abstract

The combination of open facilities, moisture, and warm weather during channel catfish, Ictalurus punctatus, spawning season causes mosquito-infestation problems. A common solution to mosquito problems in hatcheries is to use mosquito repellents applied to exposed skin and clothing. DEET (N,N-diethyl-m-toluamide) is the active ingredient in most personal insect repellents. We determined the 24-h acute toxicity of DEET to channel catfish fry. The toxicity test consisted of 10 sac fry in three replications of six concentrations (range: 157–478 μL/L) and a control. In addition to toxicity testing, a trial was conducted to determine the amount of active ingredient dispensed from two different applicators: a pump sprayer and an aerosol can. The 24-h lethal concentration (LC10) was 274 ppm, and the 24-h LC50 was 345 ppm. The concentration required to kill 50% of the organisms was above the 100 ppm threshold to be considered practically non-toxic. The pump sprayer (98.11% active ingredient) dispensed 113.3 ± 0.57 mg (mean ± SEM) active ingredient per pump. The aerosol can (30% active ingredient) dispensed 526.8 ± 6.71 mg (mean ± standard error mean [SEM]) active ingredient per second. In hatcheries where air movement by fans is not sufficient to control mosquitoes, using insect repellent products containing DEET should be safe.