Variation in amphibian response to two formulations of glyphosate-based herbicides.

Variation in toxicity among formulations and species makes it difficult to extrapolate results to all species and all formulations of herbicides. The authors exposed larval wood frogs (Lithobates sylvaticus) from 4 populations to 2 glyphosate-based herbicides, Roundup Weed and Grass Control (R) and Roundup WeatherMax (R). The 96-h median lethal concentration values for both formulations varied among the populations (Roundup Weed and Grass Control, 0.14mg acid equivalents (a.e.)/L to 1.10mg a.e./L; Roundup WeatherMax, 4.94mg a.e./L to 8.26mg a.e./L), demonstrating that toxicity varies among the formulations and that susceptibility may differ among populations. Environ Toxicol Chem 2014;33:2628-2632. (c) 2014 SETAC